[PATCH V2 2/2] drm/bridge: ti-sn65dsi83: Add TI SN65DSI83 and SN65DSI84 driver

[Jagan Teki]

On Wed, Apr 28, 2021 at 2:54 PM Neil Armstrong <narmstrong at baylibre.com> wrote:
>
> On 28/04/2021 11:26, Loic Poulain wrote:
> > On Wed, 28 Apr 2021 at 10:13, Frieder Schrempf
> > <frieder.schrempf at kontron.de> wrote:
> >>
> >> On 28.04.21 09:51, Frieder Schrempf wrote:
> >>> On 22.04.21 00:31, Marek Vasut wrote:
> >>>> Add driver for TI SN65DSI83 Single-link DSI to Single-link LVDS bridge
> >>>> and TI SN65DSI84 Single-link DSI to Dual-link or 2x Single-link LVDS
> >>>> bridge. TI SN65DSI85 is unsupported due to lack of hardware to test on,
> >>>> but easy to add.
> >>>>
> >>>> The driver operates the chip via I2C bus. Currently the LVDS clock are
> >>>> always derived from DSI clock lane, which is the usual mode of operation.
> >>>> Support for clock from external oscillator is not implemented, but it is
> >>>> easy to add if ever needed. Only RGB888 pixel format is implemented, the
> >>>> LVDS666 is not supported, but could be added if needed.
> >>>>
> >>>> Signed-off-by: Marek Vasut <marex at denx.de>
> >>>> Cc: Douglas Anderson <dianders at chromium.org>
> >>>> Cc: Jagan Teki <jagan at amarulasolutions.com>
> >>>> Cc: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> >>>> Cc: Linus Walleij <linus.walleij at linaro.org>
> >>>> Cc: Philippe Schenker <philippe.schenker at toradex.com>
> >>>> Cc: Sam Ravnborg <sam at ravnborg.org>
> >>>> Cc: Stephen Boyd <swboyd at chromium.org>
> >>>> Cc: Valentin Raevsky <valentin at compulab.co.il>
> >>>> To: dri-devel at lists.freedesktop.org
> >>>> Tested-by: Loic Poulain <loic.poulain at linaro.org>
> >>>> ---
> >>>> V2: - Use dev_err_probe()
> >>>>      - Set REG_RC_RESET as volatile
> >>>>      - Wait for PLL stabilization by polling REG_RC_LVDS_PLL
> >>>>      - Use ctx->mode = *adj instead of *mode in sn65dsi83_mode_set
> >>>>      - Add tested DSI84 support in dual-link mode
> >>>>      - Correctly set VCOM
> >>>>      - Fill in missing DSI CHB and LVDS CHB bits from DSI84 and DSI85
> >>>>        datasheets, with that all the reserved bits make far more sense
> >>>>        as the DSI83 and DSI84 seems to be reduced version of DSI85
> >>>> ---
> >>>>   drivers/gpu/drm/bridge/Kconfig        |  10 +
> >>>>   drivers/gpu/drm/bridge/Makefile       |   1 +
> >>>>   drivers/gpu/drm/bridge/ti-sn65dsi83.c | 617 ++++++++++++++++++++++++++
> >>>>   3 files changed, 628 insertions(+)
> >>>>   create mode 100644 drivers/gpu/drm/bridge/ti-sn65dsi83.c
> >>>>
> >>> [...]
> >>>> +static int sn65dsi83_probe(struct i2c_client *client,
> >>>> +               const struct i2c_device_id *id)
> >>>> +{
> >>>> +    struct device *dev = &client->dev;
> >>>> +    enum sn65dsi83_model model;
> >>>> +    struct sn65dsi83 *ctx;
> >>>> +    int ret;
> >>>> +
> >>>> +    ctx = devm_kzalloc(dev, sizeof(*ctx), GFP_KERNEL);
> >>>> +    if (!ctx)
> >>>> +        return -ENOMEM;
> >>>> +
> >>>> +    ctx->dev = dev;
> >>>> +
> >>>> +    if (dev->of_node)
> >>>> +        model = (enum sn65dsi83_model)of_device_get_match_data(dev);
> >>>> +    else
> >>>> +        model = id->driver_data;
> >>>> +
> >>>> +    /* Default to dual-link LVDS on all but DSI83. */
> >>>> +    if (model != MODEL_SN65DSI83)
> >>>> +        ctx->lvds_dual_link = true;
> >>>
> >>> What if I use the DSI84 with a single link LVDS? I can't see any way to
> >>> configure that right now.
> >
> > I assume the simplest way would be to use the "ti,sn65dsi83"
> > compatible string in your dts, since the way you wired it is
> > 'compatible' with sn65dsi83, right?
>
> No this isn't the right way to to, if sn65dsi84 is supported and the bindings only support single lvds link,
> the driver must only support single link on sn65dsi84, or add the dual link lvds in the bindings only for sn65dsi84.
>
> >
> >>
> >> I just saw the note in the header of the driver that says that single
> >> link mode is unsupported for the DSI84.
> >>
> >> I have hardware with a single link display and if I set
> >> ctx->lvds_dual_link = false it works just fine.
> >>
> >> How is this supposed to be selected? Does it need an extra devicetree
> >> property? And would you mind adding single-link support in the next
> >> version or do you prefer adding it in a follow-up patch?
> >
> > If this has to be supported I think the proper way would be to support
> > two output ports in the dts (e.g. lvds0_out, lvds1_out), in the same
> > way as supported by the 'advantech,idk-2121wr' panel.
>
> Yes, this is why I asked to have the dual-link lvds in the bindings.

Agreed with Neil, this is what we discussed on my v3. Each of these 3
chips has its own compatible and supporting dual-link lvds and
dual-link dsi as to be done by 84/85 and 85 respectively.

Maybe I can push my configuration changes in gist if required?

Jagan.