Hi Jacek,
On Fri, Nov 17, 2017 at 6:51 PM, Jacek Anaszewski
<jacek.anaszewski@xxxxxxxxx> wrote:
> On power down event brightness is set to 0 on each registered
> LED class device that set LED_CORE_SUSPENDRESUME flag (leds-pwm does).
>
> It may be the case that pwm subsystem (or underlaying bus used by
> particular controller) is suspended before LED subsystem, or the
> culprit is the generic LED subsystem workqueue in which brightness
> setting events are queued for drivers that use brightness_set_blocking
> op (leds-pwm case).
Thanks for your comments.
I realized that this issue can be fixed inside drivers/pwm/pwm-imx.c :
--- a/drivers/pwm/pwm-imx.c
+++ b/drivers/pwm/pwm-imx.c
@@ -35,6 +35,7 @@
#define MX3_PWMSAR 0x0C /* PWM Sample Register */
#define MX3_PWMPR 0x10 /* PWM Period Register */
#define MX3_PWMCR_PRESCALER(x) ((((x) - 1) & 0xFFF) << 4)
+#define MX3_PWMCR_STOPEN (1 << 25)
#define MX3_PWMCR_DOZEEN (1 << 24)
#define MX3_PWMCR_WAITEN (1 << 23)
#define MX3_PWMCR_DBGEN (1 << 22)
@@ -209,7 +210,7 @@ static int imx_pwm_apply_v2(struct pwm_chip *chip,
struct pwm_device *pwm,
writel(duty_cycles, imx->mmio_base + MX3_PWMSAR);
writel(period_cycles, imx->mmio_base + MX3_PWMPR);
- cr = MX3_PWMCR_PRESCALER(prescale) |
+ cr = MX3_PWMCR_PRESCALER(prescale) | MX3_PWMCR_STOPEN |
MX3_PWMCR_DOZEEN | MX3_PWMCR_WAITEN |
MX3_PWMCR_DBGEN | MX3_PWMCR_CLKSRC_IPG_HIGH |
MX3_PWMCR_EN;
Setting the STOPEN bit, which "keeps PWM functional while in stop
mode" does the trick.
Maybe I will convert this into an optional device tree property to
keep the original behavior.
Thanks
