[PATCH v3 3/3] media: i2c: imx471: Derive pixel rate from PLL configuration

[Kate Hsuan <hpa@redhat.com>]

Derive the pixel rate from the sensor's external clock frequency and
active PLL settings.

The discussion of pixel rate can be found at the URL
Link: https://lore.kernel.org/linux-media/CAEth8oHj1Jon9m_4aFzRGoKcdopUMym+MyV0JxTo6F+AUFOLoQ@mail.gmail.com/

Signed-off-by: Kate Hsuan <hpa@redhat.com>
---
 drivers/media/i2c/imx471.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/media/i2c/imx471.c b/drivers/media/i2c/imx471.c
index b469fef7eef9..fc6a12943991 100644
--- a/drivers/media/i2c/imx471.c
+++ b/drivers/media/i2c/imx471.c
@@ -65,7 +65,7 @@
 
 /* default link frequency and external clock */
 #define IMX471_LINK_FREQ_DEFAULT		200000000LL
-#define IMX471_EXT_CLK				19200000
+#define IMX471_EXT_CLK				19200000LL
 
 /* PLL */
 #define IMX471_REG_VTPXCK_DIV			CCI_REG16(0x0300)
@@ -704,9 +704,15 @@ static int imx471_init_controls(struct imx471 *sensor)
 					   ARRAY_SIZE(link_freq_menu_items) - 1,
 					   0,
 					   link_freq_menu_items);
-
-	/* pixel_rate = link_freq * 2 * nr_of_lanes / bits_per_sample */
-	pixel_rate = div_u64(IMX471_LINK_FREQ_DEFAULT * 2 * 4, 10);
+	/*
+	 * The sensor runs in the dual mode so the pixel rate is defined as
+	 * follows:
+	 * (ext_freq * IVT_PLL_MPY * num_of_vt_lanes) /
+	 * (VT_PREPLLCK_DIV * IVT_SYCK_DIV * IVT_PXCK_DIV)
+	 */
+	pixel_rate = (IMX471_EXT_CLK * IMX471_PLL_VT_MPY * 4) /
+		     (IMX471_PREPLLCK_VT_DIV * IMX471_VTSYCK_DIV *
+		      IMX471_VTPXCK_DIV);
 
 	v4l2_ctrl_new_std(ctrl_hdlr, &imx471_ctrl_ops,
 			  V4L2_CID_PIXEL_RATE, pixel_rate,
-- 
2.55.0