diff mbox series

[v6,2/2] pwm: Add Aspeed ast2600 PWM support

Message ID 20210518005517.9036-3-billy_tsai@aspeedtech.com
State Superseded, archived
Headers show
Series Support pwm driver for aspeed ast26xx | expand

Commit Message

Billy Tsai May 18, 2021, 12:55 a.m. UTC
This patch add the support of PWM controller which can be found at aspeed
ast2600 soc. The pwm supoorts up to 16 channels and it's part function
of multi-function device "pwm-tach controller".

Signed-off-by: Billy Tsai <billy_tsai@aspeedtech.com>
---
 drivers/pwm/Kconfig         |   9 +
 drivers/pwm/Makefile        |   1 +
 drivers/pwm/pwm-aspeed-g6.c | 351 ++++++++++++++++++++++++++++++++++++
 3 files changed, 361 insertions(+)
 create mode 100644 drivers/pwm/pwm-aspeed-g6.c

Comments

Uwe Kleine-König May 22, 2021, 4:07 p.m. UTC | #1
Hello,

On Tue, May 18, 2021 at 08:55:17AM +0800, Billy Tsai wrote:
> This patch add the support of PWM controller which can be found at aspeed
> ast2600 soc. The pwm supoorts up to 16 channels and it's part function
> of multi-function device "pwm-tach controller".
> 
> Signed-off-by: Billy Tsai <billy_tsai@aspeedtech.com>
> ---
>  drivers/pwm/Kconfig         |   9 +
>  drivers/pwm/Makefile        |   1 +
>  drivers/pwm/pwm-aspeed-g6.c | 351 ++++++++++++++++++++++++++++++++++++
>  3 files changed, 361 insertions(+)
>  create mode 100644 drivers/pwm/pwm-aspeed-g6.c
> 
> diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
> index 63be5362fd3a..3b2d4cf024a6 100644
> --- a/drivers/pwm/Kconfig
> +++ b/drivers/pwm/Kconfig
> @@ -51,6 +51,15 @@ config PWM_AB8500
>  	  To compile this driver as a module, choose M here: the module
>  	  will be called pwm-ab8500.
>  
> +config PWM_ASPEED_G6
> +	tristate "ASPEEDG6 PWM support"
> +	depends on ARCH_ASPEED || COMPILE_TEST
> +	help
> +	  Generic PWM framework driver for ASPEED G6 SoC.
> +
> +	  To compile this driver as a module, choose M here: the module
> +	  will be called pwm-aspeed-g6.
> +
>  config PWM_ATMEL
>  	tristate "Atmel PWM support"
>  	depends on OF
> diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
> index cbdcd55d69ee..29d22d806e68 100644
> --- a/drivers/pwm/Makefile
> +++ b/drivers/pwm/Makefile
> @@ -2,6 +2,7 @@
>  obj-$(CONFIG_PWM)		+= core.o
>  obj-$(CONFIG_PWM_SYSFS)		+= sysfs.o
>  obj-$(CONFIG_PWM_AB8500)	+= pwm-ab8500.o
> +obj-$(CONFIG_PWM_ASPEED_G6)	+= pwm-aspeed-g6.o
>  obj-$(CONFIG_PWM_ATMEL)		+= pwm-atmel.o
>  obj-$(CONFIG_PWM_ATMEL_HLCDC_PWM)	+= pwm-atmel-hlcdc.o
>  obj-$(CONFIG_PWM_ATMEL_TCB)	+= pwm-atmel-tcb.o
> diff --git a/drivers/pwm/pwm-aspeed-g6.c b/drivers/pwm/pwm-aspeed-g6.c
> new file mode 100644
> index 000000000000..a80211eb4877
> --- /dev/null
> +++ b/drivers/pwm/pwm-aspeed-g6.c
> @@ -0,0 +1,351 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Copyright (C) 2021 ASPEED Technology Inc.
> + *
> + * PWM controller driver for Aspeed ast26xx SoCs.
> + * This drivers doesn't support earlier version of the IP.
> + *
> + * The formula of pwm frequency:
> + * PWM frequency = CLK Source / ((DIV_L + 1) * BIT(DIV_H) * (PERIOD + 1))
> + *
> + * The software driver fixes the period to 255, which causes the high-frequency
> + * precision of the PWM to be coarse, in exchange for the fineness of the duty cycle.
> + *
> + * Register usage:
> + * PIN_ENABLE: When it is unset the pwm controller will always output low to the extern.
> + * Use to determine whether the PWM channel is enabled or disabled
> + * CLK_ENABLE: When it is unset the pwm controller will reset the duty counter to 0 and
