[PATCH WIP v5 8/9] media: qcom: camss: Account for C-PHY when calculating link frequency
From: David Heidelberg via B4 Relay
Date: Sun May 31 2026 - 09:13:36 EST
From: David Heidelberg <david@xxxxxxx>
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@xxxxxxxxxxxxxxx>
Acked-by: Cory Keitz <ckeitz@xxxxxxxxxx>
Tested-by: Cory Keitz <ckeitz@xxxxxxxxxx>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@xxxxxxxxxx>
Signed-off-by: David Heidelberg <david@xxxxxxx>
---
drivers/media/platform/qcom/camss/camss-csid.c | 7 +++++--
drivers/media/platform/qcom/camss/camss-csiphy.c | 6 ++----
drivers/media/platform/qcom/camss/camss.c | 18 +++++++++++++++---
drivers/media/platform/qcom/camss/camss.h | 2 +-
4 files changed, 23 insertions(+), 10 deletions(-)
diff --git a/drivers/media/platform/qcom/camss/camss-csid.c b/drivers/media/platform/qcom/camss/camss-csid.c
index 8d5c872f84ed5..594f280a455ed 100644
--- a/drivers/media/platform/qcom/camss/camss-csid.c
+++ b/drivers/media/platform/qcom/camss/camss-csid.c
@@ -534,25 +534,28 @@ 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;
+ struct csiphy_device *csiphy = &csid->camss->csiphy[csid->phy.csiphy_id];
+ struct csiphy_lanes_cfg *lane_cfg = &csiphy->cfg.csi2->lane_cfg;
const struct csid_format_info *fmt;
+
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, lane_cfg);
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 ec0dc9d31b585..cd16743858d6a 100644
--- a/drivers/media/platform/qcom/camss/camss-csiphy.c
+++ b/drivers/media/platform/qcom/camss/camss-csiphy.c
@@ -138,19 +138,18 @@ 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;
- link_freq = camss_get_link_freq(&csiphy->subdev.entity, bpp, num_lanes);
+ link_freq = camss_get_link_freq(&csiphy->subdev.entity, bpp, &csiphy->cfg.csi2->lane_cfg);
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;
@@ -265,20 +264,19 @@ 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;
const struct csiphy_hw_ops *ops = csiphy->res->hw_ops;
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;
u8 val;
- link_freq = camss_get_link_freq(&csiphy->subdev.entity, bpp, num_lanes);
+ link_freq = camss_get_link_freq(&csiphy->subdev.entity, bpp, &csiphy->cfg.csi2->lane_cfg);
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..db4e14a84a95f 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 },
@@ -4618,30 +4626,34 @@ struct media_pad *camss_find_sensor_pad(struct media_entity *entity)
return pad;
}
}
/**
* 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
+ * @lane_cfg: CSI2 lane configuration
*
* 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)
+ struct csiphy_lanes_cfg *lane_cfg)
{
struct media_pad *sensor_pad;
+ u8 num_lanes = lane_cfg->num_data;
+ bool cphy = lane_cfg->phy_cfg == V4L2_MBUS_CSI2_CPHY;
+ unsigned int div = num_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..d65a9b62f7e66 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);
+ struct csiphy_lanes_cfg *lane_cfg);
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