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  3. [PATCH v3 0/8] media: camss: Add support for C-PHY configuration on Qualcomm platforms
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[PATCH v3 8/8] media: qcom: camss: Account for C-PHY when calculating link frequency

David Heidelberg via B4 Relay posted 8 patches 3 weeks, 1 day ago
[PATCH v3 8/8] media: qcom: camss: Account for C-PHY when calculating link frequency
Posted by David Heidelberg via B4 Relay 3 weeks, 1 day ago 
From: David Heidelberg <david@ixit.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@linux.intel.com>
Signed-off-by: David Heidelberg <david@ixit.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        | 16 +++++++++++++---
 drivers/media/platform/qcom/camss/camss.h        |  2 +-
 4 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/drivers/media/platform/qcom/camss/camss-csid.c b/drivers/media/platform/qcom/camss/camss-csid.c
index b50b0cfe280c1..24f244d2959c9 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 08dd238e52799..1ea0d0ef354ff 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.phy_cfg == V4L2_MBUS_CSI2_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.phy_cfg == V4L2_MBUS_CSI2_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 ea0c8cf3cd806..556fedd92e065 100644
--- a/drivers/media/platform/qcom/camss/camss.c
+++ b/drivers/media/platform/qcom/camss/camss.c
@@ -32,6 +32,14 @@
 #define CAMSS_CLOCK_MARGIN_NUMERATOR 105
 #define CAMSS_CLOCK_MARGIN_DENOMINATOR 100
 
+/*
+ * C-PHY encodes data by 16/7 ~ 2.28 bits/symbol
+ * D-PHY doesn't encode data, thus 16/16 = 1 b/s
+ */
+#define CAMSS_COMMON_PHY_DIVIDENT 16
+#define CAMSS_CPHY_DIVISOR 7
+#define CAMSS_DPHY_DIVISOR 16
+
 static const struct parent_dev_ops vfe_parent_dev_ops;
 
 static const struct camss_subdev_resources csiphy_res_8x16[] = {
@@ -4280,20 +4288,22 @@ 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 ? CAMSS_CPHY_DIVISOR :
+						     CAMSS_DPHY_DIVISOR);
 
 	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, CAMSS_COMMON_PHY_DIVIDENT * bpp, div);
 }
 
 /*
diff --git a/drivers/media/platform/qcom/camss/camss.h b/drivers/media/platform/qcom/camss/camss.h
index 6d048414c919e..6bf7738837b89 100644
--- a/drivers/media/platform/qcom/camss/camss.h
+++ b/drivers/media/platform/qcom/camss/camss.h
@@ -163,7 +163,7 @@ 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
Re: [PATCH v3 8/8] media: qcom: camss: Account for C-PHY when calculating link frequency
Posted by Bryan O'Donoghue 3 weeks, 1 day ago 
On 17/01/2026 15:36, David Heidelberg via B4 Relay wrote:
> From: David Heidelberg <david@ixit.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@linux.intel.com>
> Signed-off-by: David Heidelberg <david@ixit.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        | 16 +++++++++++++---
>   drivers/media/platform/qcom/camss/camss.h        |  2 +-
>   4 files changed, 19 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/media/platform/qcom/camss/camss-csid.c b/drivers/media/platform/qcom/camss/camss-csid.c
> index b50b0cfe280c1..24f244d2959c9 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);

Just pass &csid->phy ..
>   	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 08dd238e52799..1ea0d0ef354ff 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.phy_cfg == V4L2_MBUS_CSI2_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);

CPHY shouldn't be a boolean special case - you have a use-case for the 
containing structure, so pass that instead.
>   	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.phy_cfg == V4L2_MBUS_CSI2_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 ea0c8cf3cd806..556fedd92e065 100644
> --- a/drivers/media/platform/qcom/camss/camss.c
> +++ b/drivers/media/platform/qcom/camss/camss.c
> @@ -32,6 +32,14 @@
>   #define CAMSS_CLOCK_MARGIN_NUMERATOR 105
>   #define CAMSS_CLOCK_MARGIN_DENOMINATOR 100
>   
> +/*
> + * C-PHY encodes data by 16/7 ~ 2.28 bits/symbol
> + * D-PHY doesn't encode data, thus 16/16 = 1 b/s
> + */
> +#define CAMSS_COMMON_PHY_DIVIDENT 16
> +#define CAMSS_CPHY_DIVISOR 7
> +#define CAMSS_DPHY_DIVISOR 16
> +
>   static const struct parent_dev_ops vfe_parent_dev_ops;
>   
>   static const struct camss_subdev_resources csiphy_res_8x16[] = {
> @@ -4280,20 +4288,22 @@ 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 ? CAMSS_CPHY_DIVISOR :
> +						     CAMSS_DPHY_DIVISOR);
>   
>   	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, CAMSS_COMMON_PHY_DIVIDENT * bpp, div);
>   }
>   
>   /*
> diff --git a/drivers/media/platform/qcom/camss/camss.h b/drivers/media/platform/qcom/camss/camss.h
> index 6d048414c919e..6bf7738837b89 100644
> --- a/drivers/media/platform/qcom/camss/camss.h
> +++ b/drivers/media/platform/qcom/camss/camss.h
> @@ -163,7 +163,7 @@ 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);
>
Re: [PATCH v3 8/8] media: qcom: camss: Account for C-PHY when calculating link frequency
Posted by kernel test robot 3 weeks, 1 day ago 
Hi David,

kernel test robot noticed the following build warnings:

[auto build test WARNING on 46fe65a2c28ecf5df1a7475aba1f08ccf4c0ac1b]

url:    https://github.com/intel-lab-lkp/linux/commits/David-Heidelberg-via-B4-Relay/media-qcom-camss-csiphy-Introduce-PHY-configuration/20260117-234024
base:   46fe65a2c28ecf5df1a7475aba1f08ccf4c0ac1b
patch link:    https://lore.kernel.org/r/20260117-qcom-cphy-v3-8-8ce76a06f7db%40ixit.cz
patch subject: [PATCH v3 8/8] media: qcom: camss: Account for C-PHY when calculating link frequency
config: m68k-allmodconfig (https://download.01.org/0day-ci/archive/20260118/202601180402.n3SE2vPM-lkp@intel.com/config)
compiler: m68k-linux-gcc (GCC) 15.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260118/202601180402.n3SE2vPM-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202601180402.n3SE2vPM-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> Warning: drivers/media/platform/qcom/camss/camss.c:4296 function parameter 'cphy' not described in 'camss_get_link_freq'
>> Warning: drivers/media/platform/qcom/camss/camss.c:4296 function parameter 'cphy' not described in 'camss_get_link_freq'

-- 
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki

Patchew 2.1-devel-b67e4c2

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