Re: [PATCH v2 2/3] media: camss: use v4l2_get_link_freq() to calculate the relevant clocks

From: Jacopo Mondi
Date: Thu Feb 18 2021 - 04:21:38 EST

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In reply to: Andrey Konovalov: "[PATCH v2 2/3] media: camss: use v4l2_get_link_freq() to calculate the relevant clocks"
Next in thread: Andrey Konovalov: "Re: [PATCH v2 2/3] media: camss: use v4l2_get_link_freq() to calculate the relevant clocks"
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Hi Andrey,

On Thu, Feb 18, 2021 at 01:11:33AM +0300, Andrey Konovalov wrote:
> There are places in the camss driver where camss_get_pixel_clock() is
> called to get the pixel rate (using V4L2_CID_PIXEL_RATE control) and to
> calculate the link frequency from it. There is a case when this would
> not work: when V4L2_CID_PIXEL_RATE gets the rate at which the pixels are
> read (sampled) from the sensor's pixel array, and this rate is different
> from the pixel transmission rate over the CSI link, the link frequency
> value can't be calculated from the pixel rate. One needs to use
> V4L2_CID_LINK_FREQ to get the link frequency in this case.
>
> Replace such calls to camss_get_pixel_clock() with calls to a wrapper
> around v4l2_get_link_freq(). v4l2_get_link_freq() tries V4L2_CID_LINK_FREQ
> first, and if it is not implemented by the camera sensor driver, falls
> back to V4L2_CID_PIXEL_RATE to calculate the link frequency value from.

That's nice

>
> Calls to camss_get_pixel_clock() from vfe_[check,set]_clock_rates()
> are left intact as it looks like this VFE clock does depend on the
> rate the pixel samples comes out of the camera sensor, not on the
> frequency at which the link between the sensor and the CSI receiver
> operates.

Out of curiosity, you have any idea why this happens ?

The patch looks good, fwiw given I don't know the platform:
Reviewed-by: Jacopo Mondi <jacopo@xxxxxxxxxx>

