media: mt9m114: Avoid a reset low spike during probe()

mt9m114_probe() requests the reset GPIO in output low state:

	sensor->reset = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_LOW);

and then almost immediately afterwards calls mt9m114_power_on() which does:

		gpiod_set_value(sensor->reset, 1);
		fsleep(duration);
		gpiod_set_value(sensor->reset, 0);

which means that if the reset pin was high before this code runs that
it will very briefly be driven low because of passing GPIOD_OUT_LOW when
requesting the GPIO only to be driven high again possibly directly after
that. Such a very brief driving low of the reset pin may put the chip in
a confused state.

Request the GPIO in high (reset the chip) state instead to avoid this,
turning the initial gpiod_set_value() in mt9m114_power_on() into a no-op.
and the fsleep() ensures that it will stay high long enough to properly
reset the chip.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans de Goede <johannes.goede@oss.qualcomm.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>

diff --git a/drivers/media/i2c/mt9m114.c b/drivers/media/i2c/mt9m114.c
index a45e6709d1082e981d368fefb895ab8d5f5e27f9..910eefa915c7e2c24d52068ff5f855e4b774ca2b 100644 (file)
--- a/drivers/media/i2c/mt9m114.c
+++ b/drivers/media/i2c/mt9m114.c
@@ -2467,7 +2467,7 @@ static int mt9m114_probe(struct i2c_client *client)
                goto error_ep_free;
        }
 
-       sensor->reset = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_LOW);
+       sensor->reset = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
        if (IS_ERR(sensor->reset)) {
                ret = PTR_ERR(sensor->reset);
                dev_err_probe(dev, ret, "Failed to get reset GPIO\n");