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

[Andrey Konovalov <andrey.konovalov@xxxxxxxxxx>]

Hi Jacopo,

On 18.02.2021 11:07, Jacopo Mondi wrote:
> 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 ?

Unfortunately no.
There are no any details in the public datasheet on that - just
the formula itself (less than 1 line of text).

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

Thanks!

-- Andrey

> 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