Re: [PATCH v3 06/13] drm: bridge: samsung-dsim: Add DSI init in bridge pre_enable()

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

Hi Jagan and Marek.

On Fri, 22 Jul 2022 at 16:35, Marek Szyprowski <m.szyprowski@samsung.com> wrote:
>
> On 20.07.2022 17:52, Jagan Teki wrote:
> > Host transfer() in DSI master will invoke only when the DSI commands
> > are sent from DSI devices like DSI Panel or DSI bridges and this
> > host transfer wouldn't invoke for I2C-based-DSI bridge drivers.
> >
> > Handling DSI host initialization in transfer calls misses the
> > controller setup for I2C configured DSI bridges.
> >
> > This patch adds the DSI initialization from transfer to bridge
> > pre_enable as the bridge pre_enable API is invoked by core as
> > it is common across all classes of DSI device drivers.
>
> This is still problematic in case of Exynos. Without a workaround like this
>
> https://github.com/mszyprow/linux/commit/11bbfc61272da9610dd5c574bb8ef838dc150961
>
> the display on the all real DSI panels on my Exynos based boards is broken.

I'd queried on the other thread trying to address DSI operation [1] as
to whether the test for STOP_STATE (presumably LP-11) at [2] was
actually valid, but had no response.
There is no need to check for bus contention at that point, but should
it happen the driver doesn't write the registers in lines 862-868
having returned -EFAULT at line 853. The controller is therefore only
partially initialised.

I may be misinterpreting what that code is waiting for though, or the
hardware may require some further state before it can be initialised.

  Dave

[1] https://www.mail-archive.com/dri-devel@lists.freedesktop.org/msg397703.html
[2] https://github.com/mszyprow/linux/blob/11bbfc61272da9610dd5c574bb8ef838dc150961/drivers/gpu/drm/bridge/samsung-dsim.c#L850

> >
> > v3:
> > * none
> >
> > v2:
> > * check initialized state in samsung_dsim_init
> >
> > v1:
> > * keep DSI init in host transfer
> >
> > Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
> > ---
> >   drivers/gpu/drm/bridge/samsung-dsim.c | 18 ++++++++++++------
> >   1 file changed, 12 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
> > index 9b74a3f98a17..b07909a52f2d 100644
> > --- a/drivers/gpu/drm/bridge/samsung-dsim.c
> > +++ b/drivers/gpu/drm/bridge/samsung-dsim.c
> > @@ -1258,6 +1258,9 @@ static int samsung_dsim_init(struct samsung_dsim *dsi)
> >   {
> >       const struct samsung_dsim_driver_data *driver_data = dsi->driver_data;
> >
> > +     if (dsi->state & DSIM_STATE_INITIALIZED)
> > +             return 0;
> > +
> >       samsung_dsim_reset(dsi);
> >       samsung_dsim_enable_irq(dsi);
> >
> > @@ -1270,6 +1273,8 @@ static int samsung_dsim_init(struct samsung_dsim *dsi)
> >       samsung_dsim_set_phy_ctrl(dsi);
> >       samsung_dsim_init_link(dsi);
> >
> > +     dsi->state |= DSIM_STATE_INITIALIZED;
> > +
> >       return 0;
> >   }
> >
> > @@ -1289,6 +1294,10 @@ static void samsung_dsim_atomic_pre_enable(struct drm_bridge *bridge,
> >       }
> >
> >       dsi->state |= DSIM_STATE_ENABLED;
> > +
> > +     ret = samsung_dsim_init(dsi);
> > +     if (ret)
> > +             return;
> >   }
> >
> >   static void samsung_dsim_atomic_enable(struct drm_bridge *bridge,
> > @@ -1464,12 +1473,9 @@ static ssize_t samsung_dsim_host_transfer(struct mipi_dsi_host *host,
> >       if (!(dsi->state & DSIM_STATE_ENABLED))
> >               return -EINVAL;
> >
> > -     if (!(dsi->state & DSIM_STATE_INITIALIZED)) {
> > -             ret = samsung_dsim_init(dsi);
> > -             if (ret)
> > -                     return ret;
> > -             dsi->state |= DSIM_STATE_INITIALIZED;
> > -     }
> > +     ret = samsung_dsim_init(dsi);
> > +     if (ret)
> > +             return ret;
> >
> >       ret = mipi_dsi_create_packet(&xfer.packet, msg);
> >       if (ret < 0)
>
> Best regards
> --
> Marek Szyprowski, PhD
> Samsung R&D Institute Poland
>