From: Dmitry Eremin-Solenikov <[email protected]> Writing several values to PWMSAR register with PWM being disabled can lead to FIFO (connected to PWMSAR) being overflown. Then after enabling PWM, hardware will use stale values. Instead cache the duty cycles and write them to the hardware only before enabling PWM.
Signed-off-by: Dmitry Eremin-Solenikov <[email protected]> --- drivers/pwm/pwm-imx.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/drivers/pwm/pwm-imx.c b/drivers/pwm/pwm-imx.c index c735127..79c2b24 100644 --- a/drivers/pwm/pwm-imx.c +++ b/drivers/pwm/pwm-imx.c @@ -46,6 +46,7 @@ struct imx_chip { struct clk *clk_ipg; void __iomem *mmio_base; + unsigned long duty_cycles; struct pwm_chip chip; @@ -105,7 +106,7 @@ static int imx_pwm_config_v2(struct pwm_chip *chip, { struct imx_chip *imx = to_imx_chip(chip); unsigned long long c; - unsigned long period_cycles, duty_cycles, prescale; + unsigned long period_cycles, prescale; u32 cr; c = clk_get_rate(imx->clk_per); @@ -118,7 +119,7 @@ static int imx_pwm_config_v2(struct pwm_chip *chip, period_cycles /= prescale; c = (unsigned long long)period_cycles * duty_ns; do_div(c, period_ns); - duty_cycles = c; + imx->duty_cycles = c; /* * according to imx pwm RM, the real period value should be @@ -134,7 +135,8 @@ static int imx_pwm_config_v2(struct pwm_chip *chip, period_cycles -= 2; - writel(duty_cycles, imx->mmio_base + MX3_PWMSAR); + if (test_bit(PWMF_ENABLED, &pwm->flags)) + writel(imx->duty_cycles, imx->mmio_base + MX3_PWMSAR); writel(period_cycles, imx->mmio_base + MX3_PWMPR); cr = readl(imx->mmio_base + MX3_PWMCR); @@ -157,6 +159,9 @@ static void imx_pwm_set_enable_v2(struct pwm_chip *chip, bool enable) struct imx_chip *imx = to_imx_chip(chip); u32 val; + if (enable) + writel(imx->duty_cycles, imx->mmio_base + MX3_PWMSAR); + val = readl(imx->mmio_base + MX3_PWMCR); if (enable) -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-pwm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
