Re: [PATCH v8 07/11] media: i2c: ov772x: Support frame interval handling

From: jacopo mondi
Date: Wed Jan 31 2018 - 07:49:02 EST

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In reply to: Laurent Pinchart: "Re: [PATCH v8 07/11] media: i2c: ov772x: Support frame interval handling"
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Hi Laurent,
thanks for review

Resuming here the brief conversation on #v4l with you and Hans...

On Wed, Jan 31, 2018 at 12:34:59PM +0200, Laurent Pinchart wrote:
> Hi Jacopo,
>
> Thank you for the patch.
>
> On Tuesday, 30 January 2018 11:58:18 EET Jacopo Mondi wrote:
> > Add support to ov772x driver for frame intervals handling and enumeration.
> > Tested with 10MHz and 24MHz input clock at VGA and QVGA resolutions for
> > 10, 15 and 30 frame per second rates.
> >
> > Signed-off-by: Jacopo Mondi <jacopo+renesas@xxxxxxxxxx>
> > ---
> > drivers/media/i2c/ov772x.c | 210 ++++++++++++++++++++++++++++++++++++++----
> > 1 file changed, 193 insertions(+), 17 deletions(-)
> >
> > diff --git a/drivers/media/i2c/ov772x.c b/drivers/media/i2c/ov772x.c
> > index 23106d7..28de254 100644
> > --- a/drivers/media/i2c/ov772x.c
> > +++ b/drivers/media/i2c/ov772x.c
>
> [snip]
>
> > @@ -373,6 +378,19 @@
> > #define VERSION(pid, ver) ((pid<<8)|(ver&0xFF))
> >
> > /*
> > + * Frame size (including blanking lines)
> > + */
> > +#define VGA_FRAME_SIZE (510 * 748)
> > +#define QVGA_FRAME_SIZE (278 * 576)
>
> Those two macros are not used, you can drop them.
>
> > +/*
> > + * Input clock frequencies
> > + */
> > +static const u8 ov772x_com4_vals[] = { PLL_BYPASS, PLL_4x, PLL_6x, PLL_8x
> > };
> > +static const unsigned int ov772x_pll_mult[] = { 1, 4, 6, 8 };
> > +#define OV772X_PLL_N_MULT ARRAY_SIZE(ov772x_pll_mult)
>
> I think it would be clearer if you used ARRAY_SIZE(ov772x_pll_mult) directly
> in the code.
>
> Maybe nitpicking a bit, but I wouldgroup the com4 values and multipliers in a
> structure:
>
> static const struct {
> unsigned int mult;
> u8 com4;
> } ov772x_pll_mult[] = {
> { 1, PLL_BYPASS },
> { 4, PLL_4x },
> { 6, PLL_6x },
> { 8, PLL_8x },
> };
>
> That ensures that the two arrays stay in sync as there's only one array left.
>
> > +/*
> > * struct
> > */
> >
> > @@ -388,6 +406,7 @@ struct ov772x_color_format {
> > struct ov772x_win_size {
> > char *name;
> > unsigned char com7_bit;
> > + unsigned int sizeimage;
> > struct v4l2_rect rect;
> > };
> >
> > @@ -404,6 +423,7 @@ struct ov772x_priv {
> > unsigned short flag_hflip:1;
> > /* band_filter = COM8[5] ? 256 - BDBASE : 0 */
> > unsigned short band_filter;
> > + unsigned int fps;
> > };
> >
> > /*
> > @@ -487,27 +507,35 @@ static const struct ov772x_color_format ov772x_cfmts[]
> > = {
> >
> > static const struct ov772x_win_size ov772x_win_sizes[] = {
> > {
> > - .name = "VGA",
> > - .com7_bit = SLCT_VGA,
> > + .name = "VGA",
> > + .com7_bit = SLCT_VGA,
> > + .sizeimage = 381480,
>
> I'd write this 510 * 748.
>
> > .rect = {
> > - .left = 140,
> > - .top = 14,
> > - .width = VGA_WIDTH,
> > - .height = VGA_HEIGHT,
> > + .left = 140,
> > + .top = 14,
> > + .width = VGA_WIDTH,
> > + .height = VGA_HEIGHT,
> > },
> > }, {
> > - .name = "QVGA",
> > - .com7_bit = SLCT_QVGA,
> > + .name = "QVGA",
> > + .com7_bit = SLCT_QVGA,
> > + .sizeimage = 160128,
>
> And this 278 * 576. It makes the value less magic.
>
> > .rect = {
> > - .left = 252,
> > - .top = 6,
> > - .width = QVGA_WIDTH,
> > - .height = QVGA_HEIGHT,
> > + .left = 252,
> > + .top = 6,
> > + .width = QVGA_WIDTH,
> > + .height = QVGA_HEIGHT,
> > },
> > },
> > };
> >
> > /*
> > + * frame rate settings lists
> > + */
> > +unsigned int ov772x_frame_intervals[] = { 5, 10, 15, 20, 30, 60 };
