Re: [PATCH v1 078/107] media: ti-vpe: cal: Don't store external rate in cal_camerarx

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Kieran,

On Wed, Jun 17, 2020 at 11:16:45AM +0100, Kieran Bingham wrote:
> On 17/06/2020 11:05, Laurent Pinchart wrote:
> > On Wed, Jun 17, 2020 at 10:56:29AM +0100, Kieran Bingham wrote:
> >> On 15/06/2020 00:59, Laurent Pinchart wrote:
> >>> The external pixel rate is retrieved when starting the camerarx and only
> >>> used then. There's no need to store it in the cal_camerarx structure, it
> >>> can be returned by cal_camerarx_get_external_info() and explicitly
> >>> passed to cal_camerarx_config().
> >>>
> >>> While at it, rename cal_camerarx_get_external_info() to
> >>> cal_camerarx_get_external_rate() to better reflect the function's
> >>> purpose.
> >>>
> >>> Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> >>> ---
> >>>  drivers/media/platform/ti-vpe/cal.c | 24 ++++++++++++------------
> >>>  1 file changed, 12 insertions(+), 12 deletions(-)
> >>>
> >>> diff --git a/drivers/media/platform/ti-vpe/cal.c b/drivers/media/platform/ti-vpe/cal.c
> >>> index 8326db0e4197..a11457909134 100644
> >>> --- a/drivers/media/platform/ti-vpe/cal.c
> >>> +++ b/drivers/media/platform/ti-vpe/cal.c
> >>> @@ -272,7 +272,6 @@ struct cal_camerarx {
> >>>  	struct v4l2_fwnode_endpoint	endpoint;
> >>>  	struct device_node	*sensor_node;
> >>>  	struct v4l2_subdev	*sensor;
> >>> -	unsigned int		external_rate;
> >>
> >> Here, external_rate is 32 bit,
> >>
> >>>  };
> >>>  
> >>>  struct cal_dev {
> >>> @@ -481,9 +480,10 @@ static void cal_quickdump_regs(struct cal_dev *cal)
> >>>   * ------------------------------------------------------------------
> >>>   */
> >>>  
> >>> -static int cal_camerarx_get_external_info(struct cal_camerarx *phy)
> >>> +static s64 cal_camerarx_get_external_rate(struct cal_camerarx *phy)
> >>>  {
> >>>  	struct v4l2_ctrl *ctrl;
> >>> +	s64 rate;
> >>
> >> and now it becomes a 64 bit value.
> >>
> >>>  
> >>>  	if (!phy->sensor)
> >>>  		return -ENODEV;
> >>> @@ -495,10 +495,10 @@ static int cal_camerarx_get_external_info(struct cal_camerarx *phy)
> >>>  		return -EPIPE;
> >>>  	}
> >>>  
> >>> -	phy->external_rate = v4l2_ctrl_g_ctrl_int64(ctrl);
> >>> -	phy_dbg(3, phy, "sensor Pixel Rate: %u\n", phy->external_rate);
> >>> +	rate = v4l2_ctrl_g_ctrl_int64(ctrl);
> >>> +	phy_dbg(3, phy, "sensor Pixel Rate: %llu\n", rate);
> >>>  
> >>> -	return 0;
> >>> +	return rate;
> >>>  }
> >>>  
> >>>  static void cal_camerarx_lane_config(struct cal_camerarx *phy)
> >>> @@ -554,7 +554,7 @@ static void cal_camerarx_disable(struct cal_camerarx *phy)
> >>>  #define TCLK_MISS	1
> >>>  #define TCLK_SETTLE	14
> >>>  
> >>> -static void cal_camerarx_config(struct cal_camerarx *phy,
> >>> +static void cal_camerarx_config(struct cal_camerarx *phy, s64 external_rate,
> >>>  				const struct cal_fmt *fmt)
> >>>  {
> >>>  	unsigned int reg0, reg1;
> >>> @@ -566,7 +566,7 @@ static void cal_camerarx_config(struct cal_camerarx *phy,
> >>>  
> >>>  	/* DPHY timing configuration */
> >>>  	/* CSI-2 is DDR and we only count used lanes. */
> >>> -	csi2_ddrclk_khz = phy->external_rate / 1000
> >>> +	csi2_ddrclk_khz = external_rate / 1000
> >>>  		/ (2 * num_lanes) * fmt->bpp;
> >>
> >> Which causes this calculation to fail on 32 bit ARM builds.
> >> (I'm building for the DRA76-EVM).
> > 
> > Oops :-/
> > 
> >> I've got the following fix up on the top of your tree to solve this, but
> >> I'm not particularly happy about having to break the calculation up (and
> >> re-use external_rate) though the use of do_div.
> >>
> >> From ca6ce335a852e34364bc45cb4240f703e4ea4248 Mon Sep 17 00:00:00 2001
> >> From: Kieran Bingham <kieran.bingham@ideasonboard.com>
> >> Date: Tue, 16 Jun 2020 16:19:04 +0100
> >> Subject: [PATCH] media: ti-vpe: cal: Use do_div() for 64 bit operations
> >>
> >> Support building the CAL driver on arm32 bit targets by updating the
> >> CSI2 clock calculation (which uses a signed 64 bit input value from
> >> the sensors pixel clock rate) to use the do_div() helpers.
> >>
> >> The calculation is split into distinct parts to maintain
> >> order of operations while making use of the do_div macro and further
> >> re-ordered to convert to kHz at the end to maintain precision.
> >>
> >> Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
> >> ---
> >>  drivers/media/platform/ti-vpe/cal-camerarx.c | 22 +++++++++++++++++---
> >>  1 file changed, 19 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/drivers/media/platform/ti-vpe/cal-camerarx.c
> >> b/drivers/media/platform/ti-vpe/cal-camerarx.c
> >> index 014ca46509db..0ef19a516902 100644
> >> --- a/drivers/media/platform/ti-vpe/cal-camerarx.c
> >> +++ b/drivers/media/platform/ti-vpe/cal-camerarx.c
> >> @@ -126,9 +126,25 @@ static void cal_camerarx_config(struct cal_camerarx
> >> *phy, s64 external_rate)
> >>         u32 num_lanes = mipi_csi2->num_data_lanes;
> >>
> >>         /* DPHY timing configuration */
> >> -       /* CSI-2 is DDR and we only count used lanes. */
> >> -       csi2_ddrclk_khz = external_rate / 1000
> >> -               / (2 * num_lanes) * phy->fmtinfo->bpp;
> >> +
> >> +       /*
> >> +        * CSI-2 is DDR and we only count used lanes.
> >> +        *
> >> +        * csi2_ddrclk_khz = external_rate / 1000
> >> +        *                   / (2 * num_lanes) * phy->fmtinfo->bpp;
> >> +        *
> >> +        * The equation is broken into separate statements to maintain
> >> +        * order of operations, and conversion to kHz is done last to
> >> +        * keep precision.
> >> +        *
> >> +        * The 64 bit external_rate is modified during this equation and
> >> +        * contains the result, not the original after calculation.
> >> +        */
> >> +       do_div(external_rate, 2 * num_lanes);
> >> +       external_rate *= phy->fmtinfo->bpp;
> >> +       do_div(external_rate, 1000);
> >> +       csi2_ddrclk_khz = external_rate;
> > 
> > How about
> > 
> > 	external_rate *= phy->fmtinfo->bpp;
> >  	do_div(external_rate, 2 * num_lanes * 1000);
> 
> Ah yes, that looks better indeed, and keeps the improved integer precision.
> 
> I believe the s64 external_rate should cope with the * bpp operation
> easily too, so I don't think there's any risk of an overflow there.
> 
> Squash it ;-)