Thanks
j
>
> Signed-off-by: Andrey Konovalov <andrey.konovalov@xxxxxxxxxx>
> Acked-by: Robert Foss <robert.foss@xxxxxxxxxx>
> ---
> .../media/platform/qcom/camss/camss-csid.c | 20 +++++------
> .../qcom/camss/camss-csiphy-2ph-1-0.c | 22 ++++++------
> .../qcom/camss/camss-csiphy-3ph-1-0.c | 22 ++++++------
> .../media/platform/qcom/camss/camss-csiphy.c | 36 +++++++++----------
> .../media/platform/qcom/camss/camss-csiphy.h | 2 +-
> drivers/media/platform/qcom/camss/camss.c | 23 ++++++++++++
> drivers/media/platform/qcom/camss/camss.h | 2 ++
> 7 files changed, 71 insertions(+), 56 deletions(-)
>
> diff --git a/drivers/media/platform/qcom/camss/camss-csid.c b/drivers/media/platform/qcom/camss/camss-csid.c
> index be3fe76f3dc3..cff9759c9158 100644
> --- a/drivers/media/platform/qcom/camss/camss-csid.c
> +++ b/drivers/media/platform/qcom/camss/camss-csid.c
> @@ -462,13 +462,17 @@ static irqreturn_t csid_isr(int irq, void *dev)
> static int csid_set_clock_rates(struct csid_device *csid)
> {
> struct device *dev = csid->camss->dev;
> - u32 pixel_clock;
> + const struct csid_format *fmt;
> + s64 link_freq;
> int i, j;
> int ret;
>
> - ret = camss_get_pixel_clock(&csid->subdev.entity, &pixel_clock);
> - if (ret)
> - pixel_clock = 0;
> + fmt = csid_get_fmt_entry(csid->formats, csid->nformats,
> + csid->fmt[MSM_CSIPHY_PAD_SINK].code);
> + link_freq = camss_get_link_freq(&csid->subdev.entity, fmt->bpp,
> + csid->phy.lane_cnt);
> + if (link_freq < 0)
> + link_freq = 0;
>
> for (i = 0; i < csid->nclocks; i++) {
> struct camss_clock *clock = &csid->clock[i];
> @@ -477,13 +481,7 @@ static int csid_set_clock_rates(struct csid_device *csid)
> !strcmp(clock->name, "csi1") ||
> !strcmp(clock->name, "csi2") ||
> !strcmp(clock->name, "csi3")) {
> - const struct csid_format *f = csid_get_fmt_entry(
> - csid->formats,
> - csid->nformats,
> - csid->fmt[MSM_CSIPHY_PAD_SINK].code);
> - u8 num_lanes = csid->phy.lane_cnt;
> - u64 min_rate = pixel_clock * f->bpp /
> - (2 * num_lanes * 4);
> + u64 min_rate = link_freq / 4;
> long rate;
>
> camss_add_clock_margin(&min_rate);
> diff --git a/drivers/media/platform/qcom/camss/camss-csiphy-2ph-1-0.c b/drivers/media/platform/qcom/camss/camss-csiphy-2ph-1-0.c
> index 12bce391d71f..30b454c369ab 100644
> --- a/drivers/media/platform/qcom/camss/camss-csiphy-2ph-1-0.c
> +++ b/drivers/media/platform/qcom/camss/camss-csiphy-2ph-1-0.c
> @@ -51,16 +51,13 @@ static void csiphy_reset(struct csiphy_device *csiphy)
> *
> * Helper function to calculate settle count value. This is
> * based on the CSI2 T_hs_settle parameter which in turn
> - * is calculated based on the CSI2 transmitter pixel clock
> - * frequency.
> + * is calculated based on the CSI2 transmitter link frequency.
> *
> - * Return settle count value or 0 if the CSI2 pixel clock
> - * frequency is not available
> + * Return settle count value or 0 if the CSI2 link frequency
> + * is not available
> */
> -static u8 csiphy_settle_cnt_calc(u32 pixel_clock, u8 bpp, u8 num_lanes,
> - u32 timer_clk_rate)
> +static u8 csiphy_settle_cnt_calc(s64 link_freq, u32 timer_clk_rate)
> {
> - u32 mipi_clock; /* Hz */
> u32 ui; /* ps */
> u32 timer_period; /* ps */
> u32 t_hs_prepare_max; /* ps */
> @@ -68,8 +65,10 @@ static u8 csiphy_settle_cnt_calc(u32 pixel_clock, u8 bpp, u8 num_lanes,
> u32 t_hs_settle; /* ps */
> u8 settle_cnt;
>
> - mipi_clock = pixel_clock * bpp / (2 * num_lanes);
> - ui = div_u64(1000000000000LL, mipi_clock);
> + if (link_freq <= 0)
> + return 0;
> +
> + ui = div_u64(1000000000000LL, link_freq);
> ui /= 2;
> t_hs_prepare_max = 85000 + 6 * ui;
> t_hs_prepare_zero_min = 145000 + 10 * ui;
> @@ -83,15 +82,14 @@ static u8 csiphy_settle_cnt_calc(u32 pixel_clock, u8 bpp, u8 num_lanes,
