On Wed, Jul 29, 2026 at 10:20:03PM +0200, David Heidelberg wrote:
> 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 <[email protected]>
> Link: https://docs.kernel.org/driver-api/media/tx-rx.html#pixel-rate
> Signed-off-by: David Heidelberg <[email protected]>
> ---
> drivers/media/platform/qcom/camss/camss-csid.c | 6 ++++--
> drivers/media/platform/qcom/camss/camss-csiphy.c | 6 ++++--
> drivers/media/platform/qcom/camss/camss.c | 15 +++++++++++++--
> drivers/media/platform/qcom/camss/camss.h | 2 +-
> 4 files changed, 22 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/media/platform/qcom/camss/camss-csid.c
> b/drivers/media/platform/qcom/camss/camss-csid.c
> index bcc34ac9dd212..c8cb6f1a3d3bc 100644
> --- a/drivers/media/platform/qcom/camss/camss-csid.c
> +++ b/drivers/media/platform/qcom/camss/camss-csid.c
> @@ -535,24 +535,26 @@ const struct csid_format_info *csid_get_fmt_entry(const
> struct csid_format_info
> /*
> * csid_set_clock_rates - Calculate and set clock rates on CSID module
> * @csiphy: CSID device
> */
> static int csid_set_clock_rates(struct csid_device *csid)
> {
> struct device *dev = csid->camss->dev;
> const struct csid_format_info *fmt;
> + const bool cphy = (csid->phy.phy_sel == CSID_PHY_SEL_CPHY);
> +
> s64 link_freq;
> int i, j;
> int ret;
>
> 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);
> +
> + link_freq = camss_get_link_freq(&csid->subdev.entity, fmt->bpp,
> csid->phy.lane_cnt, cphy);
> if (link_freq < 0)
> link_freq = 0;
>
> for (i = 0; i < csid->nclocks; i++) {
> struct camss_clock *clock = &csid->clock[i];
>
> if (!strcmp(clock->name, "csi0") ||
> !strcmp(clock->name, "csi1") ||
> diff --git a/drivers/media/platform/qcom/camss/camss-csiphy.c
> b/drivers/media/platform/qcom/camss/camss-csiphy.c
> index 539ac4888b608..a136cd27880a6 100644
> --- a/drivers/media/platform/qcom/camss/camss-csiphy.c
> +++ b/drivers/media/platform/qcom/camss/camss-csiphy.c
> @@ -139,18 +139,19 @@ static int csiphy_set_clock_rates(struct csiphy_device
> *csiphy)
> struct device *dev = csiphy->camss->dev;
> s64 link_freq;
> int i, j;
> int ret;
>
> 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;
> + const 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;
>
> for (i = 0; i < csiphy->nclocks; i++) {
> struct camss_clock *clock = &csiphy->clock[i];
>
> if (csiphy->rate_set[i]) {
> u64 min_rate = link_freq / 4;
> @@ -265,19 +266,20 @@ static int csiphy_set_power(struct v4l2_subdev *sd, int
> on)
> static int csiphy_stream_on(struct csiphy_device *csiphy)
> {
> struct csiphy_config *cfg = &csiphy->cfg;
> s64 link_freq;
> u8 lane_mask = csiphy->res->hw_ops->get_lane_mask(&cfg->csi2->lane_cfg);
> 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;
> + const 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,
> "Cannot get CSI2 transmitter's link frequency\n");
> return -EINVAL;
> }
>
> if (csiphy->base_clk_mux) {
> diff --git a/drivers/media/platform/qcom/camss/camss.c
> b/drivers/media/platform/qcom/camss/camss.c
> index 072c428e25166..66171069057f8 100644
> --- a/drivers/media/platform/qcom/camss/camss.c
> +++ b/drivers/media/platform/qcom/camss/camss.c
> @@ -27,16 +27,24 @@
> #include <media/v4l2-mc.h>
> #include <media/v4l2-fwnode.h>
>
> #include "camss.h"
>
> #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[] = {
> /* CSIPHY0 */
> {
> .regulators = {},
> .clock = { "top_ahb", "ispif_ahb", "ahb", "csiphy0_timer" },
> .clock_rate = { { 0 },
> @@ -4619,29 +4627,32 @@ 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
> + * @cphy: If C-PHY encoding is used.
> *
> * 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 lanes, const bool cphy)
you change this function argument, can you direct pass down csiphy instead
entity
so move
const bool cphy = (csiphy->cfg.csi2->lane_cfg.phy_cfg == V4L2_MBUS_CSI2_CPHY);
into this help function,
to avoid dupicate such logic everywhere.
Frank
> {
> struct media_pad *sensor_pad;
> + unsigned int div = 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);
> }
>
> /*
> * camss_get_pixel_clock - Get pixel clock rate from sensor
> * @entity: Media entity in the current pipeline
> * @pixel_clock: Received pixel clock value
> *
> * Return 0 on success or a negative error code otherwise
> diff --git a/drivers/media/platform/qcom/camss/camss.h
> b/drivers/media/platform/qcom/camss/camss.h
> index 93d691c8ac63b..12b14ba8fcec3 100644
> --- a/drivers/media/platform/qcom/camss/camss.h
> +++ b/drivers/media/platform/qcom/camss/camss.h
> @@ -164,17 +164,17 @@ struct parent_dev_ops {
> };
>
> void camss_add_clock_margin(u64 *rate);
> int camss_enable_clocks(int nclocks, struct camss_clock *clock,
> struct device *dev);
> 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, const 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);
> int camss_vfe_get(struct camss *camss, int id);
> void camss_vfe_put(struct camss *camss, int id);
> void camss_delete(struct camss *camss);
> void camss_buf_done(struct camss *camss, int hw_id, int port_id);
> void camss_reg_update(struct camss *camss, int hw_id,
>
> --
> 2.53.0
>