> + * output low to the PIN_ENABLE mux after that the driver can still change the pwm period
> + * and duty and the value will apply when CLK_ENABLE be set again.
> + * Use to determin whether duty_cycle bigger than 0.
> + * PWM_ASPEED_CTRL_INVERSE: When it is toggled the output value will inverse immediately.
> + * PWM_ASPEED_DUTY_CYCLE_FALLING_POINT/PWM_ASPEED_DUTY_CYCLE_RISING_POINT: When these two
> + * values are equal it means the duty cycle = 100%.
> + *
> + * Limitations:
> + * - When changing both duty cycle and period, we cannot prevent in
> + *   software that the output might produce a period with mixed
> + *   settings.
> + *
> + * Improvements:
> + * - When changing the duty cycle or period, our pwm controller will not
> + *   generate the glitch, the configure will change at next cycle of pwm.
> + *   This improvement can disable/enable through PWM_ASPEED_CTRL_DUTY_SYNC_DISABLE.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/errno.h>
> +#include <linux/delay.h>
> +#include <linux/io.h>
> +#include <linux/kernel.h>
> +#include <linux/mfd/syscon.h>
> +#include <linux/module.h>
> +#include <linux/of_platform.h>
> +#include <linux/of_device.h>
> +#include <linux/platform_device.h>
> +#include <linux/sysfs.h>
> +#include <linux/reset.h>
> +#include <linux/regmap.h>
> +#include <linux/bitfield.h>
> +#include <linux/slab.h>
> +#include <linux/pwm.h>
> +#include <linux/math64.h>
> +
> +/* The channel number of Aspeed pwm controller */
> +#define PWM_ASPEED_NR_PWMS 16
> +
> +/* PWM Control Register */
> +#define PWM_ASPEED_CTRL_CH(ch) (((ch)*0x10) + 0x00)
> +#define PWM_ASPEED_CTRL_LOAD_SEL_RISING_AS_WDT BIT(19)
> +#define PWM_ASPEED_CTRL_DUTY_LOAD_AS_WDT_ENABLE BIT(18)
> +#define PWM_ASPEED_CTRL_DUTY_SYNC_DISABLE BIT(17)
> +#define PWM_ASPEED_CTRL_CLK_ENABLE BIT(16)
> +#define PWM_ASPEED_CTRL_LEVEL_OUTPUT BIT(15)
> +#define PWM_ASPEED_CTRL_INVERSE BIT(14)
> +#define PWM_ASPEED_CTRL_OPEN_DRAIN_ENABLE BIT(13)
> +#define PWM_ASPEED_CTRL_PIN_ENABLE BIT(12)
> +#define PWM_ASPEED_CTRL_CLK_DIV_H GENMASK(11, 8)
> +#define PWM_ASPEED_CTRL_CLK_DIV_L GENMASK(7, 0)
> +
> +/* PWM Duty Cycle Register */
> +#define PWM_ASPEED_DUTY_CYCLE_CH(ch) (((ch)*0x10) + 0x04)
> +#define PWM_ASPEED_DUTY_CYCLE_PERIOD GENMASK(31, 24)
> +#define PWM_ASPEED_DUTY_CYCLE_POINT_AS_WDT GENMASK(23, 16)
> +#define PWM_ASPEED_DUTY_CYCLE_FALLING_POINT GENMASK(15, 8)
> +#define PWM_ASPEED_DUTY_CYCLE_RISING_POINT GENMASK(7, 0)
> +
> +/* PWM fixed value */
> +#define PWM_ASPEED_FIXED_PERIOD FIELD_MAX(PWM_ASPEED_DUTY_CYCLE_PERIOD)
> +
> +struct aspeed_pwm_data {
> +	struct pwm_chip chip;
> +	struct clk *clk;
> +	struct regmap *regmap;
> +	struct reset_control *reset;
> +};
> +
> +static inline struct aspeed_pwm_data *
> +aspeed_pwm_chip_to_data(struct pwm_chip *c)
> +{
> +	return container_of(c, struct aspeed_pwm_data, chip);
> +}
> +
> +static u64 aspeed_pwm_get_period(struct pwm_chip *chip, struct pwm_device *pwm)
> +{
> +	struct aspeed_pwm_data *priv = aspeed_pwm_chip_to_data(chip);
> +	unsigned long rate;
> +	u32 index = pwm->hwpwm;
> +	u32 val;
> +	u64 period, div_h, div_l, clk_period;
> +
> +	rate = clk_get_rate(priv->clk);
> +	regmap_read(priv->regmap, PWM_ASPEED_CTRL_CH(index), &val);
> +	div_h = FIELD_GET(PWM_ASPEED_CTRL_CLK_DIV_H, val);
> +	div_l = FIELD_GET(PWM_ASPEED_CTRL_CLK_DIV_L, val);
> +	regmap_read(priv->regmap, PWM_ASPEED_DUTY_CYCLE_CH(index), &val);
> +	clk_period = FIELD_GET(PWM_ASPEED_DUTY_CYCLE_PERIOD, val);
> +	period = (NSEC_PER_SEC * BIT(div_h) * (div_l + 1) * (clk_period + 1));

