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From:   Adam Ford <aford173@gmail.com>
Date:   Mon, 16 Jan 2023 10:36:22 -0600
Message-ID: <CAHCN7xLrVfN+CbGhUEB-iy54hu2tSHk7Ge0eEb-h41r44R3DEg@mail.gmail.com>
Subject: Re: [PATCH V4 2/2] media: i2c: imx219: Support four-lane operation
To:     Dave Stevenson <dave.stevenson@raspberrypi.com>
Cc:     linux-media@vger.kernel.org, aford@beaconembedded.com,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        linux-kernel@vger.kernel.org
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On Mon, Jan 16, 2023 at 8:42 AM Dave Stevenson
<dave.stevenson@raspberrypi.com> wrote:
>
> Hi Adam
>
> Sorry, for the delay.
>
> On Fri, 13 Jan 2023 at 18:41, Adam Ford <aford173@gmail.com> wrote:
> >
> > On Tue, Dec 20, 2022 at 6:08 AM Adam Ford <aford173@gmail.com> wrote:
> > >
> > > The imx219 camera is capable of either two-lane or four-lane
> > > operation.  When operating in four-lane, both the pixel rate and
> > > link frequency change. Regardless of the mode, however, both
> > > frequencies remain fixed.
> > >
> > > Helper functions are needed to read and set pixel and link frequencies
> > > which also reduces the number of fixed registers in the table of modes.
> > >
> > > Signed-off-by: Adam Ford <aford173@gmail.com>
>
> I can't test on 4 lanes, but 2 lane modes still work, and the code
> looks reasonable for 4 lanes.

Thanks!  For what it's worth, I tested this on an Renesas RZ/G2M SoC
which has both a 2-lane and 4-lane interface, and I didn't see any
difference in performance or image quality between the 2-lane and
4-lane modes.

adam
>
> Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
>
>
> > Gentle nudge on this.
> >
> > > ---
> > > V4:  Restore check for nr_of_link_frequencies and update commit message
> > > V3:  Keep the helper function doing the link and lane parsing to
> > >      keep th probe function small.
> > >
> > > V2:  Replace if-else statements with ternary operator
> > >      Fix 4-lane Link Rate.
> > >      Fix checking the link rate so only the link rate for
> > >      the given number of lanes is permitted.
> > >
> > > diff --git a/drivers/media/i2c/imx219.c b/drivers/media/i2c/imx219.c
> > > index 7f44d62047b6..b5fa4986470a 100644
> > > --- a/drivers/media/i2c/imx219.c
> > > +++ b/drivers/media/i2c/imx219.c
> > > @@ -42,10 +42,16 @@
> > >  /* External clock frequency is 24.0M */
> > >  #define IMX219_XCLK_FREQ               24000000
> > >
> > > -/* Pixel rate is fixed at 182.4M for all the modes */
> > > +/* Pixel rate is fixed for all the modes */
> > >  #define IMX219_PIXEL_RATE              182400000
> > > +#define IMX219_PIXEL_RATE_4LANE                280800000
> > >
> > >  #define IMX219_DEFAULT_LINK_FREQ       456000000
> > > +#define IMX219_DEFAULT_LINK_FREQ_4LANE 363000000
> > > +
> > > +#define IMX219_REG_CSI_LANE_MODE       0x0114
> > > +#define IMX219_CSI_2_LANE_MODE         0x01
> > > +#define IMX219_CSI_4_LANE_MODE         0x03
> > >
> > >  /* V_TIMING internal */
> > >  #define IMX219_REG_VTS                 0x0160
> > > @@ -299,6 +305,10 @@ static const s64 imx219_link_freq_menu[] = {
> > >         IMX219_DEFAULT_LINK_FREQ,
> > >  };
> > >
> > > +static const s64 imx219_link_freq_4lane_menu[] = {
> > > +       IMX219_DEFAULT_LINK_FREQ_4LANE,
> > > +};
> > > +
> > >  static const char * const imx219_test_pattern_menu[] = {
> > >         "Disabled",
> > >         "Color Bars",
> > > @@ -474,6 +484,9 @@ struct imx219 {
> > >
> > >         /* Streaming on/off */
> > >         bool streaming;
> > > +
> > > +       /* Two or Four lanes */
> > > +       u8 lanes;
> > >  };
> > >
> > >  static inline struct imx219 *to_imx219(struct v4l2_subdev *_sd)
> > > @@ -936,6 +949,13 @@ static int imx219_get_selection(struct v4l2_subdev *sd,
> > >         return -EINVAL;
> > >  }
> > >
> > > +static int imx219_configure_lanes(struct imx219 *imx219)
> > > +{
> > > +       return imx219_write_reg(imx219, IMX219_REG_CSI_LANE_MODE,
> > > +                               IMX219_REG_VALUE_08BIT, (imx219->lanes == 2) ?
