[PATCH v7 2/5] pmdomain: bcm: bcm2835-power: Increase ASB control timeout

[Ulf Hansson]

On Thu, 12 Mar 2026 at 22:35, Maíra Canal <mcanal at igalia.com> wrote:
>
> 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.
>
> Cc: stable at vger.kernel.org
> Reviewed-by: Stefan Wahren <wahrenst at gmx.net>
> Signed-off-by: Maíra Canal <mcanal at igalia.com>
>
> ---
> To: Ulf Hansson <ulf.hansson at linaro.org>
> To: Ray Jui <rjui at broadcom.com>
> To: Scott Branden <sbranden at broadcom.com>
> Cc: linux-pm at vger.kernel.org
> ---
>  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 0450202bbee2513c9116a36abaa839b460550935..1815eb4ee69b9b672b5e314402f1cc9897c57dcb 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;
>         }

Please consider replacing the above polling-loop with
readl_poll_timeout() or use another one that fits better from the
similar helpers.

Kind regards
Uffe