[PATCH 1/2] pmdomain: bcm: bcm2835-power: Increase ASB control timeout

[Maíra Canal]

Hi Stefan,

On 18/03/26 08:51, Stefan Wahren wrote:
> Hi Maíra,
> 
> Am 17.03.26 um 23:41 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, replace the open-coded ktime_get_ns()/
>> cpu_relax() polling loop with readl_poll_timeout_atomic().
> personally I would have moved all readl_poll_timeout_atomic changes in 
> the second patch, to avoid possible conflicts in stable. But no strong 
> opinion about this.
> 

TBH personally, I also agree. But, as I don't have a strong opinion
about it, I prioritized addressing Ulf's feedback in the last version
[1].

[1] 
https://lore.kernel.org/dri-devel/20260312-v3d-power-management-v7-0-9f006a1d4c55@igalia.com/T/#mf96146960ec7ffeea32e732c95ccf9548af21748

Best regards,
- Maíra

> Best regards
>>
>> Cc: stable at vger.kernel.org
>> Fixes: 670c672608a1 ("soc: bcm: bcm2835-pm: Add support for power 
>> domains under a new binding.")
>> Signed-off-by: Maíra Canal <mcanal at igalia.com>
>> ---
>>   drivers/pmdomain/bcm/bcm2835-power.c | 12 ++++--------
>>   1 file changed, 4 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/pmdomain/bcm/bcm2835-power.c b/drivers/pmdomain/ 
>> bcm/bcm2835-power.c
>> index 
>> 0450202bbee2513c9116a36abaa839b460550935..eee87a3005325848547ce1f5fd729b168a641460 100644
>> --- a/drivers/pmdomain/bcm/bcm2835-power.c
>> +++ b/drivers/pmdomain/bcm/bcm2835-power.c
>> @@ -9,6 +9,7 @@
>>   #include <linux/clk.h>
>>   #include <linux/delay.h>
>>   #include <linux/io.h>
>> +#include <linux/iopoll.h>
>>   #include <linux/mfd/bcm2835-pm.h>
>>   #include <linux/module.h>
>>   #include <linux/platform_device.h>
>> @@ -153,7 +154,6 @@ struct bcm2835_power {
>>   static int bcm2835_asb_control(struct bcm2835_power *power, u32 reg, 
>> bool enable)
>>   {
>>       void __iomem *base = power->asb;
>> -    u64 start;
>>       u32 val;
>>       switch (reg) {
>> @@ -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;
>> @@ -176,11 +174,9 @@ static int bcm2835_asb_control(struct 
>> bcm2835_power *power, u32 reg, bool enable
>>       }
>>       writel(PM_PASSWORD | val, base + reg);
>> -    while (!!(readl(base + reg) & ASB_ACK) == enable) {
>> -        cpu_relax();
>> -        if (ktime_get_ns() - start >= 1000)
>> -            return -ETIMEDOUT;
>> -    }
>> +    if (readl_poll_timeout_atomic(base + reg, val,
>> +                      !!(val & ASB_ACK) != enable, 0, 5))
>> +        return -ETIMEDOUT;
>>       return 0;
>>   }
>>
>