media: i2c: max9271: Introduce wake_up() function

The MAX9271 chip manual prescribes a delay of 5 milliseconds
after the chip exits from low power state.

Add a new function to the max9271 library driver that wakes up the chip
with a dummy i2c transaction and implements the correct delay of 5
milliseconds after the chip exits from low power state.

Use the newly introduced function in the rdacm20 and rdacm21 camera
drivers. The former was not respecting the required delay while the
latter was waiting for a too-short timeout.

Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

1 files changed, 12 insertions, 0 deletions

diff --git a/drivers/media/i2c/max9271.c b/drivers/media/i2c/max9271.c
index 2c7dc7fb9846..ff86c8c4ea61 100644
--- a/drivers/media/i2c/max9271.c
+++ b/drivers/media/i2c/max9271.c
@@ -80,6 +80,18 @@ static int max9271_pclk_detect(struct max9271_device *dev)
 	return -EIO;
 }
 
+void max9271_wake_up(struct max9271_device *dev)
+{
+	/*
+	 * Use the chip default address as this function has to be called
+	 * before any other one.
+	 */
+	dev->client->addr = MAX9271_DEFAULT_ADDR;
+	i2c_smbus_read_byte(dev->client);
+	usleep_range(5000, 8000);
+}
+EXPORT_SYMBOL_GPL(max9271_wake_up);
+
 int max9271_set_serial_link(struct max9271_device *dev, bool enable)
 {
 	int ret;