On Mon, 1 Feb 2021 13:24:00 +0000
Steven Price <steven.price@xxxxxxx> wrote:
> On 01/02/2021 12:59, Boris Brezillon wrote:
> > On Mon, 1 Feb 2021 12:13:49 +0000
> > Steven Price <steven.price@xxxxxxx> wrote:
> >
> >> On 01/02/2021 08:21, Boris Brezillon wrote:
> >>> Doing a hw-irq -> threaded-irq round-trip is counter-productive, stay
> >>> in the threaded irq handler as long as we can.
> >>>
> >>> Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxxxx>
> >>
> >> Looks fine to me, but I'm interested to know if you actually saw a
> >> performance improvement. Back-to-back MMU faults should (hopefully) be
> >> fairly uncommon.
> >
> > I actually didn't check the perf improvement or the actual number of
> > back-to-back MMU faults, but
> > dEQP-GLES31.functional.draw_indirect.compute_interop.large.drawelements_combined_grid_1000x1000_drawcount_5000
> > seemed to generate a few of those, so I thought it'd be good to
> > optimize that case given how trivial it is.
>
> Fair enough! I was just a little concerned that Panfrost was somehow
> provoking enough interrupts that this was a measurable performance
> improvement.
>
> I assume you'll push these to drm-misc-next (/fixes) as appropriate.
I think I'll just queue everything to misc-next and let the stable
maintainers backport the fixes (no one complained about this issue so
far).
>
> Thanks,
>
> Steve
>
> >>
> >> Regardless:
> >>
> >> Reviewed-by: Steven Price <steven.price@xxxxxxx>
> >>
> >>> ---
> >>> drivers/gpu/drm/panfrost/panfrost_mmu.c | 7 +++++++
> >>> 1 file changed, 7 insertions(+)
> >>>
> >>> diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> >>> index 21e552d1ac71..65bc20628c4e 100644
> >>> --- a/drivers/gpu/drm/panfrost/panfrost_mmu.c
> >>> +++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c
> >>> @@ -580,6 +580,8 @@ static irqreturn_t panfrost_mmu_irq_handler_thread(int irq, void *data)
> >>> u32 status = mmu_read(pfdev, MMU_INT_RAWSTAT);
> >>> int i, ret;
> >>>
> >>> +again:
> >>> +
> >>> for (i = 0; status; i++) {
> >>> u32 mask = BIT(i) | BIT(i + 16);
> >>> u64 addr;
> >>> @@ -628,6 +630,11 @@ static irqreturn_t panfrost_mmu_irq_handler_thread(int irq, void *data)
> >>> status &= ~mask;
> >>> }
> >>>
> >>> + /* If we received new MMU interrupts, process them before returning. */
> >>> + status = mmu_read(pfdev, MMU_INT_RAWSTAT);
> >>> + if (status)
> >>> + goto again;
> >>> +
> >>> mmu_write(pfdev, MMU_INT_MASK, ~0);
> >>> return IRQ_HANDLED;
> >>> };
> >>>
> >>
> >
>
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