Re: [PATCH v3 0/2] drm/i915/display: Power request asserting/deasserting

[Raag Jadav <raag.jadav@intel.com>]

On Thu, Oct 31, 2024 at 07:58:19PM +0530, Kahola, Mika wrote:
> > -----Original Message-----
> > From: Jadav, Raag <raag.jadav@intel.com>
> > Sent: Thursday, 31 October 2024 14.59
> > To: Kahola, Mika <mika.kahola@intel.com>
> > Cc: intel-gfx@lists.freedesktop.org; Sousa, Gustavo <gustavo.sousa@intel.com>;
> > jani.nikula@linux.intel.com
> > Subject: Re: [PATCH v3 0/2] drm/i915/display: Power request
> > asserting/deasserting
> > 
> > On Thu, Oct 31, 2024 at 01:40:25PM +0200, Mika Kahola wrote:
> > > There is a HW issue that arises when there are race conditions between
> > > TCSS entering/exiting TC7 or TC10 states while the driver is
> > > asserting/deasserting TCSS power request. As a workaround, Display
> > > driver will implement a mailbox sequence to ensure that the TCSS is in
> > > TC0 when TCSS power request is asserted/deasserted.
> > >
> > > The sequence is the following
> > >
> > > 1. Read mailbox command status and wait until run/busy bit is
> > >    clear
> > > 2. Write mailbox data value '1' for power request asserting
> > >    and '0' for power request deasserting 3. Write mailbox command
> > > run/busy bit and command value with 0x1 4. Read mailbox command and
> > > wait until run/busy bit is clear
> > >    before continuing power request.
> > >
> > > while at it, let's start using struct intel_display instead of struct
> > > drm_i915_private as well.
> > 
> > Perhaps this needs to be its own patch since it's unrelated to the series.
> 
> There was a request from Jani to start using intel_display instead of
> drm_i915_private also with the calling function. So this is perhaps
> remotely related to this WA I included this here.

Yes, he has a series WIP for it. Perhaps worth collaborating.

Raag