linux-kernel - [PATCH v3 2/2] firmware: exynos-acpm: allow use during system shutdown

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Message-Id: <20250325-acpm-atomic-v3-2-c66aae7df925@linaro.org>
Date: Tue, 25 Mar 2025 09:46:08 +0000
From: André Draszik <andre.draszik@...aro.org>
To: Tudor Ambarus <tudor.ambarus@...aro.org>, 
 Krzysztof Kozlowski <krzk@...nel.org>, 
 Alim Akhtar <alim.akhtar@...sung.com>
Cc: Peter Griffin <peter.griffin@...aro.org>, 
 Will McVicker <willmcvicker@...gle.com>, kernel-team@...roid.com, 
 linux-kernel@...r.kernel.org, linux-samsung-soc@...r.kernel.org, 
 linux-arm-kernel@...ts.infradead.org, 
 André Draszik <andre.draszik@...aro.org>
Subject: [PATCH v3 2/2] firmware: exynos-acpm: allow use during system
 shutdown

We need to access the PMIC during late system shutdown and at that time
we are not allowed to sleep anymore.

To make this case work, and since we can't detect this case in a
non-racy way, switch to using udelay() unconditionally, instead of
usleep_range().

Signed-off-by: André Draszik <andre.draszik@...aro.org>
---
v3:
* use udelay() unconditionally (Krzysztof)
* drop previous Rb tag

udelay(20) causes a checkpatch --strict warning (it suggests to use
usleep_range() instead for usec >= 10), but that's exactly what we can
not do.
Reducing the udelay to be smaller than 10 will generally cause the loop
to be iterated more than once, which I wanted to avoid.
I could reflow the code to hide the actual value from checkpatch, e.g.
with the help of a local variable if that is preferred to ignoring the
checkpatch warning.
---
 drivers/firmware/samsung/exynos-acpm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/firmware/samsung/exynos-acpm.c b/drivers/firmware/samsung/exynos-acpm.c
index 542eaff03f9e39422a8c5345ca75e05c1710a9ee..379da420b9eb3fcbca5461bec7e2de6bf0774659 100644
--- a/drivers/firmware/samsung/exynos-acpm.c
+++ b/drivers/firmware/samsung/exynos-acpm.c
@@ -300,7 +300,7 @@ static int acpm_dequeue_by_polling(struct acpm_chan *achan,
 			return 0;
 
 		/* Determined experimentally. */
-		usleep_range(20, 30);
+		udelay(20);
 	} while (ktime_before(ktime_get(), timeout));
 
 	dev_err(dev, "Timeout! ch:%u s:%u bitmap:%lx.\n",

-- 
2.49.0.395.g12beb8f557-goog