linux-kernel - [PATCH 1/2] media: ov5675: Derive delay cycles from the clock rate reported

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Message-Id: <20240711-linux-next-ov5675-v1-1-69e9b6c62c16@linaro.org>
Date: Thu, 11 Jul 2024 11:20:01 +0100
From: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
To: Sakari Ailus <sakari.ailus@...ux.intel.com>, 
 Mauro Carvalho Chehab <mchehab@...nel.org>, 
 Quentin Schulz <quentin.schulz@...obroma-systems.com>, 
 Jacopo Mondi <jacopo@...ndi.org>
Cc: Johan Hovold <johan@...nel.org>, 
 Kieran Bingham <kieran.bingham@...asonboard.com>, 
 linux-media@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Bryan O'Donoghue <bryan.odonoghue@...aro.org>
Subject: [PATCH 1/2] media: ov5675: Derive delay cycles from the clock rate
 reported

The ov5675 driver expresses its reset delays in terms of XVCLK cycles as
per the ov5675 specification. XVCLK can be anything in the range of 6 MHz
to 24 MHz inclusive.

Upstream we use 19.2 MHz however, since the delays are calculated in terms
of clock cycles as opposed to fixed intervals it makes sense to facilitate
any potential clock we might support.

Do so by reading the XVCLK rate and using the returned rate instead of
operating from a static definition.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
---
 drivers/media/i2c/ov5675.c | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/drivers/media/i2c/ov5675.c b/drivers/media/i2c/ov5675.c
index 3641911bc73f..92bd35133a5d 100644
--- a/drivers/media/i2c/ov5675.c
+++ b/drivers/media/i2c/ov5675.c
@@ -497,6 +497,7 @@ struct ov5675 {
 	struct media_pad pad;
 	struct v4l2_ctrl_handler ctrl_handler;
 	struct clk *xvclk;
+	u32 xvclk_rate;
 	struct gpio_desc *reset_gpio;
 	struct regulator_bulk_data supplies[OV5675_NUM_SUPPLIES];
 
@@ -973,10 +974,11 @@ static int ov5675_set_stream(struct v4l2_subdev *sd, int enable)
 static int ov5675_power_off(struct device *dev)
 {
 	/* 512 xvclk cycles after the last SCCB transation or MIPI frame end */
-	u32 delay_us = DIV_ROUND_UP(512, OV5675_XVCLK_19_2 / 1000 / 1000);
 	struct v4l2_subdev *sd = dev_get_drvdata(dev);
 	struct ov5675 *ov5675 = to_ov5675(sd);
+	u32 delay_us;
 
+	delay_us = DIV_ROUND_UP(512, ov5675->xvclk_rate / 1000 / 1000);
 	usleep_range(delay_us, delay_us * 2);
 
 	clk_disable_unprepare(ov5675->xvclk);
@@ -988,11 +990,13 @@ static int ov5675_power_off(struct device *dev)
 
 static int ov5675_power_on(struct device *dev)
 {
-	u32 delay_us = DIV_ROUND_UP(8192, OV5675_XVCLK_19_2 / 1000 / 1000);
 	struct v4l2_subdev *sd = dev_get_drvdata(dev);
 	struct ov5675 *ov5675 = to_ov5675(sd);
+	u32 delay_us;
 	int ret;
 
+	delay_us = DIV_ROUND_UP(8192, ov5675->xvclk_rate / 1000 / 1000);
+
 	ret = clk_prepare_enable(ov5675->xvclk);
 	if (ret < 0) {
 		dev_err(dev, "failed to enable xvclk: %d\n", ret);
@@ -1178,7 +1182,6 @@ static int ov5675_get_hwcfg(struct ov5675 *ov5675, struct device *dev)
 	struct v4l2_fwnode_endpoint bus_cfg = {
 		.bus_type = V4L2_MBUS_CSI2_DPHY
 	};
-	u32 xvclk_rate;
 	int ret;
 	unsigned int i, j;
 
@@ -1192,10 +1195,10 @@ static int ov5675_get_hwcfg(struct ov5675 *ov5675, struct device *dev)
 				     PTR_ERR(ov5675->xvclk));
 
 	if (ov5675->xvclk) {
-		xvclk_rate = clk_get_rate(ov5675->xvclk);
+		ov5675->xvclk_rate = clk_get_rate(ov5675->xvclk);
 	} else {
 		ret = fwnode_property_read_u32(fwnode, "clock-frequency",
-					       &xvclk_rate);
+					       &ov5675->xvclk_rate);
 
 		if (ret) {
 			dev_err(dev, "can't get clock frequency");
@@ -1203,9 +1206,9 @@ static int ov5675_get_hwcfg(struct ov5675 *ov5675, struct device *dev)
 		}
 	}
 
-	if (xvclk_rate != OV5675_XVCLK_19_2) {
+	if (ov5675->xvclk_rate != OV5675_XVCLK_19_2) {
 		dev_err(dev, "external clock rate %u is unsupported",
-			xvclk_rate);
+			ov5675->xvclk_rate);
 		return -EINVAL;
 	}
 

-- 
2.45.2