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

[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.

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;
 	}
 

-- 
2.53.0