On 03/02/2021 14:45, Rob Herring wrote:
On Mon, Feb 1, 2021 at 2:21 AM Boris Brezillon boris.brezillon@collabora.com 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@collabora.com
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;Can't we avoid the goto? Change the for loop like this:
i = 0; while (status = mmu_read(pfdev, MMU_INT_RAWSTAT)) { ...
i++; if (i == 16) i = 0;}
Well that reads from the RAWSTAT register excessively (which could be expensive at low GPU clock speeds), but we could do:
for(i = 0; status; i++) { ...
if (!status) { i = 0; status = mmu_read(pfdev, MMU_INT_RAWSTAT); } }
(or similar with a while() if you prefer). Of course we could even get rid of the 'i' loop altogether:
status = mmu_read(pfdev, MMU_INT_RAWSTAT); while (status) { int i = ffs(status | (status >> 16)) - 1;
... existing code ...
status &= ~mask; if (!status) status = mmu_read(pfdev, MMU_INT_RAWSTAT); }
Steve
mmu_write(pfdev, MMU_INT_MASK, ~0); return IRQ_HANDLED;};
2.26.2