The outer pair of parenthesis on the RHS isn't necessary. The maximal
value that period can have here is:

	1000000000 * 2**15 * 256 * 256

This fits into an u64, but as all but the last factor are 32 bit values
you might get an overflow here.

> +	period = DIV_ROUND_UP_ULL(period, rate);
> +
> +	return period;
> +}
> +
> +static int aspeed_pwm_set_period(struct pwm_chip *chip, struct pwm_device *pwm,
> +				 const struct pwm_state *state)
> +{
> +	struct device *dev = chip->dev;
> +	struct aspeed_pwm_data *priv = aspeed_pwm_chip_to_data(chip);
> +	unsigned long rate;
> +	u64 div_h, div_l, divisor;
> +	u32 index = pwm->hwpwm;
> +
> +	rate = clk_get_rate(priv->clk);
> +	/*
> +	 * Pick the smallest value for div_h so that div_l can be the biggest
> +	 * which results in a finer resolution near the target period value.
> +	 */
> +	divisor = (u64)NSEC_PER_SEC * (PWM_ASPEED_FIXED_PERIOD + 1) *
> +		  (FIELD_MAX(PWM_ASPEED_CTRL_CLK_DIV_L) + 1);
> +	div_h = order_base_2(div64_u64(rate * state->period, divisor));
> +	if (div_h > 0xf)
> +		div_h = 0xf;
> +
> +	divisor = ((u64)NSEC_PER_SEC * (PWM_ASPEED_FIXED_PERIOD + 1)) << div_h;
> +	div_l = div64_u64(rate * state->period, divisor);
> +
> +	if (div_l == 0)
> +		return -ERANGE;
> +
> +	div_l -= 1;
> +
> +	if (div_l > 255)
> +		div_l = 255;
> +
> +	dev_dbg(dev, "clk source: %ld div_h %lld, div_l : %lld\n", rate, div_h,
> +		div_l);
> +
> +	regmap_update_bits(
> +		priv->regmap, PWM_ASPEED_CTRL_CH(index),
> +		(PWM_ASPEED_CTRL_CLK_DIV_H | PWM_ASPEED_CTRL_CLK_DIV_L),
> +		FIELD_PREP(PWM_ASPEED_CTRL_CLK_DIV_H, div_h) |
> +			FIELD_PREP(PWM_ASPEED_CTRL_CLK_DIV_L, div_l));
> +	return 0;
> +}
> +
> +static void aspeed_pwm_set_duty(struct pwm_chip *chip, struct pwm_device *pwm,
> +				const struct pwm_state *state)
> +{
> +	struct device *dev = chip->dev;
> +	struct aspeed_pwm_data *priv = aspeed_pwm_chip_to_data(chip);
> +	u32 duty_pt;
> +	u32 index = pwm->hwpwm;
> +	u64 cur_period;
> +
> +	cur_period = aspeed_pwm_get_period(chip, pwm);
> +	duty_pt = DIV_ROUND_DOWN_ULL(
> +		state->duty_cycle * (PWM_ASPEED_FIXED_PERIOD + 1), cur_period);
> +	dev_dbg(dev, "cur_period = %lld, duty_cycle = %lld, duty_pt = %d\n",
> +		cur_period, state->duty_cycle, duty_pt);
> +	if (duty_pt == 0) {
> +		regmap_update_bits(priv->regmap, PWM_ASPEED_CTRL_CH(index),
> +				   PWM_ASPEED_CTRL_CLK_ENABLE, 0);
> +	} else {
> +		if (duty_pt >= (PWM_ASPEED_FIXED_PERIOD + 1))
> +			duty_pt = 0;
> +		regmap_update_bits(
> +			priv->regmap, PWM_ASPEED_DUTY_CYCLE_CH(index),
> +			PWM_ASPEED_DUTY_CYCLE_FALLING_POINT,
> +			FIELD_PREP(PWM_ASPEED_DUTY_CYCLE_FALLING_POINT,
> +				   duty_pt));
> +		regmap_update_bits(priv->regmap, PWM_ASPEED_CTRL_CH(index),
> +				   PWM_ASPEED_CTRL_CLK_ENABLE,
> +				   PWM_ASPEED_CTRL_CLK_ENABLE);
> +	}
> +}
> +
> +static void aspeed_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
> +				 struct pwm_state *state)
> +{
> +	struct device *dev = chip->dev;
> +	struct aspeed_pwm_data *priv = aspeed_pwm_chip_to_data(chip);
> +	u32 index = pwm->hwpwm;
> +	bool polarity, ch_en, clk_en;
> +	u32 duty_pt, val;
> +
> +	regmap_read(priv->regmap, PWM_ASPEED_CTRL_CH(index), &val);
> +	polarity = FIELD_GET(PWM_ASPEED_CTRL_INVERSE, val);
> +	ch_en = FIELD_GET(PWM_ASPEED_CTRL_PIN_ENABLE, val);
> +	clk_en = FIELD_GET(PWM_ASPEED_CTRL_CLK_ENABLE, val);
> +	regmap_read(priv->regmap, PWM_ASPEED_DUTY_CYCLE_CH(index), &val);
> +	duty_pt = FIELD_GET(PWM_ASPEED_DUTY_CYCLE_FALLING_POINT, val);
> +
> +	state->period = aspeed_pwm_get_period(chip, pwm);
> +	if (clk_en && duty_pt)
> +		state->duty_cycle = DIV_ROUND_UP_ULL(
> +			state->period * duty_pt, PWM_ASPEED_FIXED_PERIOD + 1);
> +	else
> +		state->duty_cycle = clk_en ? state->period : 0;
> +	state->polarity = polarity;
> +	state->enabled = ch_en;
> +	dev_dbg(dev, "get period: %lldns, duty_cycle: %lldns", state->period,
> +		state->duty_cycle);
> +}
> +
> +static int aspeed_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
> +			    const struct pwm_state *state)
> +{
> +	struct device *dev = chip->dev;
> +	struct aspeed_pwm_data *priv = aspeed_pwm_chip_to_data(chip);
> +	u32 index = pwm->hwpwm;
> +	int ret;
> +
> +	dev_dbg(dev, "apply period: %lldns, duty_cycle: %lldns", state->period,
> +		state->duty_cycle);
> +
> +	regmap_update_bits(priv->regmap, PWM_ASPEED_CTRL_CH(index),
> +			   PWM_ASPEED_CTRL_PIN_ENABLE,
> +			   state->enabled ? PWM_ASPEED_CTRL_PIN_ENABLE : 0);
> +	/*
> +	 * Fixed the period to the max value and rising point to 0
> +	 * for high resolution and simplify frequency calculation.
> +	 */
> +	regmap_update_bits(priv->regmap, PWM_ASPEED_DUTY_CYCLE_CH(index),
> +			   (PWM_ASPEED_DUTY_CYCLE_PERIOD |
> +			    PWM_ASPEED_DUTY_CYCLE_RISING_POINT),
> +			   FIELD_PREP(PWM_ASPEED_DUTY_CYCLE_PERIOD,
> +				      PWM_ASPEED_FIXED_PERIOD));
> +
> +	ret = aspeed_pwm_set_period(chip, pwm, state);
> +	if (ret)
> +		return ret;
> +	aspeed_pwm_set_duty(chip, pwm, state);

aspeed_pwm_set_duty calls aspeed_pwm_get_period() which is a bit
ineffective after just having set the period.

