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Message-ID: <CAPY8ntBG=ghLmFGkA4-Tg4pAzAv6jWARkyiZU-4uCVhQuwZa9Q@mail.gmail.com>
Date: Thu, 11 Sep 2025 12:11:36 +0100
From: Dave Stevenson <dave.stevenson@...pberrypi.com>
To: Maxime Ripard <mripard@...nel.org>
Cc: Mauro Carvalho Chehab <mchehab@...nel.org>, Mats Randgaard <matrandg@...co.com>,
Alain Volmat <alain.volmat@...s.st.com>, Sakari Ailus <sakari.ailus@...ux.intel.com>,
Hans Verkuil <hverkuil@...nel.org>, linux-media@...r.kernel.org,
linux-kernel@...r.kernel.org, Hans Verkuil <hans.verkuil@...co.com>
Subject: Re: [PATCH v2 3/4] media: tc358743: Fix the RGB MBUS format
Hi Maxime
On Thu, 11 Sept 2025 at 10:15, Maxime Ripard <mripard@...nel.org> wrote:
>
> The tc358743 is an HDMI to MIPI-CSI2 bridge. It supports two of the
> three HDMI 1.4 video formats: RGB 4:4:4 and YCbCr 422.
It accepts 3 HDMI video formats: 24bpp RGB 4:4:4, 24bpp YCbCr 4:4:4,
or 16bpp YCbCr 4:2:2.
It supports outputting the incoming video data as either 24bpp RGB
4:4:4 or 16bpp YCbCr 4:2:2, and will convert the incoming HDMI video
data to either of these.
(Rereading the datasheet it can also send YCbCr 4:4:4, but that's
non-standard as it by default reuses data type 0x24 which is RGB888,
but says it uses RAW12 packing!)
> RGB 4:4:4 is converted to the MIPI-CSI2 RGB888 video format, and listed
> in the driver as MEDIA_BUS_FMT_RGB888_1X24.
>
> Most CSI2 receiver drivers then map MEDIA_BUS_FMT_RGB888_1X24 to
> V4L2_PIX_FMT_RGB24.
>
> However, V4L2_PIX_FMT_RGB24 is defined as having its color components in
> the R, G and B order, from left to right. MIPI-CSI2 however defines the
> RGB888 format with blue first.
>
> This essentially means that the R and B will be swapped compared to what
> V4L2_PIX_FMT_RGB24 defines.
>
> The proper MBUS format would be BGR888, so let's use that.
>
> Fixes: d32d98642de6 ("[media] Driver for Toshiba TC358743 HDMI to CSI-2 bridge")
> Signed-off-by: Maxime Ripard <mripard@...nel.org>
> ---
> drivers/media/i2c/tc358743.c | 51 ++++++++++++++++++++++++++++++++++++--------
> 1 file changed, 42 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/media/i2c/tc358743.c b/drivers/media/i2c/tc358743.c
> index 1cc7636e446d77d7c6266ca86517496261d2b039..a3054cd823da4cf3db24c6b2bfbf0fcaa43f2814 100644
> --- a/drivers/media/i2c/tc358743.c
> +++ b/drivers/media/i2c/tc358743.c
> @@ -693,11 +693,21 @@ static void tc358743_set_csi_color_space(struct v4l2_subdev *sd)
> i2c_wr16_and_or(sd, CONFCTL, ~MASK_YCBCRFMT,
> MASK_YCBCRFMT_422_8_BIT);
> mutex_unlock(&state->confctl_mutex);
> break;
> case MEDIA_BUS_FMT_RGB888_1X24:
> - v4l2_dbg(2, debug, sd, "%s: RGB 888 24-bit\n", __func__);
> + /*
> + * The driver was initially introduced with RGB888
> + * support, but CSI really means BGR.
> + *
> + * Since we might have applications that would have
> + * hard-coded the RGB888, let's support both.
> + */
> + v4l2_warn(sd, "RGB format isn't actually supported by the hardware. The application should be fixed to use BGR.");
warn_once? Otherwise repeatedly setting the format to RGB888 will spam
the kernel log.
(Annoying that there doesn't appear to be a v4l2_warn_once macro)
> + fallthrough;
> + case MEDIA_BUS_FMT_BGR888_1X24:
> + v4l2_dbg(2, debug, sd, "%s: BGR 888 24-bit\n", __func__);
> i2c_wr8_and_or(sd, VOUT_SET2,
> ~(MASK_SEL422 | MASK_VOUT_422FIL_100) & 0xff,
> 0x00);
> i2c_wr8_and_or(sd, VI_REP, ~MASK_VOUT_COLOR_SEL & 0xff,
> MASK_VOUT_COLOR_RGB_FULL);
> @@ -1354,15 +1364,28 @@ static int tc358743_log_status(struct v4l2_subdev *sd)
> (i2c_rd16(sd, CSI_STATUS) & MASK_S_RXACT) ?
