linux-kernel - [PATCH v4 3/5] media: i2c: ov5645: Increase tolerance of external clock frequency

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Date:   Thu, 19 Mar 2020 12:19:21 +0000
From:   Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Kieran Bingham <kieran.bingham+renesas@...asonboard.com>
Cc:     linux-media@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Lad Prabhakar <prabhakar.csengg@...il.com>,
        Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: [PATCH v4 3/5] media: i2c: ov5645: Increase tolerance of external clock frequency

While testing on Renesas RZ/G2E platform, noticed the clock frequency to
be 24242424 as a result the probe failed.

This patch increases the tolerance to 5% so that it avoids patching for
new platforms and it warns the users if the frequency is not within the
range and continue further in the probe instead of returning failure.

Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
---
 drivers/media/i2c/ov5645.c | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/drivers/media/i2c/ov5645.c b/drivers/media/i2c/ov5645.c
index e298acdadeef..52a185ed4368 100644
--- a/drivers/media/i2c/ov5645.c
+++ b/drivers/media/i2c/ov5645.c
@@ -1105,13 +1105,11 @@ static int ov5645_probe(struct i2c_client *client)
 		}
 	}
 
-	/* external clock must be 24MHz, allow 1% tolerance */
+	/* ideally external clock must be 24MHz, allow 5% tolerance */
 	xclk_freq = clk_get_rate(ov5645->xclk);
-	if (xclk_freq < 23760000 || xclk_freq > 24240000) {
-		dev_err(dev, "external clock frequency %u is not supported\n",
-			xclk_freq);
-		return -EINVAL;
-	}
+	if (xclk_freq < 22800000 || xclk_freq > 25200000)
+		dev_warn(dev, "external clock frequency is set to %u, sensor might misbehave\n",
+			 xclk_freq);
 
 	for (i = 0; i < OV5645_NUM_SUPPLIES; i++)
 		ov5645->supplies[i].supply = ov5645_supply_name[i];
-- 
2.20.1