On 03/02/2021 14:45, Rob Herring wrote:
On Mon, Feb 1, 2021 at 2:21 AM Boris Brezillon
<boris.brezillon@xxxxxxxxxxxxx> 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>
---
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
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