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Message-Id: <20251204-qcom-cphy-v2-8-6b35ef8b071e@ixit.cz>
Date: Thu, 04 Dec 2025 17:32:42 +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>,
Kieran Bingham <kbingham@...nel.org>,
Sakari Ailus <sakari.ailus@...ux.intel.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>
Subject: [PATCH WIP v2 8/8] 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 | 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 d9026fd829d61..437f51dc86f9f 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..bac3a9fa3be50 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 414646760ae6b..6333f5dd73b53 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[] = {
@@ -3912,20 +3920,22 @@ 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 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
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