[PATCH v4 10/15] media: atomisp: derive CSI-2 timing from sensor link frequency

[Maurizio Casciano]

The ISP2401 CSI-2 receiver timing depends on the sensor link frequency.
Query it through v4l2_get_link_freq() instead of reading a 32-bit
control value directly.

Keep the frequency as s64 throughout the calculation so valid link
frequencies do not require an arbitrary S32_MAX limit. Fall back to the
existing default timings when the frequency query fails.

Link: https://lore.kernel.org/linux-media/apFzAc5XfV9gQpXS@kekkonen.localdomain/
Signed-off-by: Maurizio Casciano <mauriziocasciano7@xxxxxxxxx>
Assisted-by: Codex:gpt-5.6-sol sparse
---
 .../staging/media/atomisp/pci/atomisp_csi2.c  | 20 ++++++++++++-------
 1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/drivers/staging/media/atomisp/pci/atomisp_csi2.c b/drivers/staging/media/atomisp/pci/atomisp_csi2.c
index 95b9113d75e9..6c17b37350f6 100644
--- a/drivers/staging/media/atomisp/pci/atomisp_csi2.c
+++ b/drivers/staging/media/atomisp/pci/atomisp_csi2.c
@@ -5,6 +5,7 @@
  * Copyright (c) 2010 Intel Corporation. All Rights Reserved.
  */
 
+#include <media/v4l2-common.h>
 #include <media/v4l2-event.h>
 #include <media/v4l2-mediabus.h>
 #include "atomisp_cmd.h"
@@ -209,7 +210,7 @@ int atomisp_mipi_csi2_register_entities(struct atomisp_mipi_csi2_device *csi2,
 static const int LIMIT_SHIFT = 6;	/* Limit numeric range into 31 bits */
 
 static int
-atomisp_csi2_configure_calc(const short int coeffs[2], int mipi_freq, int def)
+atomisp_csi2_configure_calc(const short int coeffs[2], s64 mipi_freq, int def)
 {
 	/* Delay counter accuracy, 1/0.0625 for ANN/CHT, 1/0.125 for BXT */
 	static const int accinv = 16;		/* 1 / COUNT_ACC */
@@ -288,18 +289,18 @@ static void atomisp_csi2_configure_isp2401(struct atomisp_sub_device *asd)
 	int dat_termen;
 	int dat_settle;
 
-	struct v4l2_control ctrl;
 	struct atomisp_device *isp = asd->isp;
-	int mipi_freq = 0;
+	struct v4l2_subdev *sensor;
+	s64 mipi_freq;
 	enum atomisp_camera_port port;
 	int n;
 
 	port = isp->inputs[asd->input_curr].port;
 
-	ctrl.id = V4L2_CID_LINK_FREQ;
-	if (v4l2_g_ctrl
-	    (isp->inputs[asd->input_curr].sensor->ctrl_handler, &ctrl) == 0)
-		mipi_freq = ctrl.value;
+	sensor = isp->inputs[asd->input_curr].sensor;
+	mipi_freq = v4l2_get_link_freq(&sensor->entity.pads[0], 0, 0);
+	if (mipi_freq < 0)
+		mipi_freq = 0;
 
 	clk_termen = atomisp_csi2_configure_calc(coeff_clk_termen, mipi_freq,
 						 TERMEN_DEFAULT);
@@ -310,6 +311,11 @@ static void atomisp_csi2_configure_isp2401(struct atomisp_sub_device *asd)
 	dat_settle = atomisp_csi2_configure_calc(coeff_dat_settle, mipi_freq,
 						 SETTLE_DEFAULT);
 
+	dev_dbg(isp->dev,
+		"CSI port %u link frequency %lld Hz, clk timing %d/%d, data timing %d/%d\n",
+		port, mipi_freq, clk_termen, clk_settle,
+		dat_termen, dat_settle);
+
 	for (n = 0; n < csi2_port_lanes[port] + 1; n++) {
 		hrt_address base = csi2_port_base[port] + csi2_lane_base[n];
 
-- 
2.53.0