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

[Stefan Wahren]

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.

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;
>   }
>