linux-kernel - [PATCH] media: i2c: ov2659: speedup probe if no device connected

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Message-ID: <1450706086-6801-1-git-send-email-grygorii.strashko@ti.com>
Date:	Mon, 21 Dec 2015 15:54:46 +0200
From:	Grygorii Strashko <grygorii.strashko@...com>
To:	"Lad, Prabhakar" <prabhakar.csengg@...il.com>,
	Mauro Carvalho Chehab <mchehab@....samsung.com>
CC:	<linux-media@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Grygorii Strashko <grygorii.strashko@...com>,
	Benoit Parrot <bparrot@...com>
Subject: [PATCH] media: i2c: ov2659: speedup probe if no device connected

The ov2659 driver performs device detection and initialization in the
following way:
 - send reset command REG_SOFTWARE_RESET
 - load array of predefined register's setting (~150 values)
 - read device version REG_SC_CHIP_ID_H/REG_SC_CHIP_ID_L
 - check version and exit if invalid.

As result, for not connected device there will be >~150 i2c transactions
executed before device version checking and exit (there are no
failures detected because ov2659 declared as I2C_CLIENT_SCCB and NACKs
are ignored in this case).

Let's fix that by checking the chip version first and start
initialization only if it's supported.

Cc: Benoit Parrot <bparrot@...com>
Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>
---
 drivers/media/i2c/ov2659.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/media/i2c/ov2659.c b/drivers/media/i2c/ov2659.c
index 49109f4..9b7b78c 100644
--- a/drivers/media/i2c/ov2659.c
+++ b/drivers/media/i2c/ov2659.c
@@ -1321,10 +1321,6 @@ static int ov2659_detect(struct v4l2_subdev *sd)
 	}
 	usleep_range(1000, 2000);
 
-	ret = ov2659_init(sd, 0);
-	if (ret < 0)
-		return ret;
-
 	/* Check sensor revision */
 	ret = ov2659_read(client, REG_SC_CHIP_ID_H, &pid);
 	if (!ret)
@@ -1338,8 +1334,10 @@ static int ov2659_detect(struct v4l2_subdev *sd)
 			dev_err(&client->dev,
 				"Sensor detection failed (%04X, %d)\n",
 				id, ret);
-		else
+		else {
 			dev_info(&client->dev, "Found OV%04X sensor\n", id);
+			ret = ov2659_init(sd, 0);
+		}
 	}
 
 	return ret;
-- 
2.6.4

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