| Message ID | 1432570309-17819-1-git-send-email-alexandre.belloni@free-electrons.com |
|---|---|
| State | Accepted |
| Headers | show |
Le 25/05/2015 18:11, Alexandre Belloni a écrit : > pwm-leds calls .config() and .disable() in a row. This exhibits that it may > happen that the channel gets disabled before CDTY has been updated with CUPD. > The issue gets quite worse with long periods. > So, ensure that at least one period has past before disabling the channel by > polling ISR. > > Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com> > --- > I had the previous patch tested on a multicolor LED and unfortunately, the delay > is not nice in that case. I wanted to avoid a mutex. > This version uses a variable to store the state of the update of the pwm. This > is reset everytime is gets a new configuration and updated when it is disabled > or another pwm is configured. > When disabling a multicolor LED, we only wait for the first pwm to update then > we remember that we already seen the other one having their period expire and it > looks much better. It seems valid: Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com> Thanks! > > drivers/pwm/pwm-atmel.c | 28 ++++++++++++++++++++++++++++ > 1 file changed, 28 insertions(+) > > > diff --git a/drivers/pwm/pwm-atmel.c b/drivers/pwm/pwm-atmel.c > index 89f9ca41d9af..a947c9095d9d 100644 > --- a/drivers/pwm/pwm-atmel.c > +++ b/drivers/pwm/pwm-atmel.c > @@ -8,9 +8,11 @@ > */ > > #include <linux/clk.h> > +#include <linux/delay.h> > #include <linux/err.h> > #include <linux/io.h> > #include <linux/module.h> > +#include <linux/mutex.h> > #include <linux/of.h> > #include <linux/of_device.h> > #include <linux/platform_device.h> > @@ -21,6 +23,7 @@ > #define PWM_ENA 0x04 > #define PWM_DIS 0x08 > #define PWM_SR 0x0C > +#define PWM_ISR 0x1C > /* Bit field in SR */ > #define PWM_SR_ALL_CH_ON 0x0F > > @@ -60,6 +63,9 @@ struct atmel_pwm_chip { > struct clk *clk; > void __iomem *base; > > + unsigned int updated_pwms; > + struct mutex isr_lock; /* ISR is cleared when read, ensure only one thread does that */ > + > void (*config)(struct pwm_chip *chip, struct pwm_device *pwm, > unsigned long dty, unsigned long prd); > }; > @@ -144,6 +150,10 @@ static int atmel_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, > val = (val & ~PWM_CMR_CPRE_MSK) | (pres & PWM_CMR_CPRE_MSK); > atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWM_CMR, val); > atmel_pwm->config(chip, pwm, dty, prd); > + mutex_lock(&atmel_pwm->isr_lock); > + atmel_pwm->updated_pwms |= atmel_pwm_readl(atmel_pwm, PWM_ISR); > + atmel_pwm->updated_pwms &= ~(1 << pwm->hwpwm); > + mutex_unlock(&atmel_pwm->isr_lock); > > clk_disable(atmel_pwm->clk); > return ret; > @@ -243,7 +253,22 @@ static int atmel_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm) > static void atmel_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm) > { > struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip); > + unsigned long timeout = jiffies + 2 * HZ; > + > + /* > + * Wait for at least a complete period to have passed before disabling a > + * channel to be sure that CDTY has been updated > + */ > + mutex_lock(&atmel_pwm->isr_lock); > + atmel_pwm->updated_pwms |= atmel_pwm_readl(atmel_pwm, PWM_ISR); > + > + while (!(atmel_pwm->updated_pwms & (1 << pwm->hwpwm)) && > + time_before(jiffies, timeout)) { > + usleep_range(10, 100); > + atmel_pwm->updated_pwms |= atmel_pwm_readl(atmel_pwm, PWM_ISR); > + } > > + mutex_unlock(&atmel_pwm->isr_lock); > atmel_pwm_writel(atmel_pwm, PWM_DIS, 1 << pwm->hwpwm); > > clk_disable(atmel_pwm->clk); > @@ -358,6 +383,8 @@ static int atmel_pwm_probe(struct platform_device *pdev) > atmel_pwm->chip.npwm = 4; > atmel_pwm->chip.can_sleep = true; > atmel_pwm->config = data->config; > + atmel_pwm->updated_pwms = 0; > + mutex_init(&atmel_pwm->isr_lock); > > ret = pwmchip_add(&atmel_pwm->chip); > if (ret < 0) { > @@ -379,6 +406,7 @@ static int atmel_pwm_remove(struct platform_device *pdev) > struct atmel_pwm_chip *atmel_pwm = platform_get_drvdata(pdev); > > clk_unprepare(atmel_pwm->clk); > + mutex_destroy(&atmel_pwm->isr_lock); > > return pwmchip_remove(&atmel_pwm->chip); > } >
