Hi Stefan,
On 02/03/26 19:43, Stefan Wahren wrote:
Hi Maíra,
Am 18.02.26 um 21:45 schrieb Maíra Canal:
The bcm2835_asb_control() function uses a tight polling loop to wait
for the ASB bridge to acknowledge a request. During intensive workloads,
this handshake intermittently fails for V3D's master ASB on BCM2711,
resulting in "Failed to disable ASB master for v3d" errors during
runtime PM suspend. As a consequence, the failed power-off leaves V3D in
a broken state, leading to bus faults or system hangs on later accesses.
As the timeout is insufficient in some scenarios, increase the polling
timeout from 1us to 5us, which is still negligible in the context of a
power domain transition. Also, move the start timestamp to after the
MMIO write, as the write latency is counted against the timeout,
reducing the effective wait time for the hardware to respond.
so this bug has been discovered by this series and doesn't need to
backported?
I only found out about this bug when I was testing this series, but it's
quite possible that this issue also happened in other scenarios.
I remember complete system freezes during suspend to idle causes by V3D
on Raspberry CM4 [1]. But I never had the time to investigate further.
Regardless, this patch is
Reviewed-by: Stefan Wahren <[email protected]>
Thanks for the review! Ulf, considering Stefan's comment, I'd appreciate
if you could pick this patch and add the stable tag. Thanks.
Best regards,
- Maíra
Thanks
[1] - https://github.com/lategoodbye/linux-dev/
commit/6af3f79da5b5a41b37aefa6abe3d368c9ef09805
Signed-off-by: Maíra Canal <[email protected]>
---
drivers/pmdomain/bcm/bcm2835-power.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/drivers/pmdomain/bcm/bcm2835-power.c b/drivers/pmdomain/
bcm/bcm2835-power.c
index
1d29addfe036348e82293693b4059e504bb25575..7b9eea10a24e26835deeca84c60ccb616b99a508 100644
--- a/drivers/pmdomain/bcm/bcm2835-power.c
+++ b/drivers/pmdomain/bcm/bcm2835-power.c
@@ -166,8 +166,6 @@ static int bcm2835_asb_control(struct
bcm2835_power *power, u32 reg, bool enable
break;
}
- start = ktime_get_ns();
-
/* Enable the module's async AXI bridges. */
if (enable) {
val = readl(base + reg) & ~ASB_REQ_STOP;
@@ -176,9 +174,10 @@ static int bcm2835_asb_control(struct
bcm2835_power *power, u32 reg, bool enable
}
writel(PM_PASSWORD | val, base + reg);
+ start = ktime_get_ns();
while (!!(readl(base + reg) & ASB_ACK) == enable) {
cpu_relax();
- if (ktime_get_ns() - start >= 1000)
+ if (ktime_get_ns() - start >= 5000)
return -ETIMEDOUT;
}