> "yes" : "no");
> v4l2_info(sd, "Stopped: %s\n",
> (i2c_rd16(sd, CSI_STATUS) & MASK_S_HLT) ?
> "yes" : "no");
> - v4l2_info(sd, "Color space: %s\n",
> - state->mbus_fmt_code == MEDIA_BUS_FMT_UYVY8_1X16 ?
> - "YCbCr 422 16-bit" :
> - state->mbus_fmt_code == MEDIA_BUS_FMT_RGB888_1X24 ?
> - "RGB 888 24-bit" : "Unsupported");
> +
> + switch (state->mbus_fmt_code) {
> + case MEDIA_BUS_FMT_BGR888_1X24:
> + /*
> + * The driver was initially introduced with RGB888
> + * support, but CSI really means BGR.
> + *
> + * Since we might have applications that would have
> + * hard-coded the RGB888, let's support both.
> + */
> + fallthrough;
> + case MEDIA_BUS_FMT_RGB888_1X24:
> + v4l2_info(sd, "Color space: BGR 888 24-bit\n");
> + break;
> + case MEDIA_BUS_FMT_UYVY8_1X16:
> + v4l2_info(sd, "Color space: YCbCr 422 16-bit\n");
> + break;
This has lost printing "Unsupported" if not one of the supported
formats, however I don't think there is a way for that to ever happen.
As it's not an enum, the compiler shouldn't be complaining of
unhandled values.
> + }
>
> v4l2_info(sd, "-----%s status-----\n", is_hdmi(sd) ? "HDMI" : "DVI-D");
> v4l2_info(sd, "HDCP encrypted content: %s\n",
> hdmi_sys_status & MASK_S_HDCP ? "yes" : "no");
> v4l2_info(sd, "Input color space: %s %s range\n",
> @@ -1695,24 +1718,33 @@ static int tc358743_enum_mbus_code(struct v4l2_subdev *sd,
> struct v4l2_subdev_state *sd_state,
> struct v4l2_subdev_mbus_code_enum *code)
> {
> switch (code->index) {
> case 0:
> - code->code = MEDIA_BUS_FMT_RGB888_1X24;
> + code->code = MEDIA_BUS_FMT_BGR888_1X24;
> break;
> case 1:
> code->code = MEDIA_BUS_FMT_UYVY8_1X16;
> break;
> + case 2:
> + /*
> + * We need to keep RGB888 for backward compatibility,
> + * but we should list it last for userspace to pick BGR.
> + */
> + code->code = MEDIA_BUS_FMT_RGB888_1X24;
> + break;
> default:
> return -EINVAL;
> }
> return 0;
> }
>
> static u32 tc358743_g_colorspace(u32 code)
> {
> switch (code) {
> + case MEDIA_BUS_FMT_BGR888_1X24:
> + fallthrough;
Do we need a fallthrough when there is no extra code between the two cases?
Otherwise it looks good to me.
Dave
> case MEDIA_BUS_FMT_RGB888_1X24:
> return V4L2_COLORSPACE_SRGB;
> case MEDIA_BUS_FMT_UYVY8_1X16:
> return V4L2_COLORSPACE_SMPTE170M;
> default:
> @@ -1746,11 +1778,12 @@ static int tc358743_set_fmt(struct v4l2_subdev *sd,
> struct tc358743_state *state = to_state(sd);
>
> u32 code = format->format.code; /* is overwritten by get_fmt */
> int ret = tc358743_get_fmt(sd, sd_state, format);
>
> - if (code == MEDIA_BUS_FMT_RGB888_1X24 ||
> + if (code == MEDIA_BUS_FMT_BGR888_1X24 ||
> + code == MEDIA_BUS_FMT_RGB888_1X24 ||
> code == MEDIA_BUS_FMT_UYVY8_1X16)
> format->format.code = code;
> format->format.colorspace = tc358743_g_colorspace(format->format.code);
>
> if (ret)
> @@ -2166,11 +2199,11 @@ static int tc358743_probe(struct i2c_client *client)
> sd->entity.function = MEDIA_ENT_F_VID_IF_BRIDGE;
> err = media_entity_pads_init(&sd->entity, 1, &state->pad);
> if (err < 0)
> goto err_hdl;
>
> - state->mbus_fmt_code = MEDIA_BUS_FMT_RGB888_1X24;
> + state->mbus_fmt_code = MEDIA_BUS_FMT_BGR888_1X24;
>
> sd->dev = &client->dev;
>
> mutex_init(&state->confctl_mutex);
>
>
> --
> 2.50.1
>
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