Re: [PATCH V2 2/2] media: i2c: imx219: Support four-lane operation

[Dave Stevenson <dave.stevenson@raspberrypi.com>]

Hi Adam

On Thu, 16 Jun 2022 at 13:31, 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.
>
> Since the link frequency and number of lanes is extracted from the
> endpoint, move the endpoint handling into the probe function and
> out of the imx219_check_hwcfg.  This simplifies the imx219_check_hwcfg
> just a bit.
>
> Signed-off-by: Adam Ford <aford173@gmail.com>
> ---
> 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 a43eed143999..0d9004a5c4d2 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
> @@ -306,6 +312,10 @@ 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",
> @@ -481,6 +491,9 @@ struct imx219 {
>
>         /* Streaming on/off */
>         bool streaming;
> +
> +       /* Two or Four lanes */
> +       u8 lanes;
>  };
>
>  static inline struct imx219 *to_imx219(struct v4l2_subdev *_sd)
> @@ -943,6 +956,13 @@ 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);
> @@ -960,6 +980,13 @@ 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);
> @@ -1191,6 +1218,11 @@ 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)
>  {
> @@ -1212,15 +1244,16 @@ 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;
>
> @@ -1315,67 +1348,76 @@ 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 imx219 *imx219, u64 link_frequency)
>  {
> -       struct fwnode_handle *endpoint;
> +       struct i2c_client *client = v4l2_get_subdevdata(&imx219->sd);
> +
> +       /* Check the number of MIPI CSI2 data lanes */
> +       if (imx219->lanes != 2 && imx219->lanes != 4) {
> +               dev_err(&client->dev, "only 2 or 4 data lanes are currently supported\n");
> +               return -EINVAL;
> +       }
> +
> +       if (link_frequency != ((imx219->lanes == 2) ?
> +                             IMX219_DEFAULT_LINK_FREQ : IMX219_DEFAULT_LINK_FREQ_4LANE)) {
> +               dev_err(&client->dev, "Link frequency not supported: %lld\n",
> +                       link_frequency);
> +               return -EINVAL;
> +       }
> +
> +       return 0;
> +}
> +
> +static int imx219_probe(struct i2c_client *client)
> +{
> +       struct device *dev = &client->dev;
> +       struct imx219 *imx219;
>         struct v4l2_fwnode_endpoint ep_cfg = {
>                 .bus_type = V4L2_MBUS_CSI2_DPHY
>         };
> -       int ret = -EINVAL;
> +       struct fwnode_handle *endpoint;
> +       int ret = 0;
> +       u64 link_frequency = 0;
>
> +       imx219 = devm_kzalloc(&client->dev, sizeof(*imx219), GFP_KERNEL);
> +       if (!imx219)
> +               return -ENOMEM;
> +
> +       v4l2_i2c_subdev_init(&imx219->sd, client, &imx219_subdev_ops);
> +
> +       /* Fetch the endpoint to extract lanes and link-frequency */
>         endpoint = fwnode_graph_get_next_endpoint(dev_fwnode(dev), NULL);
>         if (!endpoint) {
>                 dev_err(dev, "endpoint node not found\n");
> -               return -EINVAL;
> +               ret = -EINVAL;
> +               goto fwnode_cleanup;
>         }
>
>         if (v4l2_fwnode_endpoint_alloc_parse(endpoint, &ep_cfg)) {
>                 dev_err(dev, "could not parse endpoint\n");
> -               goto error_out;
> +               ret = -EINVAL;
> +               goto fwnode_cleanup;
>         }
>
> -       /* 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");
> -               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) {
> +       if (ep_cfg.nr_of_link_frequencies != 1) {
>                 dev_err(dev, "link-frequency property not found in DT\n");
> -               goto error_out;
> -       }
> -
> -       if (ep_cfg.nr_of_link_frequencies != 1 ||
> -           ep_cfg.link_frequencies[0] != IMX219_DEFAULT_LINK_FREQ) {
> -               dev_err(dev, "Link frequency not supported: %lld\n",
> -                       ep_cfg.link_frequencies[0]);
> -               goto error_out;
> +               ret = -EINVAL;
> +               goto fwnode_cleanup;
>         }
> +       link_frequency = ep_cfg.link_frequencies[0];
>
> -       ret = 0;
> -
> -error_out:
> +       /* Cleanup endpoint and handle any errors from above */
> +fwnode_cleanup:
>         v4l2_fwnode_endpoint_free(&ep_cfg);
>         fwnode_handle_put(endpoint);

Having a "goto" to the middle of a function, and then if(ret) return
ret; is horrid. Working with diffs has messed this up a bit which is
why I hadn't noticed it in the last patch set, but I was about to
comment that link_frequency doesn't need to be initialised to 0 above,
but it does due to this (except it should take the return path).

I'm not quite sure why you need to move the fwnode calls out of
imx219_check_hwcfg. Pass in struct imx219 *imx219 and it can check the
link_frequency and assign imx219->lanes with the values it was already
validating. You can drop the struct device *dev as it is available via
imx219->sd->dev, initialised by v4l2_i2c_subdev_init. The
v4l2_fwnode_endpoint_free and fwnode_handle_put can then remain at the
end of the function as common cleanup code.
Rename imx219_check_hwcfg to imx219_read_hwcfg if the name offends as
it is now doing more than just checking it.

  Dave

> -
> -       return ret;
> -}
> -
> -static int imx219_probe(struct i2c_client *client)
> -{
> -       struct device *dev = &client->dev;
> -       struct imx219 *imx219;
> -       int ret;
> -
> -       imx219 = devm_kzalloc(&client->dev, sizeof(*imx219), GFP_KERNEL);
> -       if (!imx219)
> -               return -ENOMEM;
> -
> -       v4l2_i2c_subdev_init(&imx219->sd, client, &imx219_subdev_ops);
> +       if (ret)
> +               return ret;
>
>         /* Check the hardware configuration in device tree */
> -       if (imx219_check_hwcfg(dev))
> +       if (imx219_check_hwcfg(imx219, link_frequency))
>                 return -EINVAL;
>
>         /* Get system clock (xclk) */
> --
> 2.34.1
>