| Message ID | ab2a4c345844f66aa22a847e522b2f4ee0786d8b.1639499239.git.baruch@tkos.co.il |
|---|---|
| State | Changes Requested |
| Delegated to: | Uwe Kleine-König |
| Headers | show |
| Series | [v10,1/3] pwm: driver for qualcomm ipq6018 pwm block | expand |
On Tue, Dec 14, 2021 at 06:27:17PM +0200, Baruch Siach wrote: > From: Baruch Siach <baruch.siach@siklu.com> > > Driver for the PWM block in Qualcomm IPQ6018 line of SoCs. Based on > driver from downstream Codeaurora kernel tree. Removed support for older > (V1) variants because I have no access to that hardware. > > Tested on IPQ6010 based hardware. > > Signed-off-by: Baruch Siach <baruch.siach@siklu.com> > --- > v10: > > Restore round up in pwm_div calculation; otherwise diff is always <= > 0, so only bingo match works > > Don't overwrite min_diff on every loop iteration > > v9: > > Address comment from Uwe Kleine-König: > > Use period_ns*rate in dividers calculation for better accuracy > > Round down pre_div and pwm_div > > Add a comment explaining why pwm_div can't underflow > > Add a comment explaining why pre_div > pwm_div end the search loop > > Drop 'CFG_' from register macros > > Rename to_ipq_pwm_chip() to ipq_pwm_from_chip() > > Change bare 'unsigned' to 'unsigned int' > > Clarify the comment on separate REG1 write for enable/disable > > Round up the period value in .get_state > > Use direct readl/writel so no need to check for regmap errors > > v7: > > Change 'offset' to 'reg' for the tcsr offset (Rob) > > Drop clock name; there is only one clock (Bjorn) > > Simplify probe failure code path (Bjorn) > > v6: > > Address Uwe Kleine-König review comments: > > Drop IPQ_PWM_MAX_DEVICES > > Rely on assigned-clock-rates; drop IPQ_PWM_CLK_SRC_FREQ > > Simplify register offset calculation > > Calculate duty cycle more precisely > > Refuse to set inverted polarity > > Drop redundant IPQ_PWM_REG1_ENABLE bit clear > > Remove x1000 factor in pwm_div calculation, use rate directly, and round up > > Choose initial pre_div such that pwm_div < IPQ_PWM_MAX_DIV > > Ensure pre_div <= pwm_div > > Rename close_ to best_ > > Explain in comment why effective_div doesn't overflow > > Limit pwm_div to IPQ_PWM_MAX_DIV - 1 to allow 100% duty cycle > > Disable clock only after pwmchip_remove() > > const pwm_ops > > Other changes: > > Add missing linux/bitfield.h header include (kernel test robot) > > Adjust code for PWM device node under TCSR (Rob Herring) > > v5: > > Use &tcsr_q6 syscon to access registers (Bjorn Andersson) > > Address Uwe Kleine-König review comments: > > Implement .get_state() > > Add IPQ_PWM_ prefix to local macros > > Use GENMASK/BIT/FIELD_PREP for register fields access > > Make type of config_div_and_duty() parameters consistent > > Derive IPQ_PWM_MIN_PERIOD_NS from IPQ_PWM_CLK_SRC_FREQ > > Integrate enable/disable into config_div_and_duty() to save register read, > and reduce frequency glitch on update > > Use min() instead of min_t() > > Fix comment format > > Use dev_err_probe() to indicate probe step failure > > Add missing clk_disable_unprepare() in .remove > > Don't set .owner > > v4: > > Use div64_u64() to fix link for 32-bit targets ((kernel test robot > <lkp@intel.com>, Uwe Kleine-König) > > v3: > > s/qcom,pwm-ipq6018/qcom,ipq6018-pwm/ (Rob Herring) > > Fix integer overflow on 32-bit targets (kernel test robot <lkp@intel.com>) > > v2: > > Address Uwe Kleine-König review comments: > > Fix period calculation when out of range > > Don't set period larger than requested > > Remove PWM disable on configuration change > > Implement .apply instead of non-atomic .config/.enable/.disable > > Don't modify PWM on .request/.free > > Check pwm_div underflow > > Fix various code and comment formatting issues > > Other changes: > > Use u64 divisor safe division > > Remove now empty .request/.free > --- > drivers/pwm/Kconfig | 12 ++ > drivers/pwm/Makefile | 1 + > drivers/pwm/pwm-ipq.c | 275 ++++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 288 insertions(+) > create mode 100644 drivers/pwm/pwm-ipq.c > > diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig > index 21e3b05a5153..e39718137ecd 100644 > --- a/drivers/pwm/Kconfig > +++ b/drivers/pwm/Kconfig > @@ -260,6 +260,18 @@ config PWM_INTEL_LGM > To compile this driver as a module, choose M here: the module > will be called pwm-intel-lgm. > > +config PWM_IPQ > + tristate "IPQ PWM support" > + depends on ARCH_QCOM || COMPILE_TEST > + depends on HAVE_CLK && HAS_IOMEM > + help > + Generic PWM framework driver for IPQ PWM block which supports > + 4 pwm channels. Each of the these channels can be configured > + independent of each other. > + > + To compile this driver as a module, choose M here: the module > + will be called pwm-ipq. > + > config PWM_IQS620A > tristate "Azoteq IQS620A PWM support" > depends on MFD_IQS62X || COMPILE_TEST > diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile > index 708840b7fba8..7402feae4b36 100644 > --- a/drivers/pwm/Makefile > +++ b/drivers/pwm/Makefile > @@ -22,6 +22,7 @@ obj-$(CONFIG_PWM_IMX1) += pwm-imx1.o > obj-$(CONFIG_PWM_IMX27) += pwm-imx27.o > obj-$(CONFIG_PWM_IMX_TPM) += pwm-imx-tpm.o > obj-$(CONFIG_PWM_INTEL_LGM) += pwm-intel-lgm.o > +obj-$(CONFIG_PWM_IPQ) += pwm-ipq.o > obj-$(CONFIG_PWM_IQS620A) += pwm-iqs620a.o > obj-$(CONFIG_PWM_JZ4740) += pwm-jz4740.o > obj-$(CONFIG_PWM_KEEMBAY) += pwm-keembay.o > diff --git a/drivers/pwm/pwm-ipq.c b/drivers/pwm/pwm-ipq.c > new file mode 100644 > index 000000000000..3764010808f0 > --- /dev/null > +++ b/drivers/pwm/pwm-ipq.c > @@ -0,0 +1,275 @@ > +// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0 > +/* > + * Copyright (c) 2016-2017, 2020 The Linux Foundation. All rights reserved. > + */ > + > +#include <linux/module.h> > +#include <linux/platform_device.h> > +#include <linux/pwm.h> > +#include <linux/clk.h> > +#include <linux/io.h> > +#include <linux/of.h> > +#include <linux/math64.h> > +#include <linux/of_device.h> > +#include <linux/bitfield.h> > + > +/* The frequency range supported is 1 Hz to clock rate */ > +#define IPQ_PWM_MAX_PERIOD_NS ((u64)NSEC_PER_SEC) > + > +/* > + * The max value specified for each field is based on the number of bits > + * in the pwm control register for that field > + */ > +#define IPQ_PWM_MAX_DIV 0xFFFF > + > +/* > + * Two 32-bit registers for each PWM: REG0, and REG1. > + * Base offset for PWM #i is at 8 * #i. > + */ > +#define IPQ_PWM_REG0 0 /*PWM_DIV PWM_HI*/ > +#define IPQ_PWM_REG0_PWM_DIV GENMASK(15, 0) > +#define IPQ_PWM_REG0_HI_DURATION GENMASK(31, 16) PWM_HI in the comment of IPQ_PWM_REG0 vs. HI_DURATION? Should this match? I'd say the comment is redundant. > +#define IPQ_PWM_REG1 4 /*ENABLE UPDATE PWM_PRE_DIV*/ > +#define IPQ_PWM_REG1_PRE_DIV GENMASK(15, 0) > +/* > + * Enable bit is set to enable output toggling in pwm device. > + * Update bit is set to reflect the changed divider and high duration > + * values in register. > + */ > +#define