Even better,

	csi2_ddrclk_khz = div_s64(external_rate * phy->fmtinfo->bpp,
				  2 * num_lanes * 1000);

> >> +
> >>         phy_dbg(1, phy, "csi2_ddrclk_khz: %d\n", csi2_ddrclk_khz);
> >>
> >>         /* THS_TERM: Programmed value = floor(20 ns/DDRClk period) */
> >> -- 
> >> 2.25.1
> >>
> >>
> >> If you have a better way to correctly calculate the rate (also noting
> >> that I moved the /1000 to the end, I'm not sure if that's more correct,
> >> or makes it stop following what the hardware would do) - please update
> >> accordingly, or feel free to squash this patch in as you wish.
> >>
> >>
> >> With the calculation corrected:
> >>
> >> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
> >>
> >> --
> >> Kieran
> >>
> >>
> >>>  	phy_dbg(1, phy, "csi2_ddrclk_khz: %d\n", csi2_ddrclk_khz);
> >>>  
> >>> @@ -667,13 +667,14 @@ static void cal_camerarx_wait_stop_state(struct cal_camerarx *phy)
> >>>  static int cal_camerarx_start(struct cal_camerarx *phy,
> >>>  			      const struct cal_fmt *fmt)
> >>>  {
> >>> +	s64 external_rate;
> >>>  	u32 sscounter;
> >>>  	u32 val;
> >>>  	int ret;
> >>>  
> >>> -	ret = cal_camerarx_get_external_info(phy);
> >>> -	if (ret < 0)
> >>> -		return ret;
> >>> +	external_rate = cal_camerarx_get_external_rate(phy);
> >>> +	if (external_rate < 0)
> >>> +		return external_rate;
> >>>  
> >>>  	ret = v4l2_subdev_call(phy->sensor, core, s_power, 1);
> >>>  	if (ret < 0 && ret != -ENOIOCTLCMD && ret != -ENODEV) {
> >>> @@ -719,7 +720,7 @@ static int cal_camerarx_start(struct cal_camerarx *phy,
> >>>  	reg_read(phy, CAL_CSI2_PHY_REG0);
> >>>  
> >>>  	/* Program the PHY timing parameters. */
> >>> -	cal_camerarx_config(phy, fmt);
> >>> +	cal_camerarx_config(phy, external_rate, fmt);
> >>>  
> >>>  	/*
> >>>  	 *    b. Assert the FORCERXMODE signal.
> >>> @@ -1034,7 +1035,6 @@ static struct cal_camerarx *cal_camerarx_create(struct cal_dev *cal,
> >>>  
> >>>  	phy->cal = cal;
> >>>  	phy->instance = instance;
> >>> -	phy->external_rate = 192000000;
> >>>  
> >>>  	phy->res = platform_get_resource_byname(pdev, IORESOURCE_MEM,
> >>>  						(instance == 0) ?

-- 
Regards,

Laurent Pinchart