linux-kernel - Re: [PATCH v9 15/15] drm/i915: Add deadline based boost support

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Date:   Fri, 3 Mar 2023 17:19:40 +0200
From:   Ville Syrjälä <ville.syrjala@...ux.intel.com>
To:     Rob Clark <robdclark@...il.com>
Cc:     Rob Clark <robdclark@...omium.org>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...el.com>,
        Christian König 
        <ckoenig.leichtzumerken@...il.com>,
        Michel Dänzer <michel@...nzer.net>,
        open list <linux-kernel@...r.kernel.org>,
        dri-devel@...ts.freedesktop.org,
        Christian König <christian.koenig@....com>,
        "moderated list:DMA BUFFER SHARING FRAMEWORK" 
        <linaro-mm-sig@...ts.linaro.org>,
        Pekka Paalanen <ppaalanen@...il.com>,
        Luben Tuikov <luben.tuikov@....com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Alex Deucher <alexander.deucher@....com>,
        Matt Turner <mattst88@...il.com>,
        freedreno@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org,
        Sumit Semwal <sumit.semwal@...aro.org>,
        "open list:DMA BUFFER SHARING FRAMEWORK" 
        <linux-media@...r.kernel.org>
Subject: Re: [PATCH v9 15/15] drm/i915: Add deadline based boost support

On Fri, Mar 03, 2023 at 05:00:03PM +0200, Ville Syrjälä wrote:
> On Fri, Mar 03, 2023 at 06:48:43AM -0800, Rob Clark wrote:
> > On Fri, Mar 3, 2023 at 1:58 AM Tvrtko Ursulin
> > <tvrtko.ursulin@...ux.intel.com> wrote:
> > >
> > >
> > > On 03/03/2023 03:21, Rodrigo Vivi wrote:
> > > > On Thu, Mar 02, 2023 at 03:53:37PM -0800, Rob Clark wrote:
> > > >> From: Rob Clark <robdclark@...omium.org>
> > > >>
> > > >
> > > > missing some wording here...
> > > >
> > > >> v2: rebase
> > > >>
> > > >> Signed-off-by: Rob Clark <robdclark@...omium.org>
> > > >> ---
> > > >>   drivers/gpu/drm/i915/i915_request.c | 20 ++++++++++++++++++++
> > > >>   1 file changed, 20 insertions(+)
> > > >>
> > > >> diff --git a/drivers/gpu/drm/i915/i915_request.c b/drivers/gpu/drm/i915/i915_request.c
> > > >> index 7503dcb9043b..44491e7e214c 100644
> > > >> --- a/drivers/gpu/drm/i915/i915_request.c
> > > >> +++ b/drivers/gpu/drm/i915/i915_request.c
> > > >> @@ -97,6 +97,25 @@ static bool i915_fence_enable_signaling(struct dma_fence *fence)
> > > >>      return i915_request_enable_breadcrumb(to_request(fence));
> > > >>   }
> > > >>
> > > >> +static void i915_fence_set_deadline(struct dma_fence *fence, ktime_t deadline)
> > > >> +{
> > > >> +    struct i915_request *rq = to_request(fence);
> > > >> +
> > > >> +    if (i915_request_completed(rq))
> > > >> +            return;
> > > >> +
> > > >> +    if (i915_request_started(rq))
> > > >> +            return;
> > > >
> > > > why do we skip the boost if already started?
> > > > don't we want to boost the freq anyway?
> > >
> > > I'd wager Rob is just copying the current i915 wait boost logic.
> > 
> > Yup, and probably incorrectly.. Matt reported fewer boosts/sec
> > compared to your RFC, this could be the bug
> 
> I don't think i915 calls drm_atomic_helper_wait_for_fences()
> so that could explain something.

Oh, I guess this wasn't even supposed to take over the current 
display boost stuff since you didn't remove the old one.

The current one just boosts after a missed vblank. The deadline
could use your timer approach I suppose and boost already a bit
earlier in the hopes of not missing the vblank.

-- 
Ville Syrjälä
Intel