[PATCH v6 3/6] pmdomain: bcm: bcm2835-power: Increase ASB control timeout

[Maíra Canal]

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 <wahrenst at gmx.net>

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 <mcanal at igalia.com>
>> ---
>>   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;
>>       }
>>
>