> > +#define OV772X_N_FRAME_INTERVALS ARRAY_SIZE(ov772x_frame_intervals)
> > +
> > +/*
> > * general function
> > */
> >
> > @@ -574,6 +602,124 @@ static int ov772x_s_stream(struct v4l2_subdev *sd, int
> > enable) return 0;
> > }
> >
> > +static int ov772x_set_frame_rate(struct ov772x_priv *priv,
> > + struct v4l2_fract *tpf,
> > + const struct ov772x_color_format *cfmt,
> > + const struct ov772x_win_size *win)
> > +{
> > + struct i2c_client *client = v4l2_get_subdevdata(&priv->subdev);
> > + unsigned int fps = tpf->denominator / tpf->numerator;
>
> tpf->numerator could be 0.
>
> > + unsigned int fin = clk_get_rate(priv->clk);
>
> Clock rates are unsigned long.
>
> > + unsigned int rate_prev;
> > + unsigned int fsize;
> > + unsigned int pclk;
> > + unsigned int rate;
> > + unsigned int idx;
> > + unsigned int i;
> > + u8 clkrc = 0;
> > + u8 com4 = 0;
> > + int ret;
> > +
> > + /* Approximate to the closest supported frame interval. */
> > + rate_prev = ~0L;
> > + for (i = 0, idx = 0; i < OV772X_N_FRAME_INTERVALS; i++) {
> > + rate = abs(fps - ov772x_frame_intervals[i]);
> > + if (rate < rate_prev) {
> > + idx = i;
> > + rate_prev = rate;
>
> I'd call the rate_prev and rate variables best_diff and diff respectively.
>
> > + }
> > + }
> > + fps = ov772x_frame_intervals[idx];
> > +
> > + /* Use image size (with blankings) to calculate desired pixel clock. */
> > + if ((cfmt->com7 & OFMT_RGB) == OFMT_RGB ||
> > + (cfmt->com7 & OFMT_YUV) == OFMT_YUV)
> > + fsize = win->sizeimage * 2;
> > + else if ((cfmt->com7 & OFMT_BRAW) == OFMT_BRAW)
>
> I think all these should test (cfmt->com7 & OFMT_MASK) == ...
>
> > + fsize = win->sizeimage;
> > +
> > + pclk = fps * fsize;
> > +
> > + /*
> > + * Pixel clock generation circuit is pretty simple:
> > + *
> > + * Fin -> [ / CLKRC_div] -> [ * PLL_mult] -> pclk
> > + *
> > + * Try to approximate the desired pixel clock testing all available
> > + * PLL multipliers (1x, 4x, 6x, 8x) and calculate corresponding
> > + * divisor with:
> > + *
> > + * div = PLL_mult * Fin / pclk
> > + *
> > + * and re-calculate the pixel clock using it:
> > + *
> > + * pclk = Fin * PLL_mult / CLKRC_div
> > + *
> > + * Choose the PLL_mult and CLKRC_div pair that gives a pixel clock
> > + * closer to the desired one.
> > + *
> > + * The desired pixel clock is calculated using a known frame size
> > + * (blanking included) and FPS.
> > + */
> > + rate_prev = ~0L;
> > + for (i = 0; i < OV772X_PLL_N_MULT; i++) {
> > + unsigned int pll_mult = ov772x_pll_mult[i];
> > + unsigned int pll_out = pll_mult * fin;
> > + unsigned int t_pclk;
> > + unsigned int div;
> > +
> > + if (pll_out < pclk)
> > + continue;
> > +
> > + div = DIV_ROUND_CLOSEST(pll_out, pclk);
> > + t_pclk = DIV_ROUND_CLOSEST((fin * pll_mult), div);
>
> No need for the inner parentheses.
>
> > + rate = abs(pclk - t_pclk);
> > + if (rate < rate_prev) {
> > + rate_prev = rate;
> > + clkrc = CLKRC_DIV(div);
> > + com4 = ov772x_com4_vals[i];
> > + }
> > + }
> > +
> > + ret = ov772x_write(client, COM4, com4 | COM4_RESERVED);
> > + if (ret < 0)
> > + return ret;
> > +
> > + ret = ov772x_write(client, CLKRC, clkrc | CLKRC_RESERVED);
> > + if (ret < 0)
> > + return ret;
> > +
> > + tpf->numerator = 1;
> > + tpf->denominator = fps;
> > + priv->fps = tpf->denominator;
> > +
> > + return 0;
> > +}
> > +
> > +static int ov772x_g_frame_interval(struct v4l2_subdev *sd,
> > + struct v4l2_subdev_frame_interval *ival)
> > +{
> > + struct ov772x_priv *priv = to_ov772x(sd);
> > + struct v4l2_fract *tpf = &ival->interval;
> > +
> > + memset(ival->reserved, 0, sizeof(ival->reserved));
> > + tpf->numerator = 1;
