Messages in this thread | | | Date | Mon, 30 Mar 2020 18:10:23 +0200 | From | Clemens Gruber <> | Subject | Re: [PATCH 1/4] pwm: pca9685: remove unused duty_cycle struct element |
| |
On Mon, Mar 30, 2020 at 06:02:38PM +0200, Thierry Reding wrote: > On Mon, Mar 30, 2020 at 04:18:22PM +0300, Andy Shevchenko wrote: > > On Mon, Mar 30, 2020 at 4:09 PM Thierry Reding <thierry.reding@gmail.com> wrote: > > > > > > On Wed, Feb 26, 2020 at 02:52:26PM +0100, Matthias Schiffer wrote: > > > > duty_cycle was only set, never read. > > > > > > > > Signed-off-by: Matthias Schiffer <matthias.schiffer@ew.tq-group.com> > > > > --- > > > > drivers/pwm/pwm-pca9685.c | 4 ---- > > > > 1 file changed, 4 deletions(-) > > > > > > Applied, thanks. > > > > I'm not sure this patch is correct. > > What makes you say that? If you look at the code, the driver sets this > field to either 0 or some duty cycle value but ends up never using it. > Why would it be wrong to remove that code? > > > We already have broken GPIO in this driver. Do we need more breakage? > > My understanding is that nobody was able to pinpoint exactly when this > regressed, or if this only worked by accident to begin with. It sounds > like Clemens has a way of testing this driver, so perhaps we can solve > that GPIO issue while we're at it. > > The last discussion on this seems to have been around the time when you > posted a fix for it: > > https://patchwork.ozlabs.org/patch/1156012/ > > But then Sven had concerns that that also wasn't guaranteed to work: > > https://lkml.org/lkml/2019/6/2/73 > > So I think we could either apply your patch to restore the old behaviour > which I assume you tested, so at least it seems to work in practice, > even if there's still a potential race that Sven pointed out in the > above link. > > I'd prefer something alternative because it's obviously confusing and > completely undocumented. Mika had already proposed something that's a > little bit better, though still somewhat confusing. > > Oh... actually reading further through those threads there seems to be a > patch from Sven that was reviewed by Mika but then nothing happened: > > https://lkml.org/lkml/2019/6/4/1039 > > with the corresponding patchwork URL: > > https://patchwork.ozlabs.org/patch/1110083/ > > Andy, Clemens, do you have a way of testing the GPIO functionality of > this driver? If so, it'd be great if you could check the above patch > from Sven to fix PWM/GPIO interop.
Yes. I'll have a look and report back in a few days.
Clemens
| |