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Date: Tue, 21 Jun 2022 17:05:00 +0100
From: Dave Stevenson <dave.stevenson@...pberrypi.com>
To: Adam Ford <aford173@...il.com>
Cc: Linux Media Mailing List <linux-media@...r.kernel.org>,
Mauro Carvalho Chehab <mchehab@...nel.org>,
LKML <linux-kernel@...r.kernel.org>,
Adam Ford-BE <aford@...conembedded.com>
Subject: Re: [PATCH V2 2/2] media: i2c: imx219: Support four-lane operation
Hi Adam
On Thu, 16 Jun 2022 at 13:31, Adam Ford <aford173@...il.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@...il.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
>
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