>
> static void csiphy_lanes_enable(struct csiphy_device *csiphy,
> struct csiphy_config *cfg,
> - u32 pixel_clock, u8 bpp, u8 lane_mask)
> + s64 link_freq, u8 lane_mask)
> {
> struct csiphy_lanes_cfg *c = &cfg->csi2->lane_cfg;
> u8 settle_cnt;
> u8 val, l = 0;
> int i = 0;
>
> - settle_cnt = csiphy_settle_cnt_calc(pixel_clock, bpp, c->num_data,
> - csiphy->timer_clk_rate);
> + settle_cnt = csiphy_settle_cnt_calc(link_freq, csiphy->timer_clk_rate);
>
> writel_relaxed(0x1, csiphy->base +
> CAMSS_CSI_PHY_GLBL_T_INIT_CFG0);
> diff --git a/drivers/media/platform/qcom/camss/camss-csiphy-3ph-1-0.c b/drivers/media/platform/qcom/camss/camss-csiphy-3ph-1-0.c
> index 97cb9de85031..da7c3d3f9a10 100644
> --- a/drivers/media/platform/qcom/camss/camss-csiphy-3ph-1-0.c
> +++ b/drivers/media/platform/qcom/camss/camss-csiphy-3ph-1-0.c
> @@ -107,24 +107,23 @@ static irqreturn_t csiphy_isr(int irq, void *dev)
> *
> * Helper function to calculate settle count value. This is
> * based on the CSI2 T_hs_settle parameter which in turn
> - * is calculated based on the CSI2 transmitter pixel clock
> - * frequency.
> + * is calculated based on the CSI2 transmitter link frequency.
> *
> - * Return settle count value or 0 if the CSI2 pixel clock
> - * frequency is not available
> + * Return settle count value or 0 if the CSI2 link frequency
> + * is not available
> */
> -static u8 csiphy_settle_cnt_calc(u32 pixel_clock, u8 bpp, u8 num_lanes,
> - u32 timer_clk_rate)
> +static u8 csiphy_settle_cnt_calc(s64 link_freq, u32 timer_clk_rate)
> {
> - u32 mipi_clock; /* Hz */
> u32 ui; /* ps */
> u32 timer_period; /* ps */
> u32 t_hs_prepare_max; /* ps */
> u32 t_hs_settle; /* ps */
> u8 settle_cnt;
>
> - mipi_clock = pixel_clock * bpp / (2 * num_lanes);
> - ui = div_u64(1000000000000LL, mipi_clock);
> + if (link_freq <= 0)
> + return 0;
> +
> + ui = div_u64(1000000000000LL, link_freq);
> ui /= 2;
> t_hs_prepare_max = 85000 + 6 * ui;
> t_hs_settle = t_hs_prepare_max;
> @@ -137,15 +136,14 @@ static u8 csiphy_settle_cnt_calc(u32 pixel_clock, u8 bpp, u8 num_lanes,
>
> static void csiphy_lanes_enable(struct csiphy_device *csiphy,
> struct csiphy_config *cfg,
> - u32 pixel_clock, u8 bpp, u8 lane_mask)
> + s64 link_freq, u8 lane_mask)
> {
> struct csiphy_lanes_cfg *c = &cfg->csi2->lane_cfg;
> u8 settle_cnt;
> u8 val, l = 0;
> int i;
>
> - settle_cnt = csiphy_settle_cnt_calc(pixel_clock, bpp, c->num_data,
> - csiphy->timer_clk_rate);
> + settle_cnt = csiphy_settle_cnt_calc(link_freq, csiphy->timer_clk_rate);
>
> val = BIT(c->clk.pos);
> for (i = 0; i < c->num_data; i++)
> diff --git a/drivers/media/platform/qcom/camss/camss-csiphy.c b/drivers/media/platform/qcom/camss/camss-csiphy.c
> index 509c9a59c09c..40384d7ca78c 100644
> --- a/drivers/media/platform/qcom/camss/camss-csiphy.c
> +++ b/drivers/media/platform/qcom/camss/camss-csiphy.c
> @@ -102,23 +102,23 @@ static u8 csiphy_get_bpp(const struct csiphy_format *formats,
> static int csiphy_set_clock_rates(struct csiphy_device *csiphy)
> {
> struct device *dev = csiphy->camss->dev;
> - u32 pixel_clock;
> + s64 link_freq;
> int i, j;
> int ret;
>
> - ret = camss_get_pixel_clock(&csiphy->subdev.entity, &pixel_clock);
> - if (ret)
> - pixel_clock = 0;
> + u8 bpp = csiphy_get_bpp(csiphy->formats, csiphy->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);
> + 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]) {
> - u8 bpp = csiphy_get_bpp(csiphy->formats,
> - csiphy->nformats,
> - csiphy->fmt[MSM_CSIPHY_PAD_SINK].code);
> - u8 num_lanes = csiphy->cfg.csi2->lane_cfg.num_data;
> - u64 min_rate = pixel_clock * bpp / (2 * num_lanes * 4);
> + u64 min_rate = link_freq / 4;