IPQ_PWM_REG1_UPDATE BIT(30) > +#define IPQ_PWM_REG1_ENABLE BIT(31) > + > + > +struct ipq_pwm_chip { > + struct pwm_chip chip; > + struct clk *clk; > + void __iomem *mem; > +}; > + > +static struct ipq_pwm_chip *ipq_pwm_from_chip(struct pwm_chip *chip) > +{ > + return container_of(chip, struct ipq_pwm_chip, chip); > +} > + > +static unsigned int ipq_pwm_reg_read(struct pwm_device *pwm, unsigned int reg) > +{ > + struct ipq_pwm_chip *ipq_chip = ipq_pwm_from_chip(pwm->chip); > + unsigned int off = 8 * pwm->hwpwm + reg; > + > + return readl(ipq_chip->mem + off); > +} > + > +static void ipq_pwm_reg_write(struct pwm_device *pwm, unsigned int reg, > + unsigned int val) > +{ > + struct ipq_pwm_chip *ipq_chip = ipq_pwm_from_chip(pwm->chip); > + unsigned int off = 8 * pwm->hwpwm + reg; > + > + writel(val, ipq_chip->mem + off); > +} > + > +static void config_div_and_duty(struct pwm_device *pwm, unsigned int pre_div, > + unsigned int pwm_div, unsigned long rate, u64 duty_ns, > + bool enable) > +{ > + unsigned long hi_dur; > + unsigned long val = 0; > + > + /* > + * high duration = pwm duty * (pwm div + 1) > + * pwm duty = duty_ns / period_ns > + */ > + hi_dur = div64_u64(duty_ns * rate, (pre_div + 1) * NSEC_PER_SEC); > + > + val = FIELD_PREP(IPQ_PWM_REG0_HI_DURATION, hi_dur) | > + FIELD_PREP(IPQ_PWM_REG0_PWM_DIV, pwm_div); > + ipq_pwm_reg_write(pwm, IPQ_PWM_REG0, val); > + > + val = FIELD_PREP(IPQ_PWM_REG1_PRE_DIV, pre_div); > + ipq_pwm_reg_write(pwm, IPQ_PWM_REG1, val); > + > + /* PWM enable toggle needs a separate write to REG1 */ > + val |= IPQ_PWM_REG1_UPDATE; > + if (enable) > + val |= IPQ_PWM_REG1_ENABLE; > + ipq_pwm_reg_write(pwm, IPQ_PWM_REG1, val); > +} > + > +static int ipq_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, > + const struct pwm_state *state) > +{ > + struct ipq_pwm_chip *ipq_chip = ipq_pwm_from_chip(chip); > + unsigned int pre_div, pwm_div, best_pre_div, best_pwm_div; > + unsigned long rate = clk_get_rate(ipq_chip->clk); > + u64 period_ns, duty_ns, period_rate; > + u64 min_diff; > + > + if (state->polarity != PWM_POLARITY_NORMAL) > + return -EINVAL; > + > + if (state->period < div64_u64(NSEC_PER_SEC, rate)) > + return -ERANGE; NSEC_PER_SEC / rate is the smallest period you can achieve, right? Consider rate = 33333 (Hz), then the minimal period is 30000.30000300003 ns. So you should refuse a request to configure state->period = 30000, but as div64_u64(1000000000, 33333) is 30000 you don't. > + period_ns = min(state->period, IPQ_PWM_MAX_PERIOD_NS); > + duty_ns = min(state->duty_cycle, period_ns); > + > + /* > + * period_ns is 1G or less. As long as rate is less than 16 GHz this > + * does not overflow. Well, rate cannot be bigger than 4294967295 because an unsigned long cannot hold a bigger value. > + */ > + period_rate = period_ns * rate; > + best_pre_div = IPQ_PWM_MAX_DIV; > + best_pwm_div = IPQ_PWM_MAX_DIV; > + /* Initial pre_div value such that pwm_div < IPQ_PWM_MAX_DIV */ > + pre_div = div64_u64(period_rate, > + (u64)NSEC_PER_SEC * (IPQ_PWM_MAX_DIV + 1)); Hmmm, we want (pre_div + 1) * (pwm_div + 1) * NSEC_PER_SEC -------------------------------------------- <= period_ns rate , right? Resolving that for pre_div this gives: period_ns * rate pre_div <= ---------------------------- NSEC_PER_SEC * (pwm_div + 1) The term on the right hand side is maximal for pwm_div == 0 so the possible values for pre_div are 0 ... min(div64_u64(period_rate / NSEC_PER_SEC), IPQ_PWM_MAX_DIV) isn't it? If so, your algorithm is wrong as you're iterating over div64_u64(period_rate, NSEC_PER_SEC * (IPQ_PWM_MAX_DIV + 1)) ... IPQ_PWM_MAX_DIV > + min_diff = period_rate; > + > + for (; pre_div <= IPQ_PWM_MAX_DIV; pre_div++) { > + long long diff; > + > + pwm_div = DIV64_U64_ROUND_UP(period_rate, > + (u64)NSEC_PER_SEC * (pre_div + 1)); > + /* pwm_div is unsigned; the check below catches underflow */ > + pwm_div--; What underflow? DIV64_U64_ROUND_UP returns > 0 assuming period_rate > 0. So pwm_div - 1 doesn't underflow?! The task here is to calculate the biggest pwm_div for a given pre_div such that (pre_div + 1) * (pwm_div + 1) * NSEC_PER_SEC -------------------------------------------- <= period_ns rate right? This is equivalent to: period_ns * rate pre_div <= ---------------------------- - 1 (pre_div + 1) * NSEC_PER_SEC As pre_div is integer, rounding down should be fine?! > + /* > + * pre_div and pwm_div values swap produces the same > + * result. This loop goes over all pre_div <= pwm_div > + * combinations. The rest are equivalent. > + */ I'd write: /* * Swapping values for pre_div and pwm_div produces the same * period length. So we can skip all settings with pre_div < * pwm_div which results in bigger constraints for selecting the * duty_cycle than with the two values swapped. */ > + if (pre_div > pwm_div) > + break; > + > + /* > + * Make sure we can do 100% duty cycle where > + * hi_dur == pwm_div + 1 > + */ > + if (pwm_div > IPQ_PWM_MAX_DIV - 1) > + continue; > + > + diff = ((uint64_t)NSEC_PER_SEC * (pre_div + 1) * (pwm_div + 1)) > + - period_rate; > + > + if (diff < 0) /* period larger than requested */ > + continue; This shouldn't happen if the above calculation is correct. > + if (diff == 0) { /* bingo */ > + best_pre_div = pre_div; > + best_pwm_div = pwm_div; > + break; > + } > + if (diff < min_diff) { > + min_diff = diff; > + best_pre_div = pre_div; > + best_pwm_div = pwm_div; > + } This can be simplified as: if (diff < min_diff) { best_pre_div = pre_div; best_pwm_div = pwm_div; min_diff = diff; if (min_diff == 0) /* bingo! */ break; } > + } > + > + /* config divider values for the closest possible frequency */ > + config_div_and_duty(pwm, best_pre_div, best_pwm_div, > + rate, duty_ns, state->enabled); > + > + return 0; > +} > + > +static void ipq_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm, > + struct pwm_state *state) > +{ > + struct ipq_pwm_chip *ipq_chip = ipq_pwm_from_chip(chip); > + unsigned long rate = clk_get_rate(ipq_chip->clk); > + unsigned int pre_div, pwm_div, hi_dur; > + u64 effective_div, hi_div; > + u32 reg0, reg1; > + > + reg0 = ipq_pwm_reg_read(pwm, IPQ_PWM_REG0); > + reg1 = ipq_pwm_reg_read(pwm, IPQ_PWM_REG1); > + > + state->polarity = PWM_POLARITY_NORMAL; > + state->enabled = reg1 & IPQ_PWM_REG1_ENABLE; > + > + pwm_div = FIELD_GET(IPQ_PWM_REG0_PWM_DIV, reg0); > + hi_dur = FIELD_GET(IPQ_PWM_REG0_HI_DURATION, reg0); > + pre_div = FIELD_GET(IPQ_PWM_REG1_PRE_DIV, reg1); > + > + /* No overflow here, both pre_div and pwm_div <= 0xffff */ > + effective_div = (u64)(pre_div + 1) * (pwm_div + 1); > + state->period = DIV64_U64_ROUND_UP(effective_div * NSEC_PER_SEC, rate); > + > + hi_div = hi_dur * (pre_div + 1); > + state->duty_cycle = div64_u64(hi_div * NSEC_PER_SEC, rate); This must be round up for the same reasons as for period. > +} Best regards Uwe
