[media] media: ov7670: add possibility to bypass pll for ov7675

For a frame rate of 30 fps a pixclk of 24MHz is needed. For those
cases where the ov7670 has a clean 24MHz input (xvclk) the PLL
can be bypassed.
This will result in a value of clkrc of 1, which means that in practice
pixclk = xvclk (input clock)

Acked-by: Jonathan Corbet <[e-mail]>
Signed-off-by: Javier Martin <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/i2c/ov7670.c

···
 	int clock_speed;		/* External clock speed (MHz) */
 	u8 clkrc;			/* Clock divider value */
 	bool use_smbus;			/* Use smbus I/O instead of I2C */
+	bool pll_bypass;
 	const struct ov7670_devtype *devtype; /* Device specifics */
 };
 
···
 {
 	struct ov7670_info *info = to_state(sd);
 	u32 clkrc = info->clkrc;
-	u32 pll_factor = PLL_FACTOR;
+	int pll_factor;
+
+	if (info->pll_bypass)
+		pll_factor = 1;
+	else
+		pll_factor = PLL_FACTOR;
 
 	clkrc++;
 	if (info->fmt->mbus_code == V4L2_MBUS_FMT_SBGGR8_1X8)
···
 {
 	struct ov7670_info *info = to_state(sd);
 	u32 clkrc;
-	u32 pll_factor = PLL_FACTOR;
+	int pll_factor;
 	int ret;
 
 	/*
···
 	 * pixclk = clock_speed / (clkrc + 1) * PLLfactor
 	 *
 	 */
+	if (info->pll_bypass) {
+		pll_factor = 1;
+		ret = ov7670_write(sd, REG_DBLV, DBLV_BYPASS);
+	} else {
+		pll_factor = PLL_FACTOR;
+		ret = ov7670_write(sd, REG_DBLV, DBLV_X4);
+	}
+	if (ret < 0)
+		return ret;
+
 	if (tpf->numerator == 0 || tpf->denominator == 0) {
 		clkrc = 0;
 	} else {
···
 	ret = ov7670_write(sd, REG_CLKRC, info->clkrc);
 	if (ret < 0)
 		return ret;
+
 	return ov7670_write(sd, REG_DBLV, DBLV_X4);
 }
 
···
 
 		if (config->clock_speed)
 			info->clock_speed = config->clock_speed;
+
+		/*
+		 * It should be allowed for ov7670 too when it is migrated to
+		 * the new frame rate formula.
+		 */
+		if (config->pll_bypass && id->driver_data != MODEL_OV7670)
+			info->pll_bypass = true;
 	}
 
 	/* Make sure it's an ov7670 */

include/media/ov7670.h

···
 	int min_height;			/* Filter out smaller sizes */
 	int clock_speed;		/* External clock speed (MHz) */
 	bool use_smbus;			/* Use smbus I/O instead of I2C */
+	bool pll_bypass;		/* Choose whether to bypass the PLL */
 };
 
 #endif