linux-kernel - [PATCH 1/6] media: ov6650: Fix stored frame interval not in sync with hardware

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Message-Id: <20191013125050.4153-2-jmkrzyszt@gmail.com>
Date:   Sun, 13 Oct 2019 14:50:45 +0200
From:   Janusz Krzysztofik <jmkrzyszt@...il.com>
To:     Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc:     Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Janusz Krzysztofik <jmkrzyszt@...il.com>
Subject: [PATCH 1/6] media: ov6650: Fix stored frame interval not in sync with hardware

The driver stores a frame interval value supposed to be in line with
hardware state in a device private structure.  Since the driver initial
submission, the respective field of the structure has never been
initialised on device probe.  Moreover, if updated from
.s_frame_interval(), a new value is stored before it is applied on
hardware.  If an error occurs during device update, the stored value
may no longer reflect hardware state and consecutive calls to
.g_frame_interval() may return incorrect information.

Assuming a failed update of the device means its actual state hasn't
changed, update the frame interval field of the device private
structure with a new value only after it is successfully applied on
hardware so it always reflects actual hardware state to the extent
possible.  Also, initialise the field with hardware default frame
interval on device probe.

Signed-off-by: Janusz Krzysztofik <jmkrzyszt@...il.com>
---
 drivers/media/i2c/ov6650.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/drivers/media/i2c/ov6650.c b/drivers/media/i2c/ov6650.c
index 16887049f0cd..f60aeb1f7813 100644
--- a/drivers/media/i2c/ov6650.c
+++ b/drivers/media/i2c/ov6650.c
@@ -130,6 +130,7 @@
 #define CLKRC_24MHz		0xc0
 #define CLKRC_DIV_MASK		0x3f
 #define GET_CLKRC_DIV(x)	(((x) & CLKRC_DIV_MASK) + 1)
+#define DEF_CLKRC		0x00
 
 #define COMA_RESET		BIT(7)
 #define COMA_QCIF		BIT(5)
@@ -783,19 +784,17 @@ static int ov6650_s_frame_interval(struct v4l2_subdev *sd,
 	else if (div > GET_CLKRC_DIV(CLKRC_DIV_MASK))
 		div = GET_CLKRC_DIV(CLKRC_DIV_MASK);
 
-	/*
-	 * Keep result to be used as tpf limit
-	 * for subsequent clock divider calculations
-	 */
-	priv->tpf.numerator = div;
-	priv->tpf.denominator = FRAME_RATE_MAX;
+	tpf->numerator = div;
+	tpf->denominator = FRAME_RATE_MAX;
 
-	clkrc = to_clkrc(&priv->tpf, priv->pclk_limit, priv->pclk_max);
+	clkrc = to_clkrc(tpf, priv->pclk_limit, priv->pclk_max);
 
 	ret = ov6650_reg_rmw(client, REG_CLKRC, clkrc, CLKRC_DIV_MASK);
 	if (!ret) {
-		tpf->numerator = GET_CLKRC_DIV(clkrc);
-		tpf->denominator = FRAME_RATE_MAX;
+		priv->tpf.numerator = GET_CLKRC_DIV(clkrc);
+		priv->tpf.denominator = FRAME_RATE_MAX;
+
+		*tpf = priv->tpf;
 	}
 
 	return ret;
@@ -1038,6 +1037,10 @@ static int ov6650_probe(struct i2c_client *client,
 	priv->rect.width  = W_CIF;
 	priv->rect.height = H_CIF;
 
+	/* Hardware default frame interval */
+	priv->tpf.numerator   = GET_CLKRC_DIV(DEF_CLKRC);
+	priv->tpf.denominator = FRAME_RATE_MAX;
+
 	priv->subdev.internal_ops = &ov6650_internal_ops;
 
 	ret = v4l2_async_register_subdev(&priv->subdev);
-- 
2.21.0