[PATCH v2 3/9] media: i2c: ov7251: Report the pixel array rate for both link frequencies

[Antoine Pichot <antoine.pichot@gmail.com>]

pixel_rates[] gives V4L2_CID_PIXEL_RATE 48 MHz for the 240 MHz link and
63.84 MHz for the 319.2 MHz link, which is the CSI-2 bus rate of each
link (one lane, 10 bits per pixel). The control is the pixel array rate,
and Documentation/driver-api/media/tx-rx.rst says the bus rate "is not
the same thing as the pixel rate on the camera sensor's pixel array
which is indicated by the V4L2_CID_PIXEL_RATE control".

The pixel array runs from PLL2's 48 MHz system clock at both link
frequencies: the PLL2 registers are the same in both tables, and the
measured frame rate is 48000000 / (928 x VTS) with either link. On a
Surface Book 2 at 319.2 MHz, VTS 1724 gives 30.0 fps; 63.84 MHz would
give 39.9 fps. A Surface Pro 7+ measures 30.01, 60.16 and 90.45 fps at
VTS 1724, 860 and 572, the same 48 MHz. Dave Stevenson saw the same on
a Raspberry Pi with a 24 MHz clock, where libcamera asked for 100 fps
and got 75, the ratio of the two rates.

Report 48 MHz for both link frequencies and drop the table.

Fixes: ed9566ce1946 ("media: i2c: Add support for new frequencies to ov7251")
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/linux-media/CAPY8ntBFJJPg3y46gC=bNq_55QifC7mKmeq8+pAEDVN42fGUXw@mail.gmail.com/
Signed-off-by: Antoine Pichot <antoine.pichot@gmail.com>
---
 drivers/media/i2c/ov7251.c | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/drivers/media/i2c/ov7251.c b/drivers/media/i2c/ov7251.c
index 1f30a01c85b3..2db6c28a6e34 100644
--- a/drivers/media/i2c/ov7251.c
+++ b/drivers/media/i2c/ov7251.c
@@ -22,6 +22,9 @@
 #include <media/v4l2-fwnode.h>
 #include <media/v4l2-subdev.h>
 
+/* PLL2 sys_clk: the pixel array clock at both link frequencies */
+#define OV7251_PIXEL_CLOCK 48000000
+
 #define OV7251_SC_MODE_SELECT		0x0100
 #define OV7251_SC_MODE_SELECT_SW_STANDBY	0x0
 #define OV7251_SC_MODE_SELECT_STREAMING		0x1
@@ -633,11 +636,6 @@ static const s64 link_freq[] = {
 	[OV7251_LINK_FREQ_319_2_MHZ] = 319200000,
 };
 
-static const s64 pixel_rates[] = {
-	[OV7251_LINK_FREQ_240_MHZ] = 48000000,
-	[OV7251_LINK_FREQ_319_2_MHZ] = 63840000,
-};
-
 static const struct ov7251_mode_info ov7251_mode_info_data[] = {
 	{
 		.width = 640,
@@ -1567,7 +1565,6 @@ static int ov7251_detect_chip(struct ov7251 *ov7251)
 static int ov7251_init_ctrls(struct ov7251 *ov7251)
 {
 	int vblank_max, vblank_def;
-	s64 pixel_rate;
 	int hblank;
 
 	v4l2_ctrl_handler_init(&ov7251->ctrls, 7);
@@ -1586,12 +1583,12 @@ static int ov7251_init_ctrls(struct ov7251 *ov7251)
 				     ARRAY_SIZE(ov7251_test_pattern_menu) - 1,
 				     0, 0, ov7251_test_pattern_menu);
 
-	pixel_rate = pixel_rates[ov7251->link_freq_idx];
 	ov7251->pixel_clock = v4l2_ctrl_new_std(&ov7251->ctrls,
 						&ov7251_ctrl_ops,
 						V4L2_CID_PIXEL_RATE,
-						pixel_rate, INT_MAX,
-						pixel_rate, pixel_rate);
+						OV7251_PIXEL_CLOCK, INT_MAX,
+						OV7251_PIXEL_CLOCK,
+						OV7251_PIXEL_CLOCK);
 	ov7251->link_freq = v4l2_ctrl_new_int_menu(&ov7251->ctrls,
 						   &ov7251_ctrl_ops,
 						   V4L2_CID_LINK_FREQ,
-- 
2.56.0