linux-kernel - [PATCH v2 2/2] media: qcom: camss: Fix ordering of pm_runtime

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Message-Id: <20240716-linux-next-24-07-13-camss-fixes-v2-2-e60c9f6742f2@linaro.org>
Date: Tue, 16 Jul 2024 23:13:25 +0100
From: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To: Robert Foss <rfoss@...nel.org>, Todor Tomov <todor.too@...il.com>, 
 Mauro Carvalho Chehab <mchehab@...nel.org>, 
 Hans Verkuil <hansverk@...co.com>, Hans Verkuil <hverkuil-cisco@...all.nl>, 
 Milen Mitkov <quic_mmitkov@...cinc.com>
Cc: linux-media@...r.kernel.org, linux-arm-msm@...r.kernel.org, 
 linux-kernel@...r.kernel.org, 
 Mauro Carvalho Chehab <mchehab+samsung@...nel.org>, 
 Johan Hovold <johan+linaro@...nel.org>, 
 Bryan O'Donoghue <bryan.odonoghue@...aro.org>, stable@...r.kernel.org
Subject: [PATCH v2 2/2] media: qcom: camss: Fix ordering of
 pm_runtime_enable

pm_runtime_enable() should happen prior to vfe_get() since vfe_get() calls
pm_runtime_resume_and_get().

This is a basic race condition that doesn't show up for most users so is
not widely reported. If you blacklist qcom-camss in modules.d and then
subsequently modprobe the module post-boot it is possible to reliably show
this error up.

The kernel log for this error looks like this:

qcom-camss ac5a000.camss: Failed to power up pipeline: -13

Fixes: 02afa816dbbf ("media: camss: Add basic runtime PM support")
Reported-by: Johan Hovold <johan+linaro@...nel.org>
Closes: https://lore.kernel.org/lkml/ZoVNHOTI0PKMNt4_@hovoldconsulting.com/
Tested-by: Johan Hovold <johan+linaro@...nel.org>
Cc: <stable@...r.kernel.org>
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
---
 drivers/media/platform/qcom/camss/camss.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/media/platform/qcom/camss/camss.c b/drivers/media/platform/qcom/camss/camss.c
index 51b1d3550421..d64985ca6e88 100644
--- a/drivers/media/platform/qcom/camss/camss.c
+++ b/drivers/media/platform/qcom/camss/camss.c
@@ -2283,6 +2283,8 @@ static int camss_probe(struct platform_device *pdev)
 
 	v4l2_async_nf_init(&camss->notifier, &camss->v4l2_dev);
 
+	pm_runtime_enable(dev);
+
 	num_subdevs = camss_of_parse_ports(camss);
 	if (num_subdevs < 0) {
 		ret = num_subdevs;
@@ -2323,8 +2325,6 @@ static int camss_probe(struct platform_device *pdev)
 		}
 	}
 
-	pm_runtime_enable(dev);
-
 	return 0;
 
 err_register_subdevs:
@@ -2332,6 +2332,7 @@ static int camss_probe(struct platform_device *pdev)
 err_v4l2_device_unregister:
 	v4l2_device_unregister(&camss->v4l2_dev);
 	v4l2_async_nf_cleanup(&camss->notifier);
+	pm_runtime_disable(dev);
 err_genpd_cleanup:
 	camss_genpd_cleanup(camss);
 

-- 
2.45.2