Now alvium_set_power tests if Alvium is up and running already
instead of waiting for the period of a full reboot. This safes
about 5-7 seconds delay for each connected camera what is already
booted especially when using multiple Alvium cameras or using
camera arrays.
The new function alvium_check is used by read_poll_timeout to check
whether a camera is connected on I2C and if it responds already.

Signed-off-by: Martin Hecht <mhecht73@gmail.com>
---
changes since v2:
- remove unused variable dev in alvium_check

changes since v1:
- added alvium_check to be used by read_poll_timeout as
  suggested by Sakari
---
 drivers/media/i2c/alvium-csi2.c | 31 ++++++++++++++++++++++++-------
 1 file changed, 24 insertions(+), 7 deletions(-)

diff --git a/drivers/media/i2c/alvium-csi2.c b/drivers/media/i2c/alvium-csi2.c
index 26cac5821b9f..6d2c3d62137c 100644
--- a/drivers/media/i2c/alvium-csi2.c
+++ b/drivers/media/i2c/alvium-csi2.c
@@ -433,10 +433,8 @@ static int alvium_is_alive(struct alvium_dev *alvium)
 
 	alvium_read(alvium, REG_BCRM_MINOR_VERSION_R, &bcrm, &ret);
 	alvium_read(alvium, REG_BCRM_HEARTBEAT_RW, &hbeat, &ret);
-	if (ret)
-		return ret;
 
-	return hbeat;
+	return ret;
 }
 
 static void alvium_print_avail_mipi_fmt(struct alvium_dev *alvium)
@@ -2354,8 +2352,24 @@ static int alvium_get_dt_data(struct alvium_dev *alvium)
 	return -EINVAL;
 }
 
+static int alvium_check(struct alvium_dev *alvium, u64 *bcrm_major)
+{
+	int ret = 0;
+
+	ret = alvium_read(alvium, REG_BCRM_MAJOR_VERSION_R, bcrm_major, NULL);
+
+	if (ret)
+		return ret;
+
+	if (*bcrm_major != 0)
+		return 0;
+
+	return -ENODEV;
+}
+
 static int alvium_set_power(struct alvium_dev *alvium, bool on)
 {
+	u64 bcrm_major = 0;
 	int ret;
 
 	if (!on)
@@ -2365,9 +2379,12 @@ static int alvium_set_power(struct alvium_dev *alvium, bool on)
 	if (ret)
 		return ret;
 
-	/* alvium boot time 7s */
-	msleep(7000);
-	return 0;
+	/* alvium boot time is up to 7.5s but test if its available already */
+	read_poll_timeout(alvium_check, bcrm_major, (bcrm_major == 0),
+		250000, 7500000, false,
+		alvium, &bcrm_major);
+
+	return ret;
 }
 
 static int alvium_runtime_resume(struct device *dev)
@@ -2432,7 +2449,7 @@ static int alvium_probe(struct i2c_client *client)
 	if (ret)
 		goto err_powerdown;
 
-	if (!alvium_is_alive(alvium)) {
+	if (alvium_is_alive(alvium)) {
 		ret = -ENODEV;
 		dev_err_probe(dev, ret, "Device detection failed\n");
 		goto err_powerdown;
-- 
2.43.0