On Mon, May 25, 2015 at 06:11:49PM +0200, Alexandre Belloni wrote: > pwm-leds calls .config() and .disable() in a row. This exhibits that it may > happen that the channel gets disabled before CDTY has been updated with CUPD. > The issue gets quite worse with long periods. > So, ensure that at least one period has past before disabling the channel by > polling ISR. > > Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com> > --- > I had the previous patch tested on a multicolor LED and unfortunately, the delay > is not nice in that case. I wanted to avoid a mutex. > This version uses a variable to store the state of the update of the pwm. This > is reset everytime is gets a new configuration and updated when it is disabled > or another pwm is configured. > When disabling a multicolor LED, we only wait for the first pwm to update then > we remember that we already seen the other one having their period expire and it > looks much better. > > drivers/pwm/pwm-atmel.c | 28 ++++++++++++++++++++++++++++ > 1 file changed, 28 insertions(+) Applied, thanks. Thierry -- To unsubscribe from this list: send the line "unsubscribe linux-pwm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/pwm/pwm-atmel.c b/drivers/pwm/pwm-atmel.c index 89f9ca41d9af..a947c9095d9d 100644 --- a/drivers/pwm/pwm-atmel.c +++ b/drivers/pwm/pwm-atmel.c @@ -8,9 +8,11 @@ */ #include <linux/clk.h> +#include <linux/delay.h> #include <linux/err.h> #include <linux/io.h> #include <linux/module.h> +#include <linux/mutex.h> #include <linux/of.h> #include <linux/of_device.h> #include <linux/platform_device.h> @@ -21,6 +23,7 @@ #define PWM_ENA 0x04 #define PWM_DIS 0x08 #define PWM_SR 0x0C +#define PWM_ISR 0x1C /* Bit field in SR */ #define PWM_SR_ALL_CH_ON 0x0F @@ -60,6 +63,9 @@ struct atmel_pwm_chip { struct clk *clk; void __iomem *base; + unsigned int updated_pwms; + struct mutex isr_lock; /* ISR is cleared when read, ensure only one thread does that */ + void (*config)(struct pwm_chip *chip, struct pwm_device *pwm, unsigned long dty, unsigned long prd); }; @@ -144,6 +150,10 @@ static int atmel_pwm_config(struct pwm_chip *chip, struct pwm_device *pwm, val = (val & ~PWM_CMR_CPRE_MSK) | (pres & PWM_CMR_CPRE_MSK); atmel_pwm_ch_writel(atmel_pwm, pwm->hwpwm, PWM_CMR, val); atmel_pwm->config(chip, pwm, dty, prd); + mutex_lock(&atmel_pwm->isr_lock); + atmel_pwm->updated_pwms |= atmel_pwm_readl(atmel_pwm, PWM_ISR); + atmel_pwm->updated_pwms &= ~(1 << pwm->hwpwm); + mutex_unlock(&atmel_pwm->isr_lock); clk_disable(atmel_pwm->clk); return ret; @@ -243,7 +253,22 @@ static int atmel_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm) static void atmel_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm) { struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip); + unsigned long timeout = jiffies + 2 * HZ; + + /* + * Wait for at least a complete period to have passed before disabling a + * channel to be sure that CDTY has been updated + */ + mutex_lock(&atmel_pwm->isr_lock); + atmel_pwm->updated_pwms |= atmel_pwm_readl(atmel_pwm, PWM_ISR); + + while (!(atmel_pwm->updated_pwms & (1 << pwm->hwpwm)) && + time_before(jiffies, timeout)) { + usleep_range(10, 100); + atmel_pwm->updated_pwms |= atmel_pwm_readl(atmel_pwm, PWM_ISR); + } + mutex_unlock(&atmel_pwm->isr_lock); atmel_pwm_writel(atmel_pwm, PWM_DIS, 1 << pwm->hwpwm); clk_disable(atmel_pwm->clk); @@ -358,6 +383,8 @@ static int atmel_pwm_probe(struct platform_device *pdev) atmel_pwm->chip.npwm = 4; atmel_pwm->chip.can_sleep = true; atmel_pwm->config = data->config; + atmel_pwm->updated_pwms = 0; + mutex_init(&atmel_pwm->isr_lock); ret = pwmchip_add(&atmel_pwm->chip); if (ret < 0) { @@ -379,6 +406,7 @@ static int atmel_pwm_remove(struct platform_device *pdev) struct atmel_pwm_chip *atmel_pwm = platform_get_drvdata(pdev); clk_unprepare(atmel_pwm->clk); + mutex_destroy(&atmel_pwm->isr_lock); return pwmchip_remove(&atmel_pwm->chip); }
pwm-leds calls .config() and .disable() in a row. This exhibits that it may happen that the channel gets disabled before CDTY has been updated with CUPD. The issue gets quite worse with long periods. So, ensure that at least one period has past before disabling the channel by polling ISR. Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com> --- I had the previous patch tested on a multicolor LED and unfortunately, the delay is not nice in that case. I wanted to avoid a mutex. This version uses a variable to store the state of the update of the pwm. This is reset everytime is gets a new configuration and updated when it is disabled or another pwm is configured. When disabling a multicolor LED, we only wait for the first pwm to update then we remember that we already seen the other one having their period expire and it looks much better. drivers/pwm/pwm-atmel.c | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+)