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

[Loic Poulain]

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?

>
> 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.

Regards,
Loic