[Intel-gfx] [PATCH] drm/i915/psr: Split sel fetch plane configuration into arm and noarm

[Lucas De Marchi]

On Fri, Jan 27, 2023 at 07:12:29PM +0200, Luca Coelho wrote:
>On Fri, 2023-01-27 at 16:37 +0200, Jani Nikula wrote:
>> On Fri, 27 Jan 2023, Tvrtko Ursulin <tvrtko.ursulin at linux.intel.com> wrote:
>> > On 26/01/2023 16:05, Jani Nikula wrote:
>> > > On Thu, 26 Jan 2023, Luca Coelho <luca at coelho.fi> wrote:
>> > > > On Thu, 2023-01-26 at 14:11 +0200, Luca Coelho wrote:
>> > > > > On Thu, 2023-01-26 at 14:00 +0200, Jani Nikula wrote:
>> > > > > > On Thu, 26 Jan 2023, Luca Coelho <luca at coelho.fi> wrote:
>> > > > > > > On Wed, 2023-01-25 at 12:44 +0200, Jouni Högander wrote:
>> > > > > > > > > diff --git a/drivers/gpu/drm/i915/display/intel_psr.c b/drivers/gpu/drm/i915/display/intel_psr.c
>> > > > > > > > > index 7d4a15a283a0..63b79c611932 100644
>> > > > > > > > > --- a/drivers/gpu/drm/i915/display/intel_psr.c
>> > > > > > > > > +++ b/drivers/gpu/drm/i915/display/intel_psr.c
>> > > > > > > > > @@ -1559,7 +1559,26 @@ void intel_psr2_disable_plane_sel_fetch(struct intel_plane *plane,
>> > > > > > > > >   	intel_de_write_fw(dev_priv, PLANE_SEL_FETCH_CTL(pipe, plane->id), 0);
>> > > > > > > > >   }
>> > > > > > > > >
>> > > > > > > > > -void intel_psr2_program_plane_sel_fetch(struct intel_plane *plane,
>> > > > > > > > > +void intel_psr2_program_plane_sel_fetch_arm(struct intel_plane *plane,
>> > > > > > > > > +					const struct intel_crtc_state *crtc_state,
>> > > > > > > > > +					const struct intel_plane_state *plane_state,
>> > > > > > > > > +					int color_plane)
>> > > > > > > > > +{
>> > > > > > > > > +	struct drm_i915_private *dev_priv = to_i915(plane->base.dev);
>> > > > > > >
>> > > > > > > Should you use i915 instead of dev_priv? I've heard and read elsewhere
>> > > > > > > that this is generally a desired change.  Much easier to use always the
>> > > > > > > same local name for this kind of thing.  Though this file is already
>> > > > > > > interspersed with both versions...
>> > > > > >
>> > > > > > Basically the only reason to use dev_priv for new code is to deal with
>> > > > > > some register macros that still have implicit dev_priv in
>> > > > > > them. Otherwise, i915 should be used, and when convenient, dev_priv
>> > > > > > should be converted to i915 while touching the code anyway (in a
>> > > > > > separate patch, but while you're there).
>> > > > >
>> > > > > Thanks for the clarification! In this case we're not using any of the
>> > > > > macros, AFAICT, so I guess it's better to go with i915 already? And I
>> > > > > think it should even be in this same patch, since it's a new function
>> > > > > anyway.
>> > > > >
>> > > > >
>> > > > > > The implicit dev_priv dependencies in the register macros are a bit
>> > > > > > annoying to fix, and it's been going slow. In retrospect maybe the right
>> > > > > > thing would have been to just sed the parameter to all of them
>> > > > > > everywhere and be done with it for good. Not too late now, I guess, and
>> > > > > > I'd take the patches in a heartbeat if someone were to step up and do
>> > > > > > it.
>> > > > >
>> > > > > I see that there is a boatload of register macros using it... I won't
>> > > > > promise, but I think it would be a good exercise for a n00b like me to
>> > > > > make this patch, though I already foresee another boatload of conflicts
>> > > > > with the internal trees and everything...
>> > > >
>> > > > There were actually 10 boatloads of places to change:
>> > > >
>> > > >   187 files changed, 12104 insertions(+), 12104 deletions(-)
>> > > >
>> > > > ...but it _does_ compile. 😄
>> > > >
>> > > > Do you think this is fine? Lots of shuffle, but if you think it's okay,
>> > > > I can send the patch out now.
>> > >
>> > > Heh, I said I'd take patchES, not everything together! ;)
>> > >
>> > > Rodrigo, Tvrtko, Joonas, thoughts?
>> >
>> > IMO if the elimination of implicit dev_priv is not included then I am
>> > not sure the churn is worth the effort.
>> >
>> > I think one trap is that it is easy to assume solving those conflicts is
>> > easy because there is a script, somewhere, whatever, but one needs to be
>> > careful with assuming a random person hitting a merge conflict will
>> > realize there is a script, know where to find it, and know how to use it
>> > against a state where conflict markers are sitting in their local tree.
>> > That's a lot of assumed knowledge which my experience tells me is not
>> > universally there.
>> >
>> > Having said all that, I looked at the occurrence histogram for the
>> > proposed churn and gut feel says conflicts wouldn't even be that bad
>> > since they seem heavily localized in a handful of files plus the display
>> > subdir.
>> >
>> > Plus it is upstream.. so we are allowed not to care too much about
>> > backporting woes. I would still hope implicit dev_priv, albeit
>> > orthogonal, would be coming somewhat together with the rename. For that
>> > warm fuzzy feeling that the churn was really really worth it.
>>
>> I was mostly talking about the implicit dev_priv removal. It's somewhat
>> easy, because you can always assume dev_priv is around when the macros
>> in question are used.
>>
>> The above is a dependency to any renames. I don't think the renames are
>> as important as removing the implicit dev_priv, and the renames are
>> easier to handle piecemeal, say a file at a time or something.
>
>I'm trying to write a semantic patch to convert this stuff.  But
>coccinelle is problematic when it comes to macros, so it turned out not
>to be as trivial as I though.

I think that the definition in the header is easier to do manually and
let coccinelle change only the users. I started this and it seems to be
going the right direction:

2 prerequisite commits:
https://git.kernel.org/pub/scm/linux/kernel/git/demarchi/linux.git/log/?h=tip-drm-intel-dev-priv

$ cat /tmp/a.cocci
virtual patch

@@
expression e;
@@
- DPLL(e)
+ DPLL(dev_priv, e)

@@
expression e;
@@
- DPLL_MD(e)
+ DPLL_MD(dev_priv, e)

@@
expression e1, e2;
@@
- PALETTE(e1, e2)
+ PALETTE(dev_priv, e1, e2)

... simply continuing with the same pattern for the other macros
I *think* would produce a good result. I slightly tested it with
`make coccicheck MODE=patch COCCI=/tmp/a.cocci  M=./drivers/gpu/drm/i915`

Then if we change the macro in i915_reg.h we could remove all the
implicit deps. Wether we should pass dev_priv or mmio_base I think will
vary from macro to macro.  The rename s/dev_priv/i915/ being the cherry
on top.

Lucas De Marchi

>
>Now that I've been looking at the code more, so I see the issue with
>the implicit dev_priv in some of the macros.  But I think that is
>really trivial to solve.  It shouldn't be an issue to add a parameter
>to those macros.  It will probably need some manual work, but I'm on it
>and hopefully will be able to send some patches as RFC.
>
>--
>Cheers,
>Luca.