Re: [Intel-gfx] [PATCH 3/8] drm/i915/pcode: Extend pcode functions for multiple gt's

["Dixit, Ashutosh" <ashutosh.dixit@intel.com>]

On Fri, 15 Apr 2022 03:21:26 -0700, Rodrigo Vivi wrote:
> On Thu, Apr 14, 2022 at 03:31:07PM -0700, Dixit, Ashutosh wrote:
> > On Thu, 14 Apr 2022 06:28:57 -0700, Jani Nikula wrote:
> > >
> > > On Wed, 13 Apr 2022, Ashutosh Dixit <ashutosh.dixit@intel.com> wrote:
> > > > Each gt contains an independent instance of pcode. Extend pcode functions
> > > > to interface with pcode on different gt's. Previous (GT0) pcode read/write
> > > > interfaces are preserved.
> > >
> > > The big problem here is that this hard couples display code to gt code,
> > > while we're trying hard to go the opposite direction. It doesn't matter
> > > that the existing interfaces are preserved as wrappers when it relies on
> > > an intel_gt being available (via i915->gt0).
>
> I don't believe there is a big problem in here...
>
> please note the intel_pcode.h is keeping the abstraction for display
>
> #define snb_pcode_write_timeout(i915, mbox, val, fast_timeout_us, slow_timeout_ms) \
>         intel_gt_pcode_write_timeout(&(i915)->gt0, mbox, val, fast_timeout_us, slow_timeout_ms)
>
> #define snb_pcode_write(i915, mbox, val) \
>         snb_pcode_write_timeout(i915, mbox, val, 500, 0)
>
> display only uses these macros that Ashutosh didn't touch.
>
> > >
> > > Note how 'git grep intel_gt -- drivers/gpu/drm/i915/display/' matches
> > > only 1 line.
>
> As well with the patches applied:
>
> $ git log --oneline -1
> 1f58f1195478 (HEAD -> drm-tip) drm/i915/gt: Expose per-gt RPS defaults in sysfs
>
> $ git grep intel_gt -- drivers/gpu/drm/i915/display/
> drivers/gpu/drm/i915/display/intel_display.c:           intel_gt_set_wedged(to_gt(dev_priv));
>
> >
> > Hi Jani, would you have suggestions about how to do this (handle pcode on
> > multiple gt's)? The thinking was this patch would be a straightforward way
> > to avoid code duplication. Also:
>
> Maybe it is just a matter of renaming the macros used by display
> in intel_pcode.h to reflect that it should be used by display only?

In v2 I have added a patch ([PATCH 4/9] drm/i915/gt: Convert callers to
user per-gt pcode functions) which correctly calls per-gt pcode functions
where this is required. With this patch only display functions (and one
other caller) are left calling the "global scope" snb_pcode_read/write*
functions. So the legacy snb_pcode_read/write* are now basically being used
only by display. Let's see if Jani is ok with this. Thanks.