> +	regmap_update_bits(priv->regmap, PWM_ASPEED_CTRL_CH(index),
> +			   PWM_ASPEED_CTRL_INVERSE,
> +			   FIELD_PREP(PWM_ASPEED_CTRL_INVERSE,
> +				      state->polarity));
> +	return 0;
> +}

Best regards
Uwe
Billy Tsai May 24, 2021, 1:56 a.m. UTC | #2
Hi,

On 2021/5/23, 12:07 AM,Uwe Kleine-Königwrote:

    Hello,

    On Tue, May 18, 2021 at 08:55:17AM +0800, Billy Tsai wrote:
    >   > +static u64 aspeed_pwm_get_period(struct pwm_chip *chip, struct pwm_device *pwm)
    >   > +{
    >   > +	struct aspeed_pwm_data *priv = aspeed_pwm_chip_to_data(chip);
    >   > +	unsigned long rate;
    >   > +	u32 index = pwm->hwpwm;
    >   > +	u32 val;
    >   > +	u64 period, div_h, div_l, clk_period;
    >   > +
    >   > +	rate = clk_get_rate(priv->clk);
    >   > +	regmap_read(priv->regmap, PWM_ASPEED_CTRL_CH(index), &val);
    >   > +	div_h = FIELD_GET(PWM_ASPEED_CTRL_CLK_DIV_H, val);
    >   > +	div_l = FIELD_GET(PWM_ASPEED_CTRL_CLK_DIV_L, val);
    >   > +	regmap_read(priv->regmap, PWM_ASPEED_DUTY_CYCLE_CH(index), &val);
    >   > +	clk_period = FIELD_GET(PWM_ASPEED_DUTY_CYCLE_PERIOD, val);
    >   > +	period = (NSEC_PER_SEC * BIT(div_h) * (div_l + 1) * (clk_period + 1));

    > The outer pair of parenthesis on the RHS isn't necessary. The maximal
    > value that period can have here is:

    >	1000000000 * 2**15 * 256 * 256

    > This fits into an u64, but as all but the last factor are 32 bit values
    > you might get an overflow here.

I don’t know in which case the value will overflow, when my parameter types are all u64.
Can you tell me what is "the last factor"?

    >   > +static int aspeed_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
    >   > +			    const struct pwm_state *state)
    >   > +{
    >   > +	struct device *dev = chip->dev;
    >   > +	struct aspeed_pwm_data *priv = aspeed_pwm_chip_to_data(chip);
    >   > +	u32 index = pwm->hwpwm;
    >   > +	int ret;
    >   > +
    >   > +	dev_dbg(dev, "apply period: %lldns, duty_cycle: %lldns", state->period,
    >   > +		state->duty_cycle);
    >   > +
    >   > +	regmap_update_bits(priv->regmap, PWM_ASPEED_CTRL_CH(index),
    >   > +			   PWM_ASPEED_CTRL_PIN_ENABLE,
    >   > +			   state->enabled ? PWM_ASPEED_CTRL_PIN_ENABLE : 0);
    >   > +	/*
    >   > +	 * Fixed the period to the max value and rising point to 0
    >   > +	 * for high resolution and simplify frequency calculation.
    >   > +	 */
    >   > +	regmap_update_bits(priv->regmap, PWM_ASPEED_DUTY_CYCLE_CH(index),
    >   > +			   (PWM_ASPEED_DUTY_CYCLE_PERIOD |
    >   > +			    PWM_ASPEED_DUTY_CYCLE_RISING_POINT),
    >   > +			   FIELD_PREP(PWM_ASPEED_DUTY_CYCLE_PERIOD,
    >   > +				      PWM_ASPEED_FIXED_PERIOD));
    >   > +
    >   > +	ret = aspeed_pwm_set_period(chip, pwm, state);
    >   > +	if (ret)
    >   > +		return ret;
    >   > +	aspeed_pwm_set_duty(chip, pwm, state);

    > aspeed_pwm_set_duty calls aspeed_pwm_get_period() which is a bit
    > ineffective after just having set the period.

When I call aspeed_pwm_set_period it doesn't mean the period is equal to what I set (It may
lose some precision Ex: When I set the period 40000ns, the actual period I set is 39680ns) and
I didn't get this information when I call aspeed_pwm_set_period. Thus, I need to get the actual
period first before set duty.
Uwe Kleine-König May 24, 2021, 11:02 a.m. UTC | #3
Hi Billy,

