Re: [PATCH v2 1/2] drm: bridge: samsung-dsim: Fix i.MX8M enable flow to meet spec

[Adam Ford]

On Wed, Jul 12, 2023 at 5:34 PM Tim Harvey <tharvey@xxxxxxxxxxxxx> wrote:
>
> On Wed, May 3, 2023 at 9:33 AM Frieder Schrempf <frieder@xxxxxxx> wrote:
> >
> > From: Frieder Schrempf <frieder.schrempf@xxxxxxxxxx>
> >
> > According to the documentation [1] the proper enable flow is:
> >
> > 1. Enable DSI link and keep data lanes in LP-11 (stop state)
> > 2. Disable stop state to bring data lanes into HS mode
> >
> > Currently we do this all at once within enable(), which doesn't
> > allow to meet the requirements of some downstream bridges.
> >
> > To fix this we now enable the DSI in pre_enable() and force it
> > into stop state using the FORCE_STOP_STATE bit in the ESCMODE
> > register until enable() is called where we reset the bit.
> >
> > We currently do this only for i.MX8M as Exynos uses a different
> > init flow where samsung_dsim_init() is called from
> > samsung_dsim_host_transfer().
> >
> > [1] https://docs.kernel.org/gpu/drm-kms-helpers.html#mipi-dsi-bridge-operation
> >
> > Signed-off-by: Frieder Schrempf <frieder.schrempf@xxxxxxxxxx>
> > ---
> > Changes for v2:
> > * Drop RFC
> > ---
> >  drivers/gpu/drm/bridge/samsung-dsim.c | 25 +++++++++++++++++++++++--
> >  1 file changed, 23 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c b/drivers/gpu/drm/bridge/samsung-dsim.c
> > index e0a402a85787..9775779721d9 100644
> > --- a/drivers/gpu/drm/bridge/samsung-dsim.c
> > +++ b/drivers/gpu/drm/bridge/samsung-dsim.c
> > @@ -859,6 +859,10 @@ static int samsung_dsim_init_link(struct samsung_dsim *dsi)
> >         reg = samsung_dsim_read(dsi, DSIM_ESCMODE_REG);
> >         reg &= ~DSIM_STOP_STATE_CNT_MASK;
> >         reg |= DSIM_STOP_STATE_CNT(driver_data->reg_values[STOP_STATE_CNT]);
> > +
> > +       if (!samsung_dsim_hw_is_exynos(dsi->plat_data->hw_type))
> > +               reg |= DSIM_FORCE_STOP_STATE;
> > +
> >         samsung_dsim_write(dsi, DSIM_ESCMODE_REG, reg);
> >
> >         reg = DSIM_BTA_TIMEOUT(0xff) | DSIM_LPDR_TIMEOUT(0xffff);
> > @@ -1340,6 +1344,9 @@ static void samsung_dsim_atomic_pre_enable(struct drm_bridge *bridge,
> >                 ret = samsung_dsim_init(dsi);
> >                 if (ret)
> >                         return;
> > +
> > +               samsung_dsim_set_display_mode(dsi);
> > +               samsung_dsim_set_display_enable(dsi, true);
> >         }
> >  }
> >
> > @@ -1347,9 +1354,16 @@ static void samsung_dsim_atomic_enable(struct drm_bridge *bridge,
> >                                        struct drm_bridge_state *old_bridge_state)
> >  {
> >         struct samsung_dsim *dsi = bridge_to_dsi(bridge);
> > +       u32 reg;
> >
> > -       samsung_dsim_set_display_mode(dsi);
> > -       samsung_dsim_set_display_enable(dsi, true);
> > +       if (samsung_dsim_hw_is_exynos(dsi->plat_data->hw_type)) {
> > +               samsung_dsim_set_display_mode(dsi);
> > +               samsung_dsim_set_display_enable(dsi, true);
> > +       } else {
> > +               reg = samsung_dsim_read(dsi, DSIM_ESCMODE_REG);
> > +               reg &= ~DSIM_FORCE_STOP_STATE;
> > +               samsung_dsim_write(dsi, DSIM_ESCMODE_REG, reg);
> > +       }
> >
> >         dsi->state |= DSIM_STATE_VIDOUT_AVAILABLE;
> >  }
> > @@ -1358,10 +1372,17 @@ static void samsung_dsim_atomic_disable(struct drm_bridge *bridge,
> >                                         struct drm_bridge_state *old_bridge_state)
> >  {
> >         struct samsung_dsim *dsi = bridge_to_dsi(bridge);
> > +       u32 reg;
> >
> >         if (!(dsi->state & DSIM_STATE_ENABLED))
> >                 return;
> >
> > +       if (!samsung_dsim_hw_is_exynos(dsi->plat_data->hw_type)) {
> > +               reg = samsung_dsim_read(dsi, DSIM_ESCMODE_REG);
> > +               reg |= DSIM_FORCE_STOP_STATE;
> > +               samsung_dsim_write(dsi, DSIM_ESCMODE_REG, reg);
> > +       }
> > +
> >         dsi->state &= ~DSIM_STATE_VIDOUT_AVAILABLE;
> >  }
> >
> > --
> > 2.40.0
> >
>
> Hi Frieder,
>
> I found this patch to break mipi-dsi display on my board which has:
>  - FocalTech FT5406 10pt touch controller (with no interrupt)
>  - Powertip PH800480T013-IDF02 compatible panel
>  - Toshiba TC358762 compatible DSI to DBI bridge
>  - ATTINY based regulator used for backlight controller and panel enable
>
> I enable this via a dt overlay in a pending patch
> imx8mm-venice-gw72xx-0x-rpidsi.dtso [1] which works on 6.4 but not
> 6.5-rc1 which has this patch.
>
> The issue appears as:
> [    6.110585] samsung-dsim 32e60000.dsi: xfer timed out: 29 06 00 00
> 64 01 05 00 00 00
> [    6.326588] tc358762 32e60000.dsi.0: error initializing bridge (-110)
>
> Instead of
> [    1.011729] samsung-dsim 32e10000.dsi: supply vddcore not found,
> using dummy regulator
> [    1.019829] samsung-dsim 32e10000.dsi: supply vddio not found,
> using dummy regulator
> [    5.649928] samsung-dsim 32e10000.dsi:
> [drm:samsung_dsim_host_attach] Attached tc358762 device
>
> I'm curious what board/panel were you needing this for and do you have
> any ideas why it broke my setup?
>
> I'm also curious what board/panel Alexander tested this with and if
> Adam or Jagan (or others) have tested this with their hardware?

I have used the imx8mm and imx8mn with both an Analog Devices ADV7535
HDMI bridge, and a ti,sn65dsi83, and the imx8mp with the just the
adv7535.  I haven't seen any issues with this patch, but I wonder if
the downstream part for Tim needs to do something with this patch
installed, or whether or not we should add some sort of dsim flag that
either does this or skips it.  I would be curious to know if the NXP
downstream code works with either Frieder's or Tim's.

adam
>
> best regards,
>
> Tim
> [1] https://patchwork.kernel.org/project/linux-arm-kernel/patch/20230711221124.2127186-1-tharvey@xxxxxxxxxxxxx/