From 472ac3dcac108d6648ee28616c6de1e3b0bb361f Mon Sep 17 00:00:00 2001 From: Alexandre Belloni Date: Mon, 25 May 2015 18:11:49 +0200 Subject: pwm: atmel: Fix incorrect CDTY value after disabling MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Acked-by: Nicolas Ferre Tested-by: Gaël PORTAY Signed-off-by: Thierry Reding --- drivers/pwm/pwm-atmel.c | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) (limited to 'drivers/pwm') 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 +#include #include #include #include +#include #include #include #include @@ -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); } -- cgit v1.2.3-70-g09d2