On Mon, May 24, 2021 at 01:56:19AM +0000, Billy Tsai wrote:
> On 2021/5/23, 12:07 AM,Uwe Kleine-Königwrote:
>     On Tue, May 18, 2021 at 08:55:17AM +0800, Billy Tsai wrote:
>     >   > +static u64 aspeed_pwm_get_period(struct pwm_chip *chip, struct pwm_device *pwm)
>     >   > +{
>     >   > +	struct aspeed_pwm_data *priv = aspeed_pwm_chip_to_data(chip);
>     >   > +	unsigned long rate;
>     >   > +	u32 index = pwm->hwpwm;
>     >   > +	u32 val;
>     >   > +	u64 period, div_h, div_l, clk_period;
>     >   > +
>     >   > +	rate = clk_get_rate(priv->clk);
>     >   > +	regmap_read(priv->regmap, PWM_ASPEED_CTRL_CH(index), &val);
>     >   > +	div_h = FIELD_GET(PWM_ASPEED_CTRL_CLK_DIV_H, val);
>     >   > +	div_l = FIELD_GET(PWM_ASPEED_CTRL_CLK_DIV_L, val);
>     >   > +	regmap_read(priv->regmap, PWM_ASPEED_DUTY_CYCLE_CH(index), &val);
>     >   > +	clk_period = FIELD_GET(PWM_ASPEED_DUTY_CYCLE_PERIOD, val);
>     >   > +	period = (NSEC_PER_SEC * BIT(div_h) * (div_l + 1) * (clk_period + 1));
> 
>     > The outer pair of parenthesis on the RHS isn't necessary. The maximal
>     > value that period can have here is:
> 
>     >	1000000000 * 2**15 * 256 * 256
> 
>     > This fits into an u64, but as all but the last factor are 32 bit values
>     > you might get an overflow here.
> 
> I don’t know in which case the value will overflow, when my parameter types are all u64.
> Can you tell me what is "the last factor"?

Ah, I missed that div_l is u64. NSEC_PER_SEC and BIT(div_h) are both
long quantities only and 1000000000 * 2**15 might overflow that.

>     >   > +static int aspeed_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
>     >   > +			    const struct pwm_state *state)
>     >   > +{
>     >   > +	struct device *dev = chip->dev;
>     >   > +	struct aspeed_pwm_data *priv = aspeed_pwm_chip_to_data(chip);
>     >   > +	u32 index = pwm->hwpwm;
>     >   > +	int ret;
>     >   > +
>     >   > +	dev_dbg(dev, "apply period: %lldns, duty_cycle: %lldns", state->period,
>     >   > +		state->duty_cycle);
>     >   > +
>     >   > +	regmap_update_bits(priv->regmap, PWM_ASPEED_CTRL_CH(index),
>     >   > +			   PWM_ASPEED_CTRL_PIN_ENABLE,
>     >   > +			   state->enabled ? PWM_ASPEED_CTRL_PIN_ENABLE : 0);
>     >   > +	/*
>     >   > +	 * Fixed the period to the max value and rising point to 0
>     >   > +	 * for high resolution and simplify frequency calculation.
>     >   > +	 */
>     >   > +	regmap_update_bits(priv->regmap, PWM_ASPEED_DUTY_CYCLE_CH(index),
>     >   > +			   (PWM_ASPEED_DUTY_CYCLE_PERIOD |
>     >   > +			    PWM_ASPEED_DUTY_CYCLE_RISING_POINT),
>     >   > +			   FIELD_PREP(PWM_ASPEED_DUTY_CYCLE_PERIOD,
>     >   > +				      PWM_ASPEED_FIXED_PERIOD));
>     >   > +
>     >   > +	ret = aspeed_pwm_set_period(chip, pwm, state);
>     >   > +	if (ret)
>     >   > +		return ret;
>     >   > +	aspeed_pwm_set_duty(chip, pwm, state);
> 
>     > aspeed_pwm_set_duty calls aspeed_pwm_get_period() which is a bit
>     > ineffective after just having set the period.
> 
> When I call aspeed_pwm_set_period it doesn't mean the period is equal to what I set (It may
> lose some precision Ex: When I set the period 40000ns, the actual period I set is 39680ns) and
> I didn't get this information when I call aspeed_pwm_set_period. Thus, I need to get the actual
> period first before set duty.

I'm aware it might lose precision. But calling aspeed_pwm_get_period()
determines the setting from reading registers, if you reuse all
information available in aspeed_pwm_set_period() this is cheaper. Also
it might be beneficial to first compute all necessary register values
and then write them in quick sequence to keep the window for glitches
small. Given that aspeed_pwm_set_period and aspeed_pwm_set_duty both
have only a single caller, doing both in a single function might be an
idea.

Best regards
Uwe
diff mbox series

Patch

diff --git a/drivers/pwm/Kconfig b/drivers/pwm/Kconfig
index 63be5362fd3a..3b2d4cf024a6 100644
--- a/drivers/pwm/Kconfig
+++ b/drivers/pwm/Kconfig
@@ -51,6 +51,15 @@  config PWM_AB8500
 	  To compile this driver as a module, choose M here: the module
 	  will be called pwm-ab8500.
 
