Re: [PATCH 1/1] drm/panel: truly: Add additional delay after pulling down reset gpio

[Vivek Gautam]

On 5/28/2019 2:13 PM, Marc Gonzalez wrote:
> On 27/05/2019 12:26, Vivek Gautam wrote:
>
> > MTP SDM845 panel seems to need additional delay to bring panel
> > to a workable state. Running modetest without this change displays
> > blurry artifacts.
> >
> > Signed-off-by: Vivek Gautam <vivek.gautam@xxxxxxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/panel/panel-truly-nt35597.c | 1 +
> >   1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/gpu/drm/panel/panel-truly-nt35597.c b/drivers/gpu/drm/panel/panel-truly-nt35597.c
> > index fc2a66c53db4..aa7153fd3be4 100644
> > --- a/drivers/gpu/drm/panel/panel-truly-nt35597.c
> > +++ b/drivers/gpu/drm/panel/panel-truly-nt35597.c
> > @@ -280,6 +280,7 @@ static int truly_35597_power_on(struct truly_nt35597 *ctx)
> >   	gpiod_set_value(ctx->reset_gpio, 1);
> >   	usleep_range(10000, 20000);
> >   	gpiod_set_value(ctx->reset_gpio, 0);
> > +	usleep_range(10000, 20000);
> I'm not sure usleep_range() makes sense with these values.
>
> AFAIU, usleep_range() is typically used for sub-jiffy sleeps, and is based
> on HRT to generate an interrupt.
>
> Once we get into jiffy granularity, it seems to me msleep() is good enough.
> IIUC, it would piggy-back on the jiffy timer interrupt.
>
> In short, why not just use msleep(10); ?

I am just maintaining the symmetry across older code.

Thanks
Vivek
> Regards.