[PATCH 3/3] media: i2c: ov8856: Power off the sensor during system suspend

[Babis Danias via B4 Relay]

From: Babis Danias <b.danias@xxxxxxxxxxxx>

On a Dell Latitude 7320 Detachable, the rear OV8856 stays powered for
the whole of s2idle once the dw9714 VCM driver is bound, even with the
camera idle. Tracing a 20 second suspend shows the sensor's clock and
regulators enabled about 0.5 s after "PM: suspend entry", and disabled
only just before "PM: suspend exit". Without the VCM driver bound, they
stay off.

ipu-bridge links the VCM to the sensor with a runtime PM device link,
which makes the sensor a supplier of the VCM. The dw9714 driver has
system sleep callbacks, so the VCM can't use direct-complete, and
dpm_clear_superiors_direct_complete() then clears direct_complete for
the sensor as well. The sensor goes through the full system suspend
path, where acpi_subsys_suspend() runtime-resumes it before calling the
driver's suspend callback. But ov8856 has had no system sleep callbacks
since commit 19ae6ba57f88 ("media: i2c: ov8856: Drop system suspend and
resume handlers"), so nothing powers the sensor off again.

This matters since commit 609a71568664 ("media: i2c: ov8856 : remove
ACPI node bypass mechanism") made the runtime PM callbacks control the
sensor's power on ACPI systems.

Use DEFINE_RUNTIME_DEV_PM_OPS(), so that pm_runtime_force_suspend()
powers the sensor off during system suspend, and
pm_runtime_force_resume() powers it on again only if it was in use. With
this, the sensor is off for the whole suspend. It is still powered up
for a few milliseconds at suspend entry, by acpi_subsys_suspend().

The problem was found, and this patch written, with the help of an AI
coding assistant (Claude Opus 5.5). See the cover letter for details.

Fixes: 609a71568664 ("media: i2c: ov8856 : remove ACPI node bypass mechanism")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Babis Danias <b.danias@xxxxxxxxxxxx>
---
 drivers/media/i2c/ov8856.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/media/i2c/ov8856.c b/drivers/media/i2c/ov8856.c
index f9bcdd412..848e981ff 100644
--- a/drivers/media/i2c/ov8856.c
+++ b/drivers/media/i2c/ov8856.c
@@ -2462,9 +2462,8 @@ static int ov8856_probe(struct i2c_client *client)
 	return ret;
 }
 
-static const struct dev_pm_ops ov8856_pm_ops = {
-	SET_RUNTIME_PM_OPS(ov8856_power_off, ov8856_power_on, NULL)
-};
+static DEFINE_RUNTIME_DEV_PM_OPS(ov8856_pm_ops, ov8856_power_off,
+				 ov8856_power_on, NULL);
 
 #ifdef CONFIG_ACPI
 static const struct acpi_device_id ov8856_acpi_ids[] = {
@@ -2484,7 +2483,7 @@ MODULE_DEVICE_TABLE(of, ov8856_of_match);
 static struct i2c_driver ov8856_i2c_driver = {
 	.driver = {
 		.name = "ov8856",
-		.pm = &ov8856_pm_ops,
+		.pm = pm_ptr(&ov8856_pm_ops),
 		.acpi_match_table = ACPI_PTR(ov8856_acpi_ids),
 		.of_match_table = ov8856_of_match,
 	},

-- 
2.56.0