linux-kernel - [PATCH RFC 7/8] media: qcom: camss: Account for C-PHY when calculating link frequency

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Message-Id: <20251109-qcom-cphy-v1-7-165f7e79b0e1@ixit.cz>
Date: Sun, 09 Nov 2025 10:39:50 +0100
From: David Heidelberg via B4 Relay <devnull+david.ixit.cz@...nel.org>
To: Robert Foss <rfoss@...nel.org>, Todor Tomov <todor.too@...il.com>, 
 Bryan O'Donoghue <bryan.odonoghue@...aro.org>, 
 Vladimir Zapolskiy <vladimir.zapolskiy@...aro.org>, 
 Mauro Carvalho Chehab <mchehab@...nel.org>, 
 Luca Weiss <luca.weiss@...rphone.com>, Petr Hodina <phodina@...tonmail.com>, 
 Casey Connolly <casey.connolly@...aro.org>, "Dr. Git" <drgitx@...il.com>
Cc: Joel Selvaraj <foss@...lselvaraj.com>, linux-media@...r.kernel.org, 
 linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org, 
 phone-devel@...r.kernel.org, David Heidelberg <david@...t.cz>, 
 Sakari Ailus <sakari.ailus@...ux.intel.com>
Subject: [PATCH RFC 7/8] media: qcom: camss: Account for C-PHY when
 calculating link frequency

From: David Heidelberg <david@...t.cz>

Ensure that the link frequency divider correctly accounts for C-PHY
operation. The divider differs between D-PHY and C-PHY, as described
in the MIPI CSI-2 specification.

For more details, see:
https://docs.kernel.org/driver-api/media/tx-rx.html#pixel-rate

Suggested-by: Sakari Ailus <sakari.ailus@...ux.intel.com>
Signed-off-by: David Heidelberg <david@...t.cz>
---
 drivers/media/platform/qcom/camss/camss-csid.c   | 2 +-
 drivers/media/platform/qcom/camss/camss-csiphy.c | 6 ++++--
 drivers/media/platform/qcom/camss/camss.c        | 7 ++++---
 drivers/media/platform/qcom/camss/camss.h        | 2 +-
 4 files changed, 10 insertions(+), 7 deletions(-)

diff --git a/drivers/media/platform/qcom/camss/camss-csid.c b/drivers/media/platform/qcom/camss/camss-csid.c
index 68adea33cc719..9fb5834b28e2b 100644
--- a/drivers/media/platform/qcom/camss/camss-csid.c
+++ b/drivers/media/platform/qcom/camss/camss-csid.c
@@ -545,7 +545,7 @@ static int csid_set_clock_rates(struct csid_device *csid)
 	fmt = csid_get_fmt_entry(csid->res->formats->formats, csid->res->formats->nformats,
 				 csid->fmt[MSM_CSIPHY_PAD_SINK].code);
 	link_freq = camss_get_link_freq(&csid->subdev.entity, fmt->bpp,
-					csid->phy.lane_cnt);
+					csid->phy.lane_cnt, csid->phy.cphy);
 	if (link_freq < 0)
 		link_freq = 0;
 
diff --git a/drivers/media/platform/qcom/camss/camss-csiphy.c b/drivers/media/platform/qcom/camss/camss-csiphy.c
index a734fb7dde0a4..61f2b2ac3f159 100644
--- a/drivers/media/platform/qcom/camss/camss-csiphy.c
+++ b/drivers/media/platform/qcom/camss/camss-csiphy.c
@@ -144,8 +144,9 @@ static int csiphy_set_clock_rates(struct csiphy_device *csiphy)
 	u8 bpp = csiphy_get_bpp(csiphy->res->formats->formats, csiphy->res->formats->nformats,
 				csiphy->fmt[MSM_CSIPHY_PAD_SINK].code);
 	u8 num_lanes = csiphy->cfg.csi2->lane_cfg.num_data;
+	bool cphy = csiphy->cfg.csi2->lane_cfg.cphy;
 
-	link_freq = camss_get_link_freq(&csiphy->subdev.entity, bpp, num_lanes);
+	link_freq = camss_get_link_freq(&csiphy->subdev.entity, bpp, num_lanes, cphy);
 	if (link_freq < 0)
 		link_freq  = 0;
 
@@ -270,9 +271,10 @@ static int csiphy_stream_on(struct csiphy_device *csiphy)
 	u8 bpp = csiphy_get_bpp(csiphy->res->formats->formats, csiphy->res->formats->nformats,
 				csiphy->fmt[MSM_CSIPHY_PAD_SINK].code);
 	u8 num_lanes = csiphy->cfg.csi2->lane_cfg.num_data;
+	bool cphy = csiphy->cfg.csi2->lane_cfg.cphy;
 	u8 val;
 
-	link_freq = camss_get_link_freq(&csiphy->subdev.entity, bpp, num_lanes);
+	link_freq = camss_get_link_freq(&csiphy->subdev.entity, bpp, num_lanes, cphy);
 
 	if (link_freq < 0) {
 		dev_err(csiphy->camss->dev,
diff --git a/drivers/media/platform/qcom/camss/camss.c b/drivers/media/platform/qcom/camss/camss.c
index 549780f3f948b..248aa6b21b5ad 100644
--- a/drivers/media/platform/qcom/camss/camss.c
+++ b/drivers/media/platform/qcom/camss/camss.c
@@ -3912,20 +3912,21 @@ struct media_pad *camss_find_sensor_pad(struct media_entity *entity)
  * camss_get_link_freq - Get link frequency from sensor
  * @entity: Media entity in the current pipeline
  * @bpp: Number of bits per pixel for the current format
- * @lanes: Number of lanes in the link to the sensor
+ * @nr_of_lanes: Number of lanes in the link to the sensor
  *
  * Return link frequency on success or a negative error code otherwise
  */
 s64 camss_get_link_freq(struct media_entity *entity, unsigned int bpp,
-			unsigned int lanes)
+			unsigned int nr_of_lanes, bool cphy)
 {
 	struct media_pad *sensor_pad;
+	unsigned int div = nr_of_lanes * 2 * (cphy ? 7 : 16);
 
 	sensor_pad = camss_find_sensor_pad(entity);
 	if (!sensor_pad)
 		return -ENODEV;
 
-	return v4l2_get_link_freq(sensor_pad, bpp, 2 * lanes);
+	return v4l2_get_link_freq(sensor_pad, 16 * bpp, div);
 }
 
 /*
diff --git a/drivers/media/platform/qcom/camss/camss.h b/drivers/media/platform/qcom/camss/camss.h
index 9d9a62640e25d..0ab908b0c037f 100644
--- a/drivers/media/platform/qcom/camss/camss.h
+++ b/drivers/media/platform/qcom/camss/camss.h
@@ -162,7 +162,7 @@ int camss_enable_clocks(int nclocks, struct camss_clock *clock,
 void camss_disable_clocks(int nclocks, struct camss_clock *clock);
 struct media_pad *camss_find_sensor_pad(struct media_entity *entity);
 s64 camss_get_link_freq(struct media_entity *entity, unsigned int bpp,
-			unsigned int lanes);
+			unsigned int lanes, bool cphy);
 int camss_get_pixel_clock(struct media_entity *entity, u64 *pixel_clock);
 int camss_pm_domain_on(struct camss *camss, int id);
 void camss_pm_domain_off(struct camss *camss, int id);

-- 
2.51.0