+config PWM_ASPEED_G6
+	tristate "ASPEEDG6 PWM support"
+	depends on ARCH_ASPEED || COMPILE_TEST
+	help
+	  Generic PWM framework driver for ASPEED G6 SoC.
+
+	  To compile this driver as a module, choose M here: the module
+	  will be called pwm-aspeed-g6.
+
 config PWM_ATMEL
 	tristate "Atmel PWM support"
 	depends on OF
diff --git a/drivers/pwm/Makefile b/drivers/pwm/Makefile
index cbdcd55d69ee..29d22d806e68 100644
--- a/drivers/pwm/Makefile
+++ b/drivers/pwm/Makefile
@@ -2,6 +2,7 @@ 
 obj-$(CONFIG_PWM)		+= core.o
 obj-$(CONFIG_PWM_SYSFS)		+= sysfs.o
 obj-$(CONFIG_PWM_AB8500)	+= pwm-ab8500.o
+obj-$(CONFIG_PWM_ASPEED_G6)	+= pwm-aspeed-g6.o
 obj-$(CONFIG_PWM_ATMEL)		+= pwm-atmel.o
 obj-$(CONFIG_PWM_ATMEL_HLCDC_PWM)	+= pwm-atmel-hlcdc.o
 obj-$(CONFIG_PWM_ATMEL_TCB)	+= pwm-atmel-tcb.o
diff --git a/drivers/pwm/pwm-aspeed-g6.c b/drivers/pwm/pwm-aspeed-g6.c
new file mode 100644
index 000000000000..a80211eb4877
--- /dev/null
+++ b/drivers/pwm/pwm-aspeed-g6.c
@@ -0,0 +1,351 @@ 
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2021 ASPEED Technology Inc.
+ *
+ * PWM controller driver for Aspeed ast26xx SoCs.
+ * This drivers doesn't support earlier version of the IP.
+ *
+ * The formula of pwm frequency:
+ * PWM frequency = CLK Source / ((DIV_L + 1) * BIT(DIV_H) * (PERIOD + 1))
+ *
+ * The software driver fixes the period to 255, which causes the high-frequency
+ * precision of the PWM to be coarse, in exchange for the fineness of the duty cycle.
+ *
+ * Register usage:
+ * PIN_ENABLE: When it is unset the pwm controller will always output low to the extern.
+ * Use to determine whether the PWM channel is enabled or disabled
+ * CLK_ENABLE: When it is unset the pwm controller will reset the duty counter to 0 and
+ * output low to the PIN_ENABLE mux after that the driver can still change the pwm period
+ * and duty and the value will apply when CLK_ENABLE be set again.
+ * Use to determin whether duty_cycle bigger than 0.
+ * PWM_ASPEED_CTRL_INVERSE: When it is toggled the output value will inverse immediately.
+ * PWM_ASPEED_DUTY_CYCLE_FALLING_POINT/PWM_ASPEED_DUTY_CYCLE_RISING_POINT: When these two
+ * values are equal it means the duty cycle = 100%.
+ *
+ * Limitations:
+ * - When changing both duty cycle and period, we cannot prevent in
+ *   software that the output might produce a period with mixed
+ *   settings.
+ *
+ * Improvements:
+ * - When changing the duty cycle or period, our pwm controller will not
+ *   generate the glitch, the configure will change at next cycle of pwm.
+ *   This improvement can disable/enable through PWM_ASPEED_CTRL_DUTY_SYNC_DISABLE.
+ */
+
+#include <linux/clk.h>
+#include <linux/errno.h>
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of_platform.h>
+#include <linux/of_device.h>
+#include <linux/platform_device.h>
+#include <linux/sysfs.h>
+#include <linux/reset.h>
+#include <linux/regmap.h>
+#include <linux/bitfield.h>
+#include <linux/slab.h>
+#include <linux/pwm.h>
+#include <linux/math64.h>
+
+/* The channel number of Aspeed pwm controller */
+#define PWM_ASPEED_NR_PWMS 16
+
+/* PWM Control Register */
+#define PWM_ASPEED_CTRL_CH(ch) (((ch)*0x10) + 0x00)
+#define PWM_ASPEED_CTRL_LOAD_SEL_RISING_AS_WDT BIT(19)
+#define PWM_ASPEED_CTRL_DUTY_LOAD_AS_WDT_ENABLE BIT(18)
+#define PWM_ASPEED_CTRL_DUTY_SYNC_DISABLE BIT(17)
+#define PWM_ASPEED_CTRL_CLK_ENABLE BIT(16)
+#define PWM_ASPEED_CTRL_LEVEL_OUTPUT BIT(15)
+#define PWM_ASPEED_CTRL_INVERSE BIT(14)
+#define PWM_ASPEED_CTRL_OPEN_DRAIN_ENABLE BIT(13)
+#define PWM_ASPEED_CTRL_PIN_ENABLE BIT(12)
+#define PWM_ASPEED_CTRL_CLK_DIV_H GENMASK(11, 8)
+#define PWM_ASPEED_CTRL_CLK_DIV_L GENMASK(7, 0)
+
+/* PWM Duty Cycle Register */
+#define PWM_ASPEED_DUTY_CYCLE_CH(ch) (((ch)*0x10) + 0x04)
+#define PWM_ASPEED_DUTY_CYCLE_PERIOD GENMASK(31, 24)
+#define PWM_ASPEED_DUTY_CYCLE_POINT_AS_WDT GENMASK(23, 16)
+#define PWM_ASPEED_DUTY_CYCLE_FALLING_POINT GENMASK(15, 8)
+#define PWM_ASPEED_DUTY_CYCLE_RISING_POINT GENMASK(7, 0)
+
+/* PWM fixed value */
+#define PWM_ASPEED_FIXED_PERIOD FIELD_MAX(PWM_ASPEED_DUTY_CYCLE_PERIOD)
+
+struct aspeed_pwm_data {
+	struct pwm_chip chip;
