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

[Ulf Hansson]

On Wed, 18 Mar 2026 at 13:54, Maíra Canal <mcanal at igalia.com> wrote:
>
> 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].

The first version of the patch moved the call to ktime_get_ns(), so I
thought we might as well use readl_poll_timeout_atomic() directly,
instead of fixing up the open-coded loop.

Kind regards
Uffe

>
> [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;
> >>   }
> >>
> >
>