> > > +                               IMX219_CSI_2_LANE_MODE : IMX219_CSI_4_LANE_MODE);
> > > +};
> > > +
> > >  static int imx219_start_streaming(struct imx219 *imx219)
> > >  {
> > >         struct i2c_client *client = v4l2_get_subdevdata(&imx219->sd);
> > > @@ -953,6 +973,13 @@ static int imx219_start_streaming(struct imx219 *imx219)
> > >                 goto err_rpm_put;
> > >         }
> > >
> > > +       /* Configure two or four Lane mode */
> > > +       ret = imx219_configure_lanes(imx219);
> > > +       if (ret) {
> > > +               dev_err(&client->dev, "%s failed to configure lanes\n", __func__);
> > > +               goto err_rpm_put;
> > > +       }
> > > +
> > >         /* Apply default values of current mode */
> > >         reg_list = &imx219->mode->reg_list;
> > >         ret = imx219_write_regs(imx219, reg_list->regs, reg_list->num_of_regs);
> > > @@ -1184,6 +1211,11 @@ static const struct v4l2_subdev_internal_ops imx219_internal_ops = {
> > >         .open = imx219_open,
> > >  };
> > >
> > > +static unsigned long imx219_get_pixel_rate(struct imx219 *imx219)
> > > +{
> > > +       return (imx219->lanes == 2) ? IMX219_PIXEL_RATE : IMX219_PIXEL_RATE_4LANE;
> > > +}
> > > +
> > >  /* Initialize control handlers */
> > >  static int imx219_init_controls(struct imx219 *imx219)
> > >  {
> > > @@ -1205,15 +1237,16 @@ static int imx219_init_controls(struct imx219 *imx219)
> > >         /* By default, PIXEL_RATE is read only */
> > >         imx219->pixel_rate = v4l2_ctrl_new_std(ctrl_hdlr, &imx219_ctrl_ops,
> > >                                                V4L2_CID_PIXEL_RATE,
> > > -                                              IMX219_PIXEL_RATE,
> > > -                                              IMX219_PIXEL_RATE, 1,
> > > -                                              IMX219_PIXEL_RATE);
> > > +                                              imx219_get_pixel_rate(imx219),
> > > +                                              imx219_get_pixel_rate(imx219), 1,
> > > +                                              imx219_get_pixel_rate(imx219));
> > >
> > >         imx219->link_freq =
> > >                 v4l2_ctrl_new_int_menu(ctrl_hdlr, &imx219_ctrl_ops,
> > >                                        V4L2_CID_LINK_FREQ,
> > >                                        ARRAY_SIZE(imx219_link_freq_menu) - 1, 0,
> > > -                                      imx219_link_freq_menu);
> > > +                                      (imx219->lanes == 2) ? imx219_link_freq_menu :
> > > +                                      imx219_link_freq_4lane_menu);
> > >         if (imx219->link_freq)
> > >                 imx219->link_freq->flags |= V4L2_CTRL_FLAG_READ_ONLY;
> > >
> > > @@ -1308,7 +1341,7 @@ static void imx219_free_controls(struct imx219 *imx219)
> > >         mutex_destroy(&imx219->mutex);
> > >  }
> > >
> > > -static int imx219_check_hwcfg(struct device *dev)
> > > +static int imx219_check_hwcfg(struct device *dev, struct imx219 *imx219)
> > >  {
> > >         struct fwnode_handle *endpoint;
> > >         struct v4l2_fwnode_endpoint ep_cfg = {
> > > @@ -1328,10 +1361,12 @@ static int imx219_check_hwcfg(struct device *dev)
> > >         }
> > >
> > >         /* Check the number of MIPI CSI2 data lanes */
> > > -       if (ep_cfg.bus.mipi_csi2.num_data_lanes != 2) {
> > > -               dev_err(dev, "only 2 data lanes are currently supported\n");
> > > +       if (ep_cfg.bus.mipi_csi2.num_data_lanes != 2 &&
> > > +           ep_cfg.bus.mipi_csi2.num_data_lanes != 4) {
> > > +               dev_err(dev, "only 2 or 4 data lanes are currently supported\n");
> > >                 goto error_out;
> > >         }
> > > +       imx219->lanes = ep_cfg.bus.mipi_csi2.num_data_lanes;
> > >
> > >         /* Check the link frequency set in device tree */
> > >         if (!ep_cfg.nr_of_link_frequencies) {
> > > @@ -1340,7 +1375,8 @@ static int imx219_check_hwcfg(struct device *dev)
> > >         }
> > >
> > >         if (ep_cfg.nr_of_link_frequencies != 1 ||
> > > -           ep_cfg.link_frequencies[0] != IMX219_DEFAULT_LINK_FREQ) {
> > > +          (ep_cfg.link_frequencies[0] != ((imx219->lanes == 2) ?
> > > +           IMX219_DEFAULT_LINK_FREQ : IMX219_DEFAULT_LINK_FREQ_4LANE))) {
> > >                 dev_err(dev, "Link frequency not supported: %lld\n",
> > >                         ep_cfg.link_frequencies[0]);
> > >                 goto error_out;
> > > @@ -1368,7 +1404,7 @@ static int imx219_probe(struct i2c_client *client)
> > >         v4l2_i2c_subdev_init(&imx219->sd, client, &imx219_subdev_ops);
> > >
> > >         /* Check the hardware configuration in device tree */
> > > -       if (imx219_check_hwcfg(dev))
> > > +       if (imx219_check_hwcfg(dev, imx219))
> > >                 return -EINVAL;
> > >
> > >         /* Get system clock (xclk) */
> > > --
> > > 2.34.1
> > >