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

[Alexander Stein <alexander.stein@ew.tq-group.com>]

Hi,

Am Donnerstag, 13. Juli 2023, 00:34:47 CEST schrieb Tim Harvey:
> On Wed, May 3, 2023 at 9:33 AM Frieder Schrempf <frieder@fris.de> wrote:
> > From: Frieder Schrempf <frieder.schrempf@kontron.de>
> > 
> > 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-operatio
> > n
> > 
> > Signed-off-by: Frieder Schrempf <frieder.schrempf@kontron.de>
> > ---
> > 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 tested this with imx8mm and ti,sn65dsi83 DSI