Hi Uwe, Thanks for your detailed review and comments. Please find my comments below. On Wed, Jan 19 2022, Uwe Kleine-König wrote: > On Tue, Dec 14, 2021 at 06:27:17PM +0200, Baruch Siach wrote: >> From: Baruch Siach <baruch.siach@siklu.com> >> >> Driver for the PWM block in Qualcomm IPQ6018 line of SoCs. Based on >> driver from downstream Codeaurora kernel tree. Removed support for older >> (V1) variants because I have no access to that hardware. >> >> Tested on IPQ6010 based hardware. >> >> Signed-off-by: Baruch Siach <baruch.siach@siklu.com> >> --- >> v10: >> >> Restore round up in pwm_div calculation; otherwise diff is always <= >> 0, so only bingo match works >> >> Don't overwrite min_diff on every loop iteration >> >> v9: >> >> Address comment from Uwe Kleine-König: >> >> Use period_ns*rate in dividers calculation for better accuracy >> >> Round down pre_div and pwm_div >> >> Add a comment explaining why pwm_div can't underflow >> >> Add a comment explaining why pre_div > pwm_div end the search loop >> >> Drop 'CFG_' from register macros >> >> Rename to_ipq_pwm_chip() to ipq_pwm_from_chip() >> >> Change bare 'unsigned' to 'unsigned int' >> >> Clarify the comment on separate REG1 write for enable/disable >> >> Round up the period value in .get_state >> >> Use direct readl/writel so no need to check for regmap errors >> >> v7: >> >> Change 'offset' to 'reg' for the tcsr offset (Rob) >> >> Drop clock name; there is only one clock (Bjorn) >> >> Simplify probe failure code path (Bjorn) >> >> v6: >> >> Address Uwe Kleine-König review comments: >> >> Drop IPQ_PWM_MAX_DEVICES >> >> Rely on assigned-clock-rates; drop IPQ_PWM_CLK_SRC_FREQ >> >> Simplify register offset calculation >> >> Calculate duty cycle more precisely >> >> Refuse to set inverted polarity >> >> Drop redundant IPQ_PWM_REG1_ENABLE bit clear >> >> Remove x1000 factor in pwm_div calculation, use rate directly, and round up >> >> Choose initial pre_div such that pwm_div < IPQ_PWM_MAX_DIV >> >> Ensure pre_div <= pwm_div >> >> Rename close_ to best_ >> >> Explain in comment why effective_div doesn't overflow >> >> Limit pwm_div to IPQ_PWM_MAX_DIV - 1 to allow 100% duty cycle >> >> Disable clock only after pwmchip_remove() >> >> const pwm_ops >> >> Other changes: >> >> Add missing linux/bitfield.h header include (kernel test robot) >> >> Adjust code for PWM device node under TCSR (Rob Herring) >> >> v5: >> >> Use &tcsr_q6 syscon to access registers (Bjorn Andersson) >> >> Address Uwe Kleine-König review comments: >> >> Implement .get_state() >> >> Add IPQ_PWM_ prefix to local macros >> >> Use GENMASK/BIT/FIELD_PREP for register fields access >> >> Make type of config_div_and_duty() parameters consistent >> >> Derive IPQ_PWM_MIN_PERIOD_NS from IPQ_PWM_CLK_SRC_FREQ >> >> Integrate enable/disable into config_div_and_duty() to save register read, >> and reduce frequency glitch on update >> >> Use min() instead of min_t() >> >> Fix comment format >> >> Use dev_err_probe() to indicate probe step failure >> >> Add missing clk_disable_unprepare() in .remove >> >> Don't set .owner >> >> v4: >> >> Use div64_u64() to fix link for 32-bit targets ((kernel test robot >> <lkp@intel.com>, Uwe Kleine-König) >> >> v3: >> >> s/qcom,pwm-ipq6018/qcom,ipq6018-pwm/ (Rob Herring) >> >> Fix integer overflow on 32-bit targets (kernel test robot <lkp@intel.com>) >> >> v2: >> >> Address Uwe Kleine-König review comments: >> >> Fix period calculation when out of range >> >> Don't set period larger than requested >> >> Remove PWM disable on configuration change >> >> Implement .apply instead of non-atomic .config/.enable/.disable >> >> Don't modify PWM on .request/.free >> >> Check pwm_div underflow >> >> Fix various code and comment formatting issues >> >> Other changes: >> >> Use u64 divisor safe division >> >> Remove now empty .request/.free >> --- >> drivers/pwm/Kconfig | 12 ++ >> drivers/pwm/Makefile | 1 + >> drivers/pwm/pwm-ipq.c | 275 ++++++++++++++++++++++++++++++++++++++++++ >> 3 files changed, 288 insertions(+) >> create mode 100644 drivers/pwm/pwm-ipq.c >> >> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig >> index 21e3b05a5153..e39718137ecd 100644 >> --- a/drivers/pwm/Kconfig >> +++ b/drivers/pwm/Kconfig >> @@ -260,6 +260,18 @@ config PWM_INTEL_LGM >> To compile this driver as a module, choose M here: the module >> will be called pwm-intel-lgm. >> >> +config PWM_IPQ >> + tristate "IPQ PWM support" >> + depends on ARCH_QCOM || COMPILE_TEST >> + depends on HAVE_CLK && HAS_IOMEM >> + help >> + Generic PWM framework driver for IPQ PWM block which supports >> + 4 pwm channels. Each of the these channels can be configured >> + independent of each other. >> + >> + To compile this driver as a module, choose M here: the module >> + will be called pwm-ipq. >> + >> config PWM_IQS620A >> tristate "Azoteq IQS620A PWM support" >> depends on MFD_IQS62X || COMPILE_TEST >> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile >> index 708840b7fba8..7402feae4b36 100644 >> --- a/drivers/pwm/Makefile >> +++ b/drivers/pwm/Makefile >> @@ -22,6 +22,7 @@ obj-$(CONFIG_PWM_IMX1) += pwm-imx1.o >> obj-$(CONFIG_PWM_IMX27) += pwm-imx27.o >> obj-$(CONFIG_PWM_IMX_TPM) += pwm-imx-tpm.o >> obj-$(CONFIG_PWM_INTEL_LGM) += pwm-intel-lgm.o >> +obj-$(CONFIG_PWM_IPQ) += pwm-ipq.o >> obj-$(CONFIG_PWM_IQS620A) += pwm-iqs620a.o >> obj-$(CONFIG_PWM_JZ4740) += pwm-jz4740.o >> obj-$(CONFIG_PWM_KEEMBAY) += pwm-keembay.o >> diff --git a/drivers/pwm/pwm-ipq.c b/drivers/pwm/pwm-ipq.c >> new file mode 100644 >> index 000000000000..3764010808f0 >> --- /dev/null >> +++ b/drivers/pwm/pwm-ipq.c >> @@ -0,0 +1,275 @@ >> +// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0 >> +/* >> + * Copyright (c) 2016-2017, 2020 The Linux Foundation. All rights reserved. >> + */ >> + >> +#include <linux/module.h> >> +#include <linux/platform_device.h> >> +#include <linux/pwm.h> >> +#include <linux/clk.h> >> +#include <linux/io.h> >> +#include <linux/of.h> >> +#include <linux/math64.h> >> +#include <linux/of_device.h> >> +#include <linux/bitfield.h> >> + >> +/* The frequency range supported is 1 Hz to clock rate */ >> +#define IPQ_PWM_MAX_PERIOD_NS ((u64)NSEC_PER_SEC) >> + >> +/* >> + * The max value specified for each field is based on the number of bits >> + * in the pwm control register for that field >> + */ >> +#define IPQ_PWM_MAX_DIV 0xFFFF >> + >> +/* >> + * Two 32-bit registers for each PWM: REG0, and REG1. >> + * Base offset for PWM #i is at 8 * #i. >> + */ >> +#define IPQ_PWM_REG0 0 /*PWM_DIV PWM_HI*/ >> +#define IPQ_PWM_REG0_PWM_DIV GENMASK(15, 0) >> +#define IPQ_PWM_REG0_HI_DURATION GENMASK(31, 16) > > PWM_HI in the comment of IPQ_PWM_REG0 vs. HI_DURATION? Should this > match? I'd say the comment is redundant. > >> +#define IPQ_PWM_REG1 4 /*ENABLE UPDATE PWM_PRE_DIV*/ >> +#define IPQ_PWM_REG1_PRE_DIV GENMASK(15, 0) >> +/* >> + * Enable bit is set to enable output toggling in pwm device. >> + * Update bit is set to reflect the changed divider and high duration >> + * values in register. >> + */ >> +#define IPQ_PWM_REG1_UPDATE