> > + tpf->denominator = priv->fps;
> > +
> > + return 0;
> > +}
> > +
> > +static int ov772x_s_frame_interval(struct v4l2_subdev *sd,
> > + struct v4l2_subdev_frame_interval *ival)
> > +{
> > + struct ov772x_priv *priv = to_ov772x(sd);
> > + struct v4l2_fract *tpf = &ival->interval;
> > +
> > + memset(ival->reserved, 0, sizeof(ival->reserved));
> > +
> > + return ov772x_set_frame_rate(priv, tpf, priv->cfmt, priv->win);
> > +}
> > +
> > static int ov772x_s_ctrl(struct v4l2_ctrl *ctrl)
> > {
> > struct ov772x_priv *priv = container_of(ctrl->handler,
> > @@ -757,6 +903,7 @@ static int ov772x_set_params(struct ov772x_priv *priv,
> > const struct ov772x_win_size *win)
> > {
> > struct i2c_client *client = v4l2_get_subdevdata(&priv->subdev);
> > + struct v4l2_fract tpf;
> > int ret;
> > u8 val;
> >
> > @@ -885,6 +1032,13 @@ static int ov772x_set_params(struct ov772x_priv *priv,
> > if (ret < 0)
> > goto ov772x_set_fmt_error;
> >
> > + /* COM4, CLKRC: Set pixel clock and framerate. */
> > + tpf.numerator = 1;
> > + tpf.denominator = priv->fps;
> > + ret = ov772x_set_frame_rate(priv, &tpf, cfmt, win);
> > + if (ret < 0)
> > + goto ov772x_set_fmt_error;
> > +
> > /*
> > * set COM8
> > */
> > @@ -1043,6 +1197,24 @@ static const struct v4l2_subdev_core_ops
> > ov772x_subdev_core_ops = { .s_power = ov772x_s_power,
> > };
> >
> > +static int ov772x_enum_frame_interval(struct v4l2_subdev *sd,
> > + struct v4l2_subdev_pad_config *cfg,
> > + struct v4l2_subdev_frame_interval_enum *fie)
> > +{
> > + if (fie->pad || fie->index >= OV772X_N_FRAME_INTERVALS)
> > + return -EINVAL;
> > +
> > + if (fie->width != VGA_WIDTH && fie->width != QVGA_WIDTH)
> > + return -EINVAL;
> > + if (fie->height != VGA_HEIGHT && fie->height != QVGA_HEIGHT)
> > + return -EINVAL;
> > +
> > + fie->interval.numerator = 1;
> > + fie->interval.denominator = ov772x_frame_intervals[fie->index];
> > +
> > + return 0;
> > +}
>
> The more I think about it, the more I believe that the subdev frame interval
> enumeration operation is nonsense. This particular sensor is not restricted to
> a fixed list of frame intervals. Sensors should really expose the pixel clock
> and blanking as controls, and higher level parameters such as frame intervals
> should then be handled by the bridge driver.

I thought the same while implementing this, exposing a limited set of
discrete values is limiting when the hw and the driver actually
support a continuous range of possible values.

But I agree with Hans (of course, it makes things easier for me :) that if
that's what the API offers right now, we should not hold back this
series waiting for a better one to be available.

I'm happy to keep discussing this if I can help in some way, but I
think it's outside the scope of this patch.

>
> I won't nack this patch due to this as I want to see this series merged, so
> with the above small issues fixed you have my

Thanks.

I then would like to discuss the CEU driver behavior when no
enum_frame_interval subdev operation is available, I will reply to my
own patch on this.

Thanks
j

>
> Reviewed-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
>
> but we're going in the wrong direction.
>
> --
> Regards,
>
> Laurent Pinchart
>

Next message: Andy Shevchenko: "Re: [PATCH] drivers: regulator: fan53555: fixed a coding style issue"
Previous message: Simon Horman: "Re: [PATCH V2] print kdump kernel loaded status in stack dump"
In reply to: Laurent Pinchart: "Re: [PATCH v8 07/11] media: i2c: ov772x: Support frame interval handling"
Next in thread: Jacopo Mondi: "[PATCH v8 09/11] media: i2c: tw9910: Remove soc_camera dependencies"
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