+	struct clk *clk;
+	struct regmap *regmap;
+	struct reset_control *reset;
+};
+
+static inline struct aspeed_pwm_data *
+aspeed_pwm_chip_to_data(struct pwm_chip *c)
+{
+	return container_of(c, struct aspeed_pwm_data, chip);
+}
+
+static u64 aspeed_pwm_get_period(struct pwm_chip *chip, struct pwm_device *pwm)
+{
+	struct aspeed_pwm_data *priv = aspeed_pwm_chip_to_data(chip);
+	unsigned long rate;
+	u32 index = pwm->hwpwm;
+	u32 val;
+	u64 period, div_h, div_l, clk_period;
+
+	rate = clk_get_rate(priv->clk);
+	regmap_read(priv->regmap, PWM_ASPEED_CTRL_CH(index), &val);
+	div_h = FIELD_GET(PWM_ASPEED_CTRL_CLK_DIV_H, val);
+	div_l = FIELD_GET(PWM_ASPEED_CTRL_CLK_DIV_L, val);
+	regmap_read(priv->regmap, PWM_ASPEED_DUTY_CYCLE_CH(index), &val);
+	clk_period = FIELD_GET(PWM_ASPEED_DUTY_CYCLE_PERIOD, val);
+	period = (NSEC_PER_SEC * BIT(div_h) * (div_l + 1) * (clk_period + 1));
+	period = DIV_ROUND_UP_ULL(period, rate);
+
+	return period;
+}
+
+static int aspeed_pwm_set_period(struct pwm_chip *chip, struct pwm_device *pwm,
+				 const struct pwm_state *state)
+{
+	struct device *dev = chip->dev;
+	struct aspeed_pwm_data *priv = aspeed_pwm_chip_to_data(chip);
+	unsigned long rate;
+	u64 div_h, div_l, divisor;
+	u32 index = pwm->hwpwm;
+
+	rate = clk_get_rate(priv->clk);
+	/*
+	 * Pick the smallest value for div_h so that div_l can be the biggest
+	 * which results in a finer resolution near the target period value.
+	 */
+	divisor = (u64)NSEC_PER_SEC * (PWM_ASPEED_FIXED_PERIOD + 1) *
+		  (FIELD_MAX(PWM_ASPEED_CTRL_CLK_DIV_L) + 1);
+	div_h = order_base_2(div64_u64(rate * state->period, divisor));
+	if (div_h > 0xf)
+		div_h = 0xf;
+
+	divisor = ((u64)NSEC_PER_SEC * (PWM_ASPEED_FIXED_PERIOD + 1)) << div_h;
+	div_l = div64_u64(rate * state->period, divisor);
+
+	if (div_l == 0)
+		return -ERANGE;
+
+	div_l -= 1;
+
+	if (div_l > 255)
+		div_l = 255;
+
+	dev_dbg(dev, "clk source: %ld div_h %lld, div_l : %lld\n", rate, div_h,
+		div_l);
+
+	regmap_update_bits(
+		priv->regmap, PWM_ASPEED_CTRL_CH(index),
+		(PWM_ASPEED_CTRL_CLK_DIV_H | PWM_ASPEED_CTRL_CLK_DIV_L),
+		FIELD_PREP(PWM_ASPEED_CTRL_CLK_DIV_H, div_h) |
+			FIELD_PREP(PWM_ASPEED_CTRL_CLK_DIV_L, div_l));
+	return 0;
+}
+
+static void aspeed_pwm_set_duty(struct pwm_chip *chip, struct pwm_device *pwm,
+				const struct pwm_state *state)
+{
+	struct device *dev = chip->dev;
+	struct aspeed_pwm_data *priv = aspeed_pwm_chip_to_data(chip);
+	u32 duty_pt;
+	u32 index = pwm->hwpwm;
+	u64 cur_period;
+
+	cur_period = aspeed_pwm_get_period(chip, pwm);
+	duty_pt = DIV_ROUND_DOWN_ULL(
+		state->duty_cycle * (PWM_ASPEED_FIXED_PERIOD + 1), cur_period);
+	dev_dbg(dev, "cur_period = %lld, duty_cycle = %lld, duty_pt = %d\n",
+		cur_period, state->duty_cycle, duty_pt);
+	if (duty_pt == 0) {
+		regmap_update_bits(priv->regmap, PWM_ASPEED_CTRL_CH(index),
+				   PWM_ASPEED_CTRL_CLK_ENABLE, 0);
+	} else {
+		if (duty_pt >= (PWM_ASPEED_FIXED_PERIOD + 1))
+			duty_pt = 0;
+		regmap_update_bits(
+			priv->regmap, PWM_ASPEED_DUTY_CYCLE_CH(index),
+			PWM_ASPEED_DUTY_CYCLE_FALLING_POINT,
+			FIELD_PREP(PWM_ASPEED_DUTY_CYCLE_FALLING_POINT,
+				   duty_pt));
+		regmap_update_bits(priv->regmap, PWM_ASPEED_CTRL_CH(index),
+				   PWM_ASPEED_CTRL_CLK_ENABLE,
+				   PWM_ASPEED_CTRL_CLK_ENABLE);
+	}
+}
+
+static void aspeed_pwm_get_state(struct pwm_chip *chip, struct pwm_device *pwm,
+				 struct pwm_state *state)
+{
+	struct device *dev = chip->dev;
+	struct aspeed_pwm_data *priv = aspeed_pwm_chip_to_data(chip);
+	u32 index = pwm->hwpwm;
+	bool polarity, ch_en, clk_en;
+	u32 duty_pt, val;
+
+	regmap_read(priv->regmap, PWM_ASPEED_CTRL_CH(index), &val);
+	polarity = FIELD_GET(PWM_ASPEED_CTRL_INVERSE, val);
+	ch_en = FIELD_GET(PWM_ASPEED_CTRL_PIN_ENABLE, val);
+	clk_en = FIELD_GET(PWM_ASPEED_CTRL_CLK_ENABLE, val);
+	regmap_read(priv->regmap, PWM_ASPEED_DUTY_CYCLE_CH(index), &val);
+	duty_pt = FIELD_GET(PWM_ASPEED_DUTY_CYCLE_FALLING_POINT, val);
+
+	state->period = aspeed_pwm_get_period(chip, pwm);
+	if (clk_en && duty_pt)
+		state->duty_cycle = DIV_ROUND_UP_ULL(
+			state->period * duty_pt, PWM_ASPEED_FIXED_PERIOD + 1);