BIT(30) >> +#define IPQ_PWM_REG1_ENABLE BIT(31) >> + >> + >> +struct ipq_pwm_chip { >> + struct pwm_chip chip; >> + struct clk *clk; >> + void __iomem *mem; >> +}; >> + >> +static struct ipq_pwm_chip *ipq_pwm_from_chip(struct pwm_chip *chip) >> +{ >> + return container_of(chip, struct ipq_pwm_chip, chip); >> +} >> + >> +static unsigned int ipq_pwm_reg_read(struct pwm_device *pwm, unsigned int reg) >> +{ >> + struct ipq_pwm_chip *ipq_chip = ipq_pwm_from_chip(pwm->chip); >> + unsigned int off = 8 * pwm->hwpwm + reg; >> + >> + return readl(ipq_chip->mem + off); >> +} >> + >> +static void ipq_pwm_reg_write(struct pwm_device *pwm, unsigned int reg, >> + unsigned int val) >> +{ >> + struct ipq_pwm_chip *ipq_chip = ipq_pwm_from_chip(pwm->chip); >> + unsigned int off = 8 * pwm->hwpwm + reg; >> + >> + writel(val, ipq_chip->mem + off); >> +} >> + >> +static void config_div_and_duty(struct pwm_device *pwm, unsigned int pre_div, >> + unsigned int pwm_div, unsigned long rate, u64 duty_ns, >> + bool enable) >> +{ >> + unsigned long hi_dur; >> + unsigned long val = 0; >> + >> + /* >> + * high duration = pwm duty * (pwm div + 1) >> + * pwm duty = duty_ns / period_ns >> + */ >> + hi_dur = div64_u64(duty_ns * rate, (pre_div + 1) * NSEC_PER_SEC); >> + >> + val = FIELD_PREP(IPQ_PWM_REG0_HI_DURATION, hi_dur) | >> + FIELD_PREP(IPQ_PWM_REG0_PWM_DIV, pwm_div); >> + ipq_pwm_reg_write(pwm, IPQ_PWM_REG0, val); >> + >> + val = FIELD_PREP(IPQ_PWM_REG1_PRE_DIV, pre_div); >> + ipq_pwm_reg_write(pwm, IPQ_PWM_REG1, val); >> + >> + /* PWM enable toggle needs a separate write to REG1 */ >> + val |= IPQ_PWM_REG1_UPDATE; >> + if (enable) >> + val |= IPQ_PWM_REG1_ENABLE; >> + ipq_pwm_reg_write(pwm, IPQ_PWM_REG1, val); >> +} >> + >> +static int ipq_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, >> + const struct pwm_state *state) >> +{ >> + struct ipq_pwm_chip *ipq_chip = ipq_pwm_from_chip(chip); >> + unsigned int pre_div, pwm_div, best_pre_div, best_pwm_div; >> + unsigned long rate = clk_get_rate(ipq_chip->clk); >> + u64 period_ns, duty_ns, period_rate; >> + u64 min_diff; >> + >> + if (state->polarity != PWM_POLARITY_NORMAL) >> + return -EINVAL; >> + >> + if (state->period < div64_u64(NSEC_PER_SEC, rate)) >> + return -ERANGE; > > NSEC_PER_SEC / rate is the smallest period you can achieve, right? > Consider rate = 33333 (Hz), then the minimal period is > 30000.30000300003 ns. So you should refuse a request to configure > state->period = 30000, but as div64_u64(1000000000, 33333) is 30000 you > don't. > >> + period_ns = min(state->period, IPQ_PWM_MAX_PERIOD_NS); >> + duty_ns = min(state->duty_cycle, period_ns); >> + >> + /* >> + * period_ns is 1G or less. As long as rate is less than 16 GHz this >> + * does not overflow. > > Well, rate cannot be bigger than 4294967295 because an unsigned long > cannot hold a bigger value. On 64-bit systems __SIZEOF_LONG__ is 8, which can hold more than 2^32. >> + */ >> + period_rate = period_ns * rate; >> + best_pre_div = IPQ_PWM_MAX_DIV; >> + best_pwm_div = IPQ_PWM_MAX_DIV; >> + /* Initial pre_div value such that pwm_div < IPQ_PWM_MAX_DIV */ Note this comment. >> + pre_div = div64_u64(period_rate, >> + (u64)NSEC_PER_SEC * (IPQ_PWM_MAX_DIV + 1)); > > Hmmm, we want > > (pre_div + 1) * (pwm_div + 1) * NSEC_PER_SEC > -------------------------------------------- <= period_ns > rate > > , right? Resolving that for pre_div this gives: > > period_ns * rate > pre_div <= ---------------------------- > NSEC_PER_SEC * (pwm_div + 1) > > The term on the right hand side is maximal for pwm_div == 0 so the > possible values for pre_div are > > 0 ... min(div64_u64(period_rate / NSEC_PER_SEC), IPQ_PWM_MAX_DIV) > > isn't it? I don't think so. pre_div == 0 will produce pwm_div larger than IPQ_PWM_MAX_DIV for a large period_rate value. The initial pre_div here is the smallest value that produces pwm_div within it limit. > If so, your algorithm is wrong as you're iterating over > > div64_u64(period_rate, NSEC_PER_SEC * (IPQ_PWM_MAX_DIV + 1)) ... IPQ_PWM_MAX_DIV The loop stops when pre_div > pwm_div. That should be before pre_div == IPQ_PWM_MAX_DIV because pwm_div <= IPQ_PWM_MAX_DIV. Should I put the pre_div > pwm_div condition directly in the for statement? >> + min_diff = period_rate; >> + >> + for (; pre_div <= IPQ_PWM_MAX_DIV; pre_div++) { >> + long long diff; >> + >> + pwm_div = DIV64_U64_ROUND_UP(period_rate, >> + (u64)NSEC_PER_SEC * (pre_div + 1)); >> + /* pwm_div is unsigned; the check below catches underflow */ >> + pwm_div--; > > What underflow? DIV64_U64_ROUND_UP returns > 0 assuming period_rate > 0. > So pwm_div - 1 doesn't underflow?! I'll update the comment. > The task here is to calculate the biggest pwm_div for a given pre_div > such that > > > (pre_div + 1) * (pwm_div + 1) * NSEC_PER_SEC > -------------------------------------------- <= period_ns > rate > > right? > > This is equivalent to: > > period_ns * rate > pre_div <= ---------------------------- - 1 > (pre_div + 1) * NSEC_PER_SEC > > As pre_div is integer, rounding down should be fine?! I can't follow. With round down (as in v8) the result is always: NSEC_PER_SEC * (pre_div + 1) * (pwm_div + 1) <= period_rate As a result, 'diff' calculation below will always produce diff <= 0. When there is no diff == 0 result (bingo) we get IPQ_PWM_MAX_DIV in both best_ values at the end of the loop. Do we actually need diff > 0 in the condition below? >> + /* >> + * pre_div and pwm_div values swap produces the same >> + * result. This loop goes over all pre_div <= pwm_div >> + * combinations. The rest are equivalent. >> + */ > > I'd write: > > /* > * Swapping values for pre_div and pwm_div produces the same > * period length. So we can skip all settings with pre_div < > * pwm_div which results in bigger constraints for selecting the > * duty_cycle than with the two values swapped. > */ I'll take your wording with inverted inequality sign. Thanks, baruch >> + if (pre_div > pwm_div) >> + break; >> + >> + /* >> + * Make sure we can do 100% duty cycle where >> + * hi_dur == pwm_div + 1 >> + */ >> + if (pwm_div > IPQ_PWM_MAX_DIV - 1) >> + continue; >> + >> + diff = ((uint64_t)NSEC_PER_SEC * (pre_div + 1) * (pwm_div + 1)) >> + - period_rate; >> + >> + if (diff < 0) /* period larger than requested */ >> + continue; > > This shouldn't happen if the above calculation is correct. > >> + if (diff == 0) { /* bingo */ >> + best_pre_div = pre_div; >> + best_pwm_div = pwm_div; >> + break; >> + } >> + if (diff < min_diff) { >> + min_diff = diff; >> + best_pre_div = pre_div; >> + best_pwm_div = pwm_div; >> + } > > This can be simplified as: > > if (diff < min_diff) { > best_pre_div = pre_div; > best_pwm_div = pwm_div; > min_diff = diff; > > if (min_diff == 0) > /* bingo! */ > break; > } > >> + } >> + >> + /* config divider values for the closest possible frequency */ >> + config_div_and_duty(pwm, best_pre_div, best_pwm_div, >> + rate, duty_ns, state->enabled); >> + >> + return 