Re: [PATCH] pwm: stm32: add comment to better describe breakinput feature
From: Uwe Kleine-König
Date: Thu Oct 10 2019 - 03:07:59 EST
On Wed, Oct 09, 2019 at 11:51:05AM +0200, Fabrice Gasnier wrote:
> On 10/8/19 4:45 PM, Uwe Kleine-König wrote:
> > On Tue, Oct 08, 2019 at 01:41:27PM +0200, Fabrice Gasnier wrote:
> >> Add a comment to better describe the purpose of breakinput feature that
> >> can be found on some STM32 timer instances. Briefly comment on the
> >> characteristics of this input for PWM, and pinmuxing as suggested in .
> >>  https://lkml.org/lkml/2019/10/1/207
> >> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@xxxxxx>
> >> ---
> >> drivers/pwm/pwm-stm32.c | 8 +++++++-
> >> 1 file changed, 7 insertions(+), 1 deletion(-)
> >> diff --git a/drivers/pwm/pwm-stm32.c b/drivers/pwm/pwm-stm32.c
> >> index 359b085..6406ebb 100644
> >> --- a/drivers/pwm/pwm-stm32.c
> >> +++ b/drivers/pwm/pwm-stm32.c
> >> @@ -522,8 +522,14 @@ static int stm32_pwm_apply_breakinputs(struct stm32_pwm *priv,
> >> sizeof(struct stm32_breakinput));
> >> /*
> >> + * Some timer instances can have BRK input pins (e.g. basically a fault
> >> + * pin from the output power stage). The break feature allows a safe
> >> + * shut-down of the PWM outputs to a predefined state. Further details
> >> + * are available in application note AN4277, "Using STM32 device PWM
> >> + * shut-down features..."
> > Without having read the application note I don't understand the purpose.
> > Not sure if this should be a show stopper though.
> Hi Uwe,
> I can rephrase this. Do you think the bellow comment would be more
> relevant and easy to understand ?
> * The break feature allows a safe shut-down of the PWM outputs.
> * It's based on the BRK event signal defined in the dt-bindings
> * by <index level filter> values.
> * Because "st,breakinput" parameter is optional do not make probe
> * failed if it doesn't exist.
I still fail to understand. This is an input that determines the actual
value of the output pin? What makes a shutdown of outputs safe? What is
a shutdown anyhow?
Apart from that: s/do not make probe failed/don't fail to probe/.
Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | http://www.pengutronix.de/ |