> long round_rate;
>
> camss_add_clock_margin(&min_rate);
> @@ -238,22 +238,18 @@ static u8 csiphy_get_lane_mask(struct csiphy_lanes_cfg *lane_cfg)
> static int csiphy_stream_on(struct csiphy_device *csiphy)
> {
> struct csiphy_config *cfg = &csiphy->cfg;
> - u32 pixel_clock;
> + s64 link_freq;
> u8 lane_mask = csiphy_get_lane_mask(&cfg->csi2->lane_cfg);
> u8 bpp = csiphy_get_bpp(csiphy->formats, csiphy->nformats,
> csiphy->fmt[MSM_CSIPHY_PAD_SINK].code);
> + u8 num_lanes = csiphy->cfg.csi2->lane_cfg.num_data;
> u8 val;
> - int ret;
>
> - ret = camss_get_pixel_clock(&csiphy->subdev.entity, &pixel_clock);
> - if (ret) {
> - dev_err(csiphy->camss->dev,
> - "Cannot get CSI2 transmitter's pixel clock\n");
> - return -EINVAL;
> - }
> - if (!pixel_clock) {
> + link_freq = camss_get_link_freq(&csiphy->subdev.entity, bpp, num_lanes);
> +
> + if (link_freq < 0) {
> dev_err(csiphy->camss->dev,
> - "Got pixel clock == 0, cannot continue\n");
> + "Cannot get CSI2 transmitter's link frequency\n");
> return -EINVAL;
> }
>
> @@ -268,7 +264,7 @@ static int csiphy_stream_on(struct csiphy_device *csiphy)
> writel_relaxed(val, csiphy->base_clk_mux);
> wmb();
>
> - csiphy->ops->lanes_enable(csiphy, cfg, pixel_clock, bpp, lane_mask);
> + csiphy->ops->lanes_enable(csiphy, cfg, link_freq, lane_mask);
>
> return 0;
> }
> diff --git a/drivers/media/platform/qcom/camss/camss-csiphy.h b/drivers/media/platform/qcom/camss/camss-csiphy.h
> index f7967ef836dc..d71b8bc6ec00 100644
> --- a/drivers/media/platform/qcom/camss/camss-csiphy.h
> +++ b/drivers/media/platform/qcom/camss/camss-csiphy.h
> @@ -50,7 +50,7 @@ struct csiphy_hw_ops {
> void (*reset)(struct csiphy_device *csiphy);
> void (*lanes_enable)(struct csiphy_device *csiphy,
> struct csiphy_config *cfg,
> - u32 pixel_clock, u8 bpp, u8 lane_mask);
> + s64 link_freq, u8 lane_mask);
> void (*lanes_disable)(struct csiphy_device *csiphy,
> struct csiphy_config *cfg);
> irqreturn_t (*isr)(int irq, void *dev);
> diff --git a/drivers/media/platform/qcom/camss/camss.c b/drivers/media/platform/qcom/camss/camss.c
> index 7c0f669f8aa6..eb8fb8c34acd 100644
> --- a/drivers/media/platform/qcom/camss/camss.c
> +++ b/drivers/media/platform/qcom/camss/camss.c
> @@ -548,6 +548,29 @@ struct media_entity *camss_find_sensor(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
> + *
> + * 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 media_entity *sensor;
> + struct v4l2_subdev *subdev;
> +
> + sensor = camss_find_sensor(entity);
> + if (!sensor)
> + return -ENODEV;
> +
> + subdev = media_entity_to_v4l2_subdev(sensor);
> +
> + return v4l2_get_link_freq(subdev->ctrl_handler, bpp, 2 * lanes);
> +}
> +
> /*
> * camss_get_pixel_clock - Get pixel clock rate from sensor
> * @entity: Media entity in the current pipeline
> diff --git a/drivers/media/platform/qcom/camss/camss.h b/drivers/media/platform/qcom/camss/camss.h
> index 3a0484683cd6..86cdc25189eb 100644
> --- a/drivers/media/platform/qcom/camss/camss.h
> +++ b/drivers/media/platform/qcom/camss/camss.h
> @@ -108,6 +108,8 @@ 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_entity *camss_find_sensor(struct media_entity *entity);
> +s64 camss_get_link_freq(struct media_entity *entity, unsigned int bpp,
> + unsigned int lanes);
> int camss_get_pixel_clock(struct media_entity *entity, u32 *pixel_clock);
> int camss_pm_domain_on(struct camss *camss, int id);
> void camss_pm_domain_off(struct camss *camss, int id);
> --
> 2.17.1
>

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In reply to: Andrey Konovalov: "[PATCH v2 2/3] media: camss: use v4l2_get_link_freq() to calculate the relevant clocks"
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