0; >> +} >> + >> +static void ipq_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm, >> + struct pwm_state *state) >> +{ >> + struct ipq_pwm_chip *ipq_chip = ipq_pwm_from_chip(chip); >> + unsigned long rate = clk_get_rate(ipq_chip->clk); >> + unsigned int pre_div, pwm_div, hi_dur; >> + u64 effective_div, hi_div; >> + u32 reg0, reg1; >> + >> + reg0 = ipq_pwm_reg_read(pwm, IPQ_PWM_REG0); >> + reg1 = ipq_pwm_reg_read(pwm, IPQ_PWM_REG1); >> + >> + state->polarity = PWM_POLARITY_NORMAL; >> + state->enabled = reg1 & IPQ_PWM_REG1_ENABLE; >> + >> + pwm_div = FIELD_GET(IPQ_PWM_REG0_PWM_DIV, reg0); >> + hi_dur = FIELD_GET(IPQ_PWM_REG0_HI_DURATION, reg0); >> + pre_div = FIELD_GET(IPQ_PWM_REG1_PRE_DIV, reg1); >> + >> + /* No overflow here, both pre_div and pwm_div <= 0xffff */ >> + effective_div = (u64)(pre_div + 1) * (pwm_div + 1); >> + state->period = DIV64_U64_ROUND_UP(effective_div * NSEC_PER_SEC, rate); >> + >> + hi_div = hi_dur * (pre_div + 1); >> + state->duty_cycle = div64_u64(hi_div * NSEC_PER_SEC, rate); > > This must be round up for the same reasons as for period. > >> +} > > Best regards > Uwe
Hello Baruch, On Tue, Jan 25, 2022 at 03:03:08PM +0200, Baruch Siach wrote: > On Wed, Jan 19 2022, Uwe Kleine-König wrote: > > On Tue, Dec 14, 2021 at 06:27:17PM +0200, Baruch Siach wrote: > >> From: Baruch Siach <baruch.siach@siklu.com> > >> > >> Driver for the PWM block in Qualcomm IPQ6018 line of SoCs. Based on > >> driver from downstream Codeaurora kernel tree. Removed support for older > >> (V1) variants because I have no access to that hardware. > >> > >> Tested on IPQ6010 based hardware. > >> > >> Signed-off-by: Baruch Siach <baruch.siach@siklu.com> > >> --- > >> v10: > >> > >> Restore round up in pwm_div calculation; otherwise diff is always <= > >> 0, so only bingo match works > >> > >> Don't overwrite min_diff on every loop iteration > >> > >> v9: > >> > >> Address comment from Uwe Kleine-König: > >> > >> Use period_ns*rate in dividers calculation for better accuracy > >> > >> Round down pre_div and pwm_div > >> > >> Add a comment explaining why pwm_div can't underflow > >> > >> Add a comment explaining why pre_div > pwm_div end the search loop > >> > >> Drop 'CFG_' from register macros > >> > >> Rename to_ipq_pwm_chip() to ipq_pwm_from_chip() > >> > >> Change bare 'unsigned' to 'unsigned int' > >> > >> Clarify the comment on separate REG1 write for enable/disable > >> > >> Round up the period value in .get_state > >> > >> Use direct readl/writel so no need to check for regmap errors > >> > >> v7: > >> > >> Change 'offset' to 'reg' for the tcsr offset (Rob) > >> > >> Drop clock name; there is only one clock (Bjorn) > >> > >> Simplify probe failure code path (Bjorn) > >> > >> v6: > >> > >> Address Uwe Kleine-König review comments: > >> > >> Drop IPQ_PWM_MAX_DEVICES > >> > >> Rely on assigned-clock-rates; drop IPQ_PWM_CLK_SRC_FREQ > >> > >> Simplify register offset calculation > >> > >> Calculate duty cycle more precisely > >> > >> Refuse to set inverted polarity > >> > >> Drop redundant IPQ_PWM_REG1_ENABLE bit clear > >> > >> Remove x1000 factor in pwm_div calculation, use rate directly, and round up > >> > >> Choose initial pre_div such that pwm_div < IPQ_PWM_MAX_DIV > >> > >> Ensure pre_div <= pwm_div > >> > >> Rename close_ to best_ > >> > >> Explain in comment why effective_div doesn't overflow > >> > >> Limit pwm_div to IPQ_PWM_MAX_DIV - 1 to allow 100% duty cycle > >> > >> Disable clock only after pwmchip_remove() > >> > >> const pwm_ops > >> > >> Other changes: > >> > >> Add missing linux/bitfield.h header include (kernel test robot) > >> > >> Adjust code for PWM device node under TCSR (Rob Herring) > >> > >> v5: > >> > >> Use &tcsr_q6 syscon to access registers (Bjorn Andersson) > >> > >> Address Uwe Kleine-König review comments: > >> > >> Implement .get_state() > >> > >> Add IPQ_PWM_ prefix to local macros > >> > >> Use GENMASK/BIT/FIELD_PREP for register fields access > >> > >> Make type of config_div_and_duty() parameters consistent > >> > >> Derive IPQ_PWM_MIN_PERIOD_NS from IPQ_PWM_CLK_SRC_FREQ > >> > >> Integrate enable/disable into config_div_and_duty() to save register read, > >> and reduce frequency glitch on update > >> > >> Use min() instead of min_t() > >> > >> Fix comment format > >> > >> Use dev_err_probe() to indicate probe step failure > >> > >> Add missing clk_disable_unprepare() in .remove > >> > >> Don't set .owner > >> > >> v4: > >> > >> Use div64_u64() to fix link for 32-bit targets ((kernel test robot > >> <lkp@intel.com>, Uwe Kleine-König) > >> > >> v3: > >> > >> s/qcom,pwm-ipq6018/qcom,ipq6018-pwm/ (Rob Herring) > >> > >> Fix integer overflow on 32-bit targets (kernel test robot <lkp@intel.com>) > >> > >> v2: > >> > >> Address Uwe Kleine-König review comments: > >> > >> Fix period calculation when out of range > >> > >> Don't set period larger than requested > >> > >> Remove PWM disable on configuration change > >> > >> Implement .apply instead of non-atomic .config/.enable/.disable > >> > >> Don't modify PWM on .request/.free > >> > >> Check pwm_div underflow > >> > >> Fix various code and comment formatting issues > >> > >> Other changes: > >> > >> Use u64 divisor safe division > >> > >> Remove now empty .request/.free > >> --- > >> drivers/pwm/Kconfig | 12 ++ > >> drivers/pwm/Makefile | 1 + > >> drivers/pwm/pwm-ipq.c | 275 ++++++++++++++++++++++++++++++++++++++++++ > >> 3 files changed, 288 insertions(+) > >> create mode 100644 drivers/pwm/pwm-ipq.c > >> > >> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig > >> index 21e3b05a5153..e39718137ecd 100644 > >> --- a/drivers/pwm/Kconfig > >> +++ b/drivers/pwm/Kconfig > >> @@ -260,6 +260,18 @@ config PWM_INTEL_LGM > >> To compile this driver as a module, choose M here: the module > >> will be called pwm-intel-lgm. > >> > >> +config PWM_IPQ > >> + tristate "IPQ PWM support" > >> + depends on ARCH_QCOM || COMPILE_TEST > >> + depends on HAVE_CLK && HAS_IOMEM > >> + help > >> + Generic PWM framework driver for IPQ PWM block which supports > >> + 4 pwm channels. Each of the these channels can be configured > >> + independent of each other. > >> + > >> + To compile this driver as a module, choose M here: the module > >> + will be called pwm-ipq. > >> + > >> config PWM_IQS620A > >> tristate "Azoteq IQS620A PWM support" > >> depends on MFD_IQS62X || COMPILE_TEST > >> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile > >> index 708840b7fba8..7402feae4b36 100644 > >> --- a/drivers/pwm/Makefile > >> +++ b/drivers/pwm/Makefile > >> @@ -22,6 +22,7 @@ obj-$(CONFIG_PWM_IMX1) += pwm-imx1.o > >> obj-$(CONFIG_PWM_IMX27) += pwm-imx27.o > >> obj-$(CONFIG_PWM_IMX_TPM) += pwm-imx-tpm.o > >> obj-$(CONFIG_PWM_INTEL_LGM) += pwm-intel-lgm.o > >> +obj-$(CONFIG_PWM_IPQ) += pwm-ipq.o > >> obj-$(CONFIG_PWM_IQS620A) += pwm-iqs620a.o > >> obj-$(CONFIG_PWM_JZ4740) += pwm-jz4740.o > >> obj-$(CONFIG_PWM_KEEMBAY) += pwm-keembay.o > >> diff --git