[Freedreno] [PATCH v3 1/2] drm/msm/dpu: Modify vblank_refcount if error in callback

[Dmitry Baryshkov]

On Fri, 1 Dec 2023 at 21:14, Abhinav Kumar <quic_abhinavk at quicinc.com> wrote:
>
>
>
> On 11/30/2023 11:45 PM, Dmitry Baryshkov wrote:
> > On Fri, 1 Dec 2023 at 03:41, Paloma Arellano <quic_parellan at quicinc.com> wrote:
> >>
> >> When the irq callback returns a value other than zero,
> >> modify vblank_refcount by performing the inverse
> >> operation of its corresponding if-else condition.
> >
> > I think it might be better to follow Bjorn's suggestion: once we have
> > the lock, we don't need atomics at all.
> > Then you rearrange the code to set the new value after getting return
> > code from dpu_core_irq_register_callback() /
> > dpu_core_irq_unregister_callback().
> >
>
> Even if we drop the atomics, we will have to replace it with a simple
> refcount. The refcount checks will be before calling
> dpu_core_irq_register_callback() / dpu_core_irq_unregister_callback().
>
> So we will still need the corresponding inverse refcount when either of
> those calls fail but just that they wont be atomics.

Within the critical section you can check the value before
register_callback and increment it afterwards if registration
succeeds.

>
> Am I missing something here?
>
> >>
> >> Signed-off-by: Paloma Arellano <quic_parellan at quicinc.com>
> >> ---
> >>   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_cmd.c | 9 +++++++--
> >>   drivers/gpu/drm/msm/disp/dpu1/dpu_encoder_phys_vid.c | 9 +++++++--
> >>   2 files changed, 14 insertions(+), 4 deletions(-)
> >



-- 
With best wishes
Dmitry