[Intel-gfx] [PATCH] drm/i915: Use 18 fast wake fast wake AUX sync len

[Hogander, Jouni]

On Tue, 2023-05-30 at 09:06 +0000, Murthy, Arun R wrote:
> > -----Original Message-----
> > From: Intel-gfx <intel-gfx-bounces at lists.freedesktop.org> On Behalf
> > Of Jouni
> > Högander
> > Sent: Monday, May 29, 2023 6:30 PM
> > To: intel-gfx at lists.freedesktop.org
> > Subject: [Intel-gfx] [PATCH] drm/i915: Use 18 fast wake fast wake
> > AUX sync
> > len
> > 
> > HW default for wake sync pulses is 18. 10 precarge and 8 preamble.
> > There is
> > no reason to change this especially as it is causing problems with
> > certain eDP
> > panels.
> > 
> > Signed-off-by: Jouni Högander <jouni.hogander at intel.com>
> > Fixes: 605f7c731333 ("drm/i915: Fix fast wake AUX sync len")
> > Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/8475
> > ---
> >  drivers/gpu/drm/i915/display/intel_dp_aux.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/display/intel_dp_aux.c
> > b/drivers/gpu/drm/i915/display/intel_dp_aux.c
> > index 0c27db8ae4f1..197c6e81db14 100644
> > --- a/drivers/gpu/drm/i915/display/intel_dp_aux.c
> > +++ b/drivers/gpu/drm/i915/display/intel_dp_aux.c
> > @@ -129,7 +129,7 @@ static int intel_dp_aux_sync_len(void)
> > 
> >  static int intel_dp_aux_fw_sync_len(void)  {
> > -       int precharge = 16; /* 10-16 */
> > +       int precharge = 10; /* 10-16 */
> 
> Is this change required in intel_dp_aux_sync_len() as well?

That is a good question. The issue is triggered with certain PSR panels
and only fast wake sync len impacts PSR sequence -> definetely it's not
in scope of this patch.

BR,

Jouni Högander

> 
> Thanks and Regards,
> Arun R Murthy
> --------------------
> 
> >         int preamble = 8;
> > 
> >         return precharge + preamble;
> > --
> > 2.34.1
>