a/drivers/pwm/pwm-ipq.c b/drivers/pwm/pwm-ipq.c > >> new file mode 100644 > >> index 000000000000..3764010808f0 > >> --- /dev/null > >> +++ b/drivers/pwm/pwm-ipq.c > >> @@ -0,0 +1,275 @@ > >> +// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0 > >> +/* > >> + * Copyright (c) 2016-2017, 2020 The Linux Foundation. All rights reserved. > >> + */ > >> + > >> +#include <linux/module.h> > >> +#include <linux/platform_device.h> > >> +#include <linux/pwm.h> > >> +#include <linux/clk.h> > >> +#include <linux/io.h> > >> +#include <linux/of.h> > >> +#include <linux/math64.h> > >> +#include <linux/of_device.h> > >> +#include <linux/bitfield.h> > >> + > >> +/* The frequency range supported is 1 Hz to clock rate */ > >> +#define IPQ_PWM_MAX_PERIOD_NS ((u64)NSEC_PER_SEC) > >> + > >> +/* > >> + * The max value specified for each field is based on the number of bits > >> + * in the pwm control register for that field > >> + */ > >> +#define IPQ_PWM_MAX_DIV 0xFFFF > >> + > >> +/* > >> + * Two 32-bit registers for each PWM: REG0, and REG1. > >> + * Base offset for PWM #i is at 8 * #i. > >> + */ > >> +#define IPQ_PWM_REG0 0 /*PWM_DIV PWM_HI*/ > >> +#define IPQ_PWM_REG0_PWM_DIV GENMASK(15, 0) > >> +#define IPQ_PWM_REG0_HI_DURATION GENMASK(31, 16) > > > > PWM_HI in the comment of IPQ_PWM_REG0 vs. HI_DURATION? Should this > > match? I'd say the comment is redundant. > > > >> +#define IPQ_PWM_REG1 4 /*ENABLE UPDATE PWM_PRE_DIV*/ > >> +#define IPQ_PWM_REG1_PRE_DIV GENMASK(15, 0) > >> +/* > >> + * Enable bit is set to enable output toggling in pwm device. > >> + * Update bit is set to reflect the changed divider and high duration > >> + * values in register. > >> + */ > >> +#define IPQ_PWM_REG1_UPDATE BIT(30) > >> +#define IPQ_PWM_REG1_ENABLE BIT(31) > >> + > >> + > >> +struct ipq_pwm_chip { > >> + struct pwm_chip chip; > >> + struct clk *clk; > >> + void __iomem *mem; > >> +}; > >> + > >> +static struct ipq_pwm_chip *ipq_pwm_from_chip(struct pwm_chip *chip) > >> +{ > >> + return container_of(chip, struct ipq_pwm_chip, chip); > >> +} > >> + > >> +static unsigned int ipq_pwm_reg_read(struct pwm_device *pwm, unsigned int reg) > >> +{ > >> + struct ipq_pwm_chip *ipq_chip = ipq_pwm_from_chip(pwm->chip); > >> + unsigned int off = 8 * pwm->hwpwm + reg; > >> + > >> + return readl(ipq_chip->mem + off); > >> +} > >> + > >> +static void ipq_pwm_reg_write(struct pwm_device *pwm, unsigned int reg, > >> + unsigned int val) > >> +{ > >> + struct ipq_pwm_chip *ipq_chip = ipq_pwm_from_chip(pwm->chip); > >> + unsigned int off = 8 * pwm->hwpwm + reg; > >> + > >> + writel(val, ipq_chip->mem + off); > >> +} > >> + > >> +static void config_div_and_duty(struct pwm_device *pwm, unsigned int pre_div, > >> + unsigned int pwm_div, unsigned long rate, u64 duty_ns, > >> + bool enable) > >> +{ > >> + unsigned long hi_dur; > >> + unsigned long val = 0; > >> + > >> + /* > >> + * high duration = pwm duty * (pwm div + 1) > >> + * pwm duty = duty_ns / period_ns > >> + */ > >> + hi_dur = div64_u64(duty_ns * rate, (pre_div + 1) * NSEC_PER_SEC); > >> + > >> + val = FIELD_PREP(IPQ_PWM_REG0_HI_DURATION, hi_dur) | > >> + FIELD_PREP(IPQ_PWM_REG0_PWM_DIV, pwm_div); > >> + ipq_pwm_reg_write(pwm, IPQ_PWM_REG0, val); > >> + > >> + val = FIELD_PREP(IPQ_PWM_REG1_PRE_DIV, pre_div); > >> + ipq_pwm_reg_write(pwm, IPQ_PWM_REG1, val); > >> + > >> + /* PWM enable toggle needs a separate write to REG1 */ > >> + val |= IPQ_PWM_REG1_UPDATE; > >> + if (enable) > >> + val |= IPQ_PWM_REG1_ENABLE; > >> + ipq_pwm_reg_write(pwm, IPQ_PWM_REG1, val); > >> +} > >> + > >> +static int ipq_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, > >> + const struct pwm_state *state) > >> +{ > >> + struct ipq_pwm_chip *ipq_chip = ipq_pwm_from_chip(chip); > >> + unsigned int pre_div, pwm_div, best_pre_div, best_pwm_div; > >> + unsigned long rate = clk_get_rate(ipq_chip->clk); > >> + u64 period_ns, duty_ns, period_rate; > >> + u64 min_diff; > >> + > >> + if (state->polarity != PWM_POLARITY_NORMAL) > >> + return -EINVAL; > >> + > >> + if (state->period < div64_u64(NSEC_PER_SEC, rate)) > >> + return -ERANGE; > > > > NSEC_PER_SEC / rate is the smallest period you can achieve, right? > > Consider rate = 33333 (Hz), then the minimal period is > > 30000.30000300003 ns. So you should refuse a request to configure > > state->period = 30000, but as div64_u64(1000000000, 33333) is 30000 you > > don't. > > > >> + period_ns = min(state->period, IPQ_PWM_MAX_PERIOD_NS); > >> + duty_ns = min(state->duty_cycle, period_ns); > >> + > >> + /* > >> + * period_ns is 1G or less. As long as rate is less than 16 GHz this > >> + * does not overflow. > > > > Well, rate cannot be bigger than 4294967295 because an unsigned long > > cannot hold a bigger value. > > On 64-bit systems __SIZEOF_LONG__ is 8, which can hold more than 2^32. Ah right, then I suggest to check that in code to make it more explicit than in a comment. > >> + */ > >> + period_rate = period_ns * rate; > >> + best_pre_div = IPQ_PWM_MAX_DIV; > >> + best_pwm_div = IPQ_PWM_MAX_DIV; > >> + /* Initial pre_div value such that pwm_div < IPQ_PWM_MAX_DIV */ > > Note this comment. <= ? > > >> + pre_div = div64_u64(period_rate, > >> + (u64)NSEC_PER_SEC * (IPQ_PWM_MAX_DIV + 1)); > > > > Hmmm, we want > > > > (pre_div + 1) * (pwm_div + 1) * NSEC_PER_SEC > > -------------------------------------------- <= period_ns > > rate > > > > , right? Resolving that for pre_div this gives: > > > > period_ns * rate > > pre_div <= ---------------------------- > > NSEC_PER_SEC * (pwm_div + 1) > > > > The term on the right hand side is maximal for pwm_div == 0 so the > > possible values for pre_div are > > > > 0 ... min(div64_u64(period_rate / NSEC_PER_SEC), IPQ_PWM_MAX_DIV) > > > > isn't it? > > I don't think so. pre_div == 0 will produce pwm_div larger than > IPQ_PWM_MAX_DIV for a large period_rate value. The initial pre_div here is the > smallest value that produces pwm_div within it limit. Ah, got your reasoning. If a pre_div is picked that is smaller than the value you calculate, a bigger pre_div results in a better approximation. What strikes me is that if you pick a smaller pre_div, you can still use pwm_div = IPQ_PWM_MAX_DIV which yields an allowed setting. So while your argument is right, I'd need a better comment to actually understand it. Something like: /* * We don't need to consider pre_div values smaller than * * period_rate * pre_div_min := ------------------------------------ * NSEC_PER_SEC * (IPQ_PWM_MAX_DIV + 1) * * because pre_div = pre_div_min results in a better * approximation. */ > > If so, your algorithm is wrong as you're iterating over > > > > div64_u64(period_rate, NSEC_PER_SEC * (IPQ_PWM_MAX_DIV + 1)) ... IPQ_PWM_MAX_DIV > > The loop stops when pre_div > pwm_div. That should be before pre_div == > IPQ_PWM_MAX_DIV because pwm_div <= IPQ_PWM_MAX_DIV. Should I put the pre_div > > pwm_div condition directly in the for statement? OK, moving the check isn't