linux-kernel - [PATCH v2 1/2] media: i2c: imx290: Check for availability in probe()

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Message-Id: <20240828-imx290-avail-v2-1-bd320ac8e8fa@skidata.com>
Date: Wed, 28 Aug 2024 20:13:07 +0200
From: Benjamin Bara <bbara93@...il.com>
To: Mauro Carvalho Chehab <mchehab@...nel.org>, 
 Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, 
 Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc: Hans de Goede <hdegoede@...hat.com>, 
 Laurent Pinchart <laurent.pinchart@...asonboard.com>, 
 Alexander Stein <alexander.stein@...tq-group.com>, 
 linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Benjamin Bara <benjamin.bara@...data.com>
Subject: [PATCH v2 1/2] media: i2c: imx290: Check for availability in
 probe()

Currently, the V4L2 subdevice is also created when the device is not
available/connected. In this case, dmesg shows the following:

[   10.419510] imx290 7-001a: Error writing reg 0x301c: -6
[   10.428981] imx290 7-001a: Error writing reg 0x3020: -6
[   10.442712] imx290 7-001a: Error writing reg 0x3018: -6
[   10.454018] imx290 7-001a: Error writing reg 0x3020: -6

which seems to come from imx290_ctrl_update() after the subdev init is
finished. However, as the errors are ignored, the subdev is initialized
but simply does not work. From userspace perspective, there is no
visible difference between a working and not-working subdevice (except
when trying it out or watching for the error message).

This commit adds a simple availability check before starting with the
subdev initialization to error out instead.

Signed-off-by: Benjamin Bara <benjamin.bara@...data.com>
---
Changes since v1:
- define operating/standby mode and use it
- read out the standby mode during probe and ensure it is standby
---
 drivers/media/i2c/imx290.c | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/drivers/media/i2c/imx290.c b/drivers/media/i2c/imx290.c
index 4150e6e4b9a6..2a869576600c 100644
--- a/drivers/media/i2c/imx290.c
+++ b/drivers/media/i2c/imx290.c
@@ -29,6 +29,8 @@
 #include <media/v4l2-subdev.h>
 
 #define IMX290_STANDBY					CCI_REG8(0x3000)
+#define IMX290_STANDBY_OPERATING			(0 << 0)
+#define IMX290_STANDBY_STANDBY				(1 << 0)
 #define IMX290_REGHOLD					CCI_REG8(0x3001)
 #define IMX290_XMSTA					CCI_REG8(0x3002)
 #define IMX290_ADBIT					CCI_REG8(0x3005)
@@ -1016,7 +1018,7 @@ static int imx290_start_streaming(struct imx290 *imx290,
 		return ret;
 	}
 
-	cci_write(imx290->regmap, IMX290_STANDBY, 0x00, &ret);
+	cci_write(imx290->regmap, IMX290_STANDBY, IMX290_STANDBY_OPERATING, &ret);
 
 	msleep(30);
 
@@ -1029,7 +1031,7 @@ static int imx290_stop_streaming(struct imx290 *imx290)
 {
 	int ret = 0;
 
-	cci_write(imx290->regmap, IMX290_STANDBY, 0x01, &ret);
+	cci_write(imx290->regmap, IMX290_STANDBY, IMX290_STANDBY_STANDBY, &ret);
 
 	msleep(30);
 
@@ -1520,6 +1522,7 @@ static int imx290_probe(struct i2c_client *client)
 {
 	struct device *dev = &client->dev;
 	struct imx290 *imx290;
+	u64 val;
 	int ret;
 
 	imx290 = devm_kzalloc(dev, sizeof(*imx290), GFP_KERNEL);
@@ -1580,6 +1583,16 @@ static int imx290_probe(struct i2c_client *client)
 	pm_runtime_set_autosuspend_delay(dev, 1000);
 	pm_runtime_use_autosuspend(dev);
 
+	/* Make sure the sensor is available before V4L2 subdev init. */
+	ret = cci_read(imx290->regmap, IMX290_STANDBY, &val, NULL);
+	if (ret)
+		goto err_pm;
+	if (val != IMX290_STANDBY_STANDBY) {
+		dev_err(dev, "Sensor is not in standby mode\n");
+		ret = -ENODEV;
+		goto err_pm;
+	}
+
 	/* Initialize the V4L2 subdev. */
 	ret = imx290_subdev_init(imx290);
 	if (ret)

-- 
2.46.0