+	else
+		state->duty_cycle = clk_en ? state->period : 0;
+	state->polarity = polarity;
+	state->enabled = ch_en;
+	dev_dbg(dev, "get period: %lldns, duty_cycle: %lldns", state->period,
+		state->duty_cycle);
+}
+
+static int aspeed_pwm_apply(struct pwm_chip *chip, struct pwm_device *pwm,
+			    const struct pwm_state *state)
+{
+	struct device *dev = chip->dev;
+	struct aspeed_pwm_data *priv = aspeed_pwm_chip_to_data(chip);
+	u32 index = pwm->hwpwm;
+	int ret;
+
+	dev_dbg(dev, "apply period: %lldns, duty_cycle: %lldns", state->period,
+		state->duty_cycle);
+
+	regmap_update_bits(priv->regmap, PWM_ASPEED_CTRL_CH(index),
+			   PWM_ASPEED_CTRL_PIN_ENABLE,
+			   state->enabled ? PWM_ASPEED_CTRL_PIN_ENABLE : 0);
+	/*
+	 * Fixed the period to the max value and rising point to 0
+	 * for high resolution and simplify frequency calculation.
+	 */
+	regmap_update_bits(priv->regmap, PWM_ASPEED_DUTY_CYCLE_CH(index),
+			   (PWM_ASPEED_DUTY_CYCLE_PERIOD |
+			    PWM_ASPEED_DUTY_CYCLE_RISING_POINT),
+			   FIELD_PREP(PWM_ASPEED_DUTY_CYCLE_PERIOD,
+				      PWM_ASPEED_FIXED_PERIOD));
+
+	ret = aspeed_pwm_set_period(chip, pwm, state);
+	if (ret)
+		return ret;
+	aspeed_pwm_set_duty(chip, pwm, state);
+	regmap_update_bits(priv->regmap, PWM_ASPEED_CTRL_CH(index),
+			   PWM_ASPEED_CTRL_INVERSE,
+			   FIELD_PREP(PWM_ASPEED_CTRL_INVERSE,
+				      state->polarity));
+	return 0;
+}
+
+static const struct pwm_ops aspeed_pwm_ops = {
+	.apply = aspeed_pwm_apply,
+	.get_state = aspeed_pwm_get_state,
+	.owner = THIS_MODULE,
+};
+
+static int aspeed_pwm_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	int ret;
+	struct aspeed_pwm_data *priv;
+	struct device_node *np;
+	struct platform_device *parent_dev;
+
+	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
+	if (!priv)
+		return -ENOMEM;
+
+	np = pdev->dev.parent->of_node;
+	if (!of_device_is_compatible(np, "aspeed,ast2600-pwm-tach"))
+		return dev_err_probe(dev, -ENODEV,
+				     "unsupported pwm device binding\n");
+
+	priv->regmap = syscon_node_to_regmap(np);
+	if (IS_ERR(priv->regmap))
+		return dev_err_probe(dev, PTR_ERR(priv->regmap),
+				     "couldn't get regmap\n");
+
+	parent_dev = of_find_device_by_node(np);
+	priv->clk = devm_clk_get(&parent_dev->dev, 0);
+	if (IS_ERR(priv->clk))
+		return dev_err_probe(dev, PTR_ERR(priv->clk),
+				     "couldn't get clock\n");
+
+	ret = clk_prepare_enable(priv->clk);
+	if (ret)
+		return dev_err_probe(dev, ret, "couldn't enable clock\n");
+
+	priv->reset = of_reset_control_get_shared(np, NULL);
+	if (IS_ERR(priv->reset))
+		return dev_err_probe(dev, PTR_ERR(priv->reset),
+				     "get reset failed\n");
+
+	ret = reset_control_deassert(priv->reset);
+	if (ret) {
+		dev_err(dev, "cannot deassert reset control: %pe\n",
+			ERR_PTR(ret));
+		goto err_disable_clk;
+	}
+
+	priv->chip.dev = dev;
+	priv->chip.ops = &aspeed_pwm_ops;
+	priv->chip.npwm = PWM_ASPEED_NR_PWMS;
+	priv->chip.of_xlate = of_pwm_xlate_with_flags;
+	priv->chip.of_pwm_n_cells = 3;
+
+	ret = pwmchip_add(&priv->chip);
+	if (ret < 0) {
+		dev_err(dev, "failed to add PWM chip: %pe\n", ERR_PTR(ret));
+		goto err_assert_reset;
+	}
+	dev_set_drvdata(dev, priv);
+	return 0;
+err_assert_reset:
+	reset_control_assert(priv->reset);
+err_disable_clk:
+	clk_disable_unprepare(priv->clk);
+	return ret;
+}
+
+static int aspeed_pwm_remove(struct platform_device *dev)
+{
+	struct aspeed_pwm_data *priv = platform_get_drvdata(dev);
+
+	pwmchip_remove(&priv->chip);
+	reset_control_assert(priv->reset);
+	clk_disable_unprepare(priv->clk);
+
+	return 0;
+}
+
+static const struct of_device_id of_pwm_match_table[] = {
+	{
+		.compatible = "aspeed,ast2600-pwm",
+	},
+	{},
+};
+MODULE_DEVICE_TABLE(of, of_pwm_match_table);
+
+static struct platform_driver aspeed_pwm_driver = {
+	.probe = aspeed_pwm_probe,
+	.remove	= aspeed_pwm_remove,
+	.driver	= {
+		.name = "aspeed_pwm",
+		.of_match_table = of_pwm_match_table,
+	},
+};
+
+module_platform_driver(aspeed_pwm_driver);
+
+MODULE_AUTHOR("Billy Tsai <billy_tsai@aspeedtech.com>");
+MODULE_DESCRIPTION("ASPEED PWM device driver");
+MODULE_LICENSE("GPL v2");