necessary. > > The task here is to calculate the biggest pwm_div for a given pre_div > > such that > > > > > > (pre_div + 1) * (pwm_div + 1) * NSEC_PER_SEC > > -------------------------------------------- <= period_ns > > rate > > > > right? > > > > This is equivalent to: > > > > period_ns * rate > > pre_div <= ---------------------------- - 1 > > (pre_div + 1) * NSEC_PER_SEC > > > > As pre_div is integer, rounding down should be fine?! > > I can't follow. With round down (as in v8) the result is always: > > NSEC_PER_SEC * (pre_div + 1) * (pwm_div + 1) <= period_rate Yes, that's the condition that a valid configuration should fulfill because then the configured period is never bigger than the requested period. > As a result, 'diff' calculation below will always produce diff <= 0. When > there is no diff == 0 result (bingo) we get IPQ_PWM_MAX_DIV in both best_ > values at the end of the loop. Looking again, your check is wrong. I think you need: diff = period_rate - NSEC_PER_SEC * (pre_div + 1) * (pwm_div + 1) . Given the calculations for pre_div and pwm_div this should never be negative and you should pick values that minimize diff. > Do we actually need diff > 0 in the condition below? > > >> + /* > >> + * pre_div and pwm_div values swap produces the same > >> + * result. This loop goes over all pre_div <= pwm_div > >> + * combinations. The rest are equivalent. > >> + */ > > > > I'd write: > > > > /* > > * Swapping values for pre_div and pwm_div produces the same > > * period length. So we can skip all settings with pre_div < > > * pwm_div which results in bigger constraints for selecting the > > * duty_cycle than with the two values swapped. > > */ > > I'll take your wording with inverted inequality sign. Right. Looking forward to your next iteration. Best regards Uwe
Hi Uwe, On Tue, Jan 25 2022, Uwe Kleine-König wrote: > On Tue, Jan 25, 2022 at 03:03:08PM +0200, Baruch Siach wrote: >> On Wed, Jan 19 2022, Uwe Kleine-König wrote: >> > The task here is to calculate the biggest pwm_div for a given pre_div >> > such that >> > >> > >> > (pre_div + 1) * (pwm_div + 1) * NSEC_PER_SEC >> > -------------------------------------------- <= period_ns >> > rate >> > >> > right? >> > >> > This is equivalent to: >> > >> > period_ns * rate >> > pre_div <= ---------------------------- - 1 >> > (pre_div + 1) * NSEC_PER_SEC >> > >> > As pre_div is integer, rounding down should be fine?! >> >> I can't follow. With round down (as in v8) the result is always: >> >> NSEC_PER_SEC * (pre_div + 1) * (pwm_div + 1) <= period_rate > > Yes, that's the condition that a valid configuration should fulfill > because then the configured period is never bigger than the requested > period. > >> As a result, 'diff' calculation below will always produce diff <= 0. When >> there is no diff == 0 result (bingo) we get IPQ_PWM_MAX_DIV in both best_ >> values at the end of the loop. > > Looking again, your check is wrong. I think you need: > > diff = period_rate - NSEC_PER_SEC * (pre_div + 1) * (pwm_div + 1) > > . Given the calculations for pre_div and pwm_div this should never be > negative and you should pick values that minimize diff. So, if I understand correctly, you suggest to leave round up as in v10, and invert the diff calculation. Is that correct? Thanks, baruch
Hello Baruch, On Tue, Jan 25, 2022 at 06:22:45PM +0200, Baruch Siach wrote: > On Tue, Jan 25 2022, Uwe Kleine-König wrote: > > On Tue, Jan 25, 2022 at 03:03:08PM +0200, Baruch Siach wrote: > >> On Wed, Jan 19 2022, Uwe Kleine-König wrote: > >> > The task here is to calculate the biggest pwm_div for a given pre_div > >> > such that > >> > > >> > > >> > (pre_div + 1) * (pwm_div + 1) * NSEC_PER_SEC > >> > -------------------------------------------- <= period_ns > >> > rate > >> > > >> > right? > >> > > >> > This is equivalent to: > >> > > >> > period_ns * rate > >> > pre_div <= ---------------------------- - 1 > >> > (pre_div + 1) * NSEC_PER_SEC > >> > > >> > As pre_div is integer, rounding down should be fine?! > >> > >> I can't follow. With round down (as in v8) the result is always: > >> > >> NSEC_PER_SEC * (pre_div + 1) * (pwm_div + 1) <= period_rate > > > > Yes, that's the condition that a valid configuration should fulfill > > because then the configured period is never bigger than the requested > > period. > > > >> As a result, 'diff' calculation below will always produce diff <= 0. When > >> there is no diff == 0 result (bingo) we get IPQ_PWM_MAX_DIV in both best_ > >> values at the end of the loop. > > > > Looking again, your check is wrong. I think you need: > > > > diff = period_rate - NSEC_PER_SEC * (pre_div + 1) * (pwm_div + 1) > > > > . Given the calculations for pre_div and pwm_div this should never be > > negative and you should pick values that minimize diff. > > So, if I understand correctly, you suggest to leave round up as in v10, > and invert the diff calculation. Is that correct? If you agree that this results in the intended setting and keeps dmesg clean even with PWM_DEBUG enabled: yes. Best regards Uwe
diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig index 21e3b05a5153..e39718137ecd 100644 --- a/drivers/pwm/Kconfig +++ b/drivers/pwm/Kconfig @@ -260,6 +260,18 @@ config PWM_INTEL_LGM To compile this driver as a module, choose M here: the module will be called pwm-intel-lgm. +config PWM_IPQ + tristate "IPQ PWM support" + depends on ARCH_QCOM || COMPILE_TEST + depends on HAVE_CLK && HAS_IOMEM + help + Generic PWM framework driver for IPQ PWM block which supports + 4 pwm channels. Each of the these channels can be configured + independent of each other. + + To compile this driver as a module, choose M here: the module + will be called pwm-ipq. + config PWM_IQS620A tristate "Azoteq IQS620A PWM support" depends on MFD_IQS62X || COMPILE_TEST diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile index 708840b7fba8..7402feae4b36 100644 --- a/drivers/pwm/Makefile +++ b/drivers/pwm/Makefile @@ -22,6 +22,7 @@ obj-$(CONFIG_PWM_IMX1) += pwm-imx1.o obj-$(CONFIG_PWM_IMX27) += pwm-imx27.o obj-$(CONFIG_PWM_IMX_TPM) += pwm-imx-tpm.o obj-$(CONFIG_PWM_INTEL_LGM) += pwm-intel-lgm.o +obj-$(CONFIG_PWM_IPQ) += pwm-ipq.o obj-$(CONFIG_PWM_IQS620A) += pwm-iqs620a.o obj-$(CONFIG_PWM_JZ4740) += pwm-jz4740.o obj-$(CONFIG_PWM_KEEMBAY) += pwm-keembay.o diff --git a/drivers/pwm/pwm-ipq.c b/drivers/pwm/pwm-ipq.c new file mode 100644 index 000000000000..3764010808f0 --- /dev/null +++ b/drivers/pwm/pwm-ipq.c @@ -0,0 +1,275 @@ +// SPDX-License-Identifier: BSD-3-Clause OR GPL-2.0 +/* + * Copyright (c) 2016-2017, 2020 The Linux Foundation. All rights reserved. + */ + +#include <linux/module.h> +#include <linux/platform_device.h> +#include <linux/pwm.h> +#include <linux/clk.h> +#include <linux/io.h> +#include <linux/of.h> +#include <linux/math64.h> +#include <linux/of_device.h> +#include <linux/bitfield.h> + +/* The frequency range supported is 1 Hz to clock rate */ +#define IPQ_PWM_MAX_PERIOD_NS ((u64)NSEC_PER_SEC) + +/* + * The max value specified for each field is based on the number of bits + * in the pwm control register for that field + */ +#define IPQ_PWM_MAX_DIV 0xFFFF + +/* + * Two 32-bit registers for each PWM: REG0, and REG1. + * Base offset for PWM #i is at 8 * #i. + */ +#define IPQ_PWM_REG0 0 /*PWM_DIV PWM_HI*/ +#define IPQ_PWM_REG0_PWM_DIV GENMASK(15, 0) +#define IPQ_PWM_REG0_HI_DURATION GENMASK(31, 16) + +#define IPQ_PWM_REG1 4 /*ENABLE UPDATE PWM_PRE_DIV*/ +#define IPQ_PWM_REG1_PRE_DIV GENMASK(15, 0) +/* + * Enable bit is set to enable output toggling in pwm device. + * Update bit is set to reflect the changed divider and high duration + * values in register. + */ +#define IPQ_PWM_REG1_UPDATE BIT(30) +#define IPQ_PWM_REG1_ENABLE BIT(31) + + +struct ipq_pwm_chip { + struct pwm_chip chip; + struct clk *clk; + void __iomem *mem; +}; + +static struct ipq_pwm_chip *ipq_pwm_from_chip(struct pwm_chip *chip) +{ + return container_of(chip, struct ipq_pwm_chip, chip); +} + +static unsigned int ipq_pwm_reg_read(struct pwm_device *pwm, unsigned int reg) +{ + struct ipq_pwm_chip *ipq_chip = ipq_pwm_from_chip(pwm->chip); + unsigned int off = 8 * pwm->hwpwm + reg; + + return readl(ipq_chip->mem + off); +} + +static void ipq_pwm_reg_write(struct pwm_device *pwm, unsigned int reg, + unsigned int val) +{ + struct ipq_pwm_chip *ipq_chip = ipq_pwm_from_chip(pwm->chip); + unsigned int off = 8 * pwm->hwpwm + reg; + + writel(val, ipq_chip->mem + off); +} + +static void config_div_and_duty(struct pwm_device *pwm, unsigned int pre_div, + unsigned int pwm_div, unsigned long rate, u64 duty_ns, + bool enable) +{ + unsigned long hi_dur; + unsigned long val = 0; + + /* + * high duration = pwm duty * (pwm div + 1) + * pwm duty = duty_ns / period_ns + */ + hi_dur = div64_u64(duty_ns * rate, (pre_div + 1) * NSEC_PER_SEC); + + val = FIELD_PREP(IPQ_PWM_REG0_HI_DURATION, hi_dur) | + FIELD_PREP(IPQ_PWM_REG0_PWM_DIV, pwm_div); + ipq_pwm_reg_write(pwm, IPQ_PWM_REG0, val); + + val = FIELD_PREP(IPQ_PWM_REG1_PRE_DIV, pre_div); + ipq_pwm_reg_write(pwm, IPQ_PWM_REG1, val); + + /* PWM enable toggle needs a separate write to REG1 */ + val |= IPQ_PWM_REG1_UPDATE; + if (enable) + val |= IPQ_PWM_REG1_ENABLE; + ipq_pwm_reg_write(pwm, IPQ_PWM_REG1, val); +} + +static int ipq_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm, + const struct pwm_state *state) +{ + struct ipq_pwm_chip *ipq_chip = ipq_pwm_from_chip(chip); + unsigned int pre_div, pwm_div, best_pre_div, best_pwm_div; + unsigned long rate = clk_get_rate(ipq_chip->clk); + u64 period_ns, duty_ns, period_rate; + u64 min_diff; + + if (state->polarity != PWM_POLARITY_NORMAL) + return -EINVAL; + + if (state->period < div64_u64(NSEC_PER_SEC, rate)) + return -ERANGE; + + period_ns = min(state->period, IPQ_PWM_MAX_PERIOD_NS); + duty_ns = min(state->duty_cycle, period_ns); + + /* + * period_ns is 1G or less. As long as rate is less than 16 GHz this + * does not overflow. + */ + period_rate = period_ns * rate; + best_pre_div = IPQ_PWM_MAX_DIV; + best_pwm_div = IPQ_PWM_MAX_DIV; + /* Initial pre_div value such that pwm_div < IPQ_PWM_MAX_DIV */ + pre_div = div64_u64(period_rate, + (u64)NSEC_PER_SEC * (IPQ_PWM_MAX_DIV + 1)); + min_diff = period_rate; + + for (; pre_div <= IPQ_PWM_MAX_DIV; pre_div++) { + long long diff; + + pwm_div = DIV64_U64_ROUND_UP(period_rate, + (u64)NSEC_PER_SEC * (pre_div + 1)); + /* pwm_div is unsigned; the check below catches underflow */ + pwm_div--; + + /* + * pre_div and pwm_div values swap produces the same + * result. This loop goes over all pre_div <= pwm_div + * combinations. The rest are equivalent. + */ + if (pre_div > pwm_div) + break; + + /* + * Make sure we can do 100% duty cycle where + * hi_dur == pwm_div + 1 + */ + if (pwm_div > IPQ_PWM_MAX_DIV - 1) + continue; + + diff = ((uint64_t)NSEC_PER_SEC * (pre_div + 1) * (pwm_div + 1)) + - period_rate; + + if (diff < 0) /* period larger than requested */ + continue; + if (diff == 0) { /* bingo */ + best_pre_div = pre_div; + best_pwm_div = pwm_div; + break; + } + if (diff < min_diff) { + min_diff = diff; + best_pre_div = pre_div; + best_pwm_div = pwm_div; + } + } + + /* config divider values for the closest possible frequency */ + config_div_and_duty(pwm, best_pre_div, best_pwm_div, + rate, duty_ns, state->enabled); + + return 0; +} + +static void ipq_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm, + struct pwm_state *state) +{ + struct ipq_pwm_chip *ipq_chip = ipq_pwm_from_chip(chip); + unsigned long rate = clk_get_rate(ipq_chip->clk); + unsigned int pre_div, pwm_div, hi_dur; + u64 effective_div, hi_div; + u32 reg0, reg1; + + reg0 = ipq_pwm_reg_read(pwm, IPQ_PWM_REG0); + reg1 = ipq_pwm_reg_read(pwm, IPQ_PWM_REG1); + + state->polarity = PWM_POLARITY_NORMAL; + state->enabled = reg1 & IPQ_PWM_REG1_ENABLE; + + pwm_div = FIELD_GET(IPQ_PWM_REG0_PWM_DIV, reg0); + hi_dur = FIELD_GET(IPQ_PWM_REG0_HI_DURATION, reg0); + pre_div = FIELD_GET(IPQ_PWM_REG1_PRE_DIV, reg1); + + /* No overflow here, both pre_div and pwm_div <= 0xffff */ + effective_div = (u64)(pre_div + 1) * (pwm_div + 1); + state->period = DIV64_U64_ROUND_UP(effective_div * NSEC_PER_SEC, rate); + + hi_div = hi_dur * (pre_div + 1); + state->duty_cycle = div64_u64(hi_div * NSEC_PER_SEC, rate); +} + +static const struct pwm_ops ipq_pwm_ops = { + .apply = ipq_pwm_apply, + .get_state = ipq_pwm_get_state, + .owner = THIS_MODULE, +}; + +static int ipq_pwm_probe(struct platform_device *pdev) +{ + struct ipq_pwm_chip *pwm; + struct device *dev = &pdev->dev; + int ret; + + pwm = devm_kzalloc(dev, sizeof(*pwm), GFP_KERNEL); + if (!pwm) + return -ENOMEM; + + platform_set_drvdata(pdev, pwm); + + pwm->mem = devm_platform_ioremap_resource(pdev, 0); + if (IS_ERR(pwm->mem)) + return dev_err_probe(dev, PTR_ERR(pwm->mem), + "regs map failed"); + + pwm->clk = devm_clk_get(dev, NULL); + if (IS_ERR(pwm->clk)) + return dev_err_probe(dev, PTR_ERR(pwm->clk), + "failed to get clock"); + + ret = clk_prepare_enable(pwm->clk); + if (ret) + return dev_err_probe(dev, ret, "clock enable failed"); + + pwm->chip.dev = dev; + pwm->chip.ops = &ipq_pwm_ops; + pwm->chip.npwm = 4; + + ret = pwmchip_add(&pwm->chip); + if (ret < 0) { + dev_err_probe(dev, ret, "pwmchip_add() failed\n"); + clk_disable_unprepare(pwm->clk); + } + + return ret; +} + +static int ipq_pwm_remove(struct platform_device *pdev) +{ + struct ipq_pwm_chip *pwm = platform_get_drvdata(pdev); + + pwmchip_remove(&pwm->chip); + clk_disable_unprepare(pwm->clk); + + return 0; +} + +static const struct of_device_id pwm_ipq_dt_match[] = { + { .compatible = "qcom,ipq6018-pwm", }, + {} +}; +MODULE_DEVICE_TABLE(of, pwm_ipq_dt_match); + +static struct platform_driver ipq_pwm_driver = { + .driver = { + .name = "ipq-pwm", + .of_match_table = pwm_ipq_dt_match, + }, + .probe = ipq_pwm_probe, + .remove = ipq_pwm_remove, +}; + +module_platform_driver(ipq_pwm_driver); + +MODULE_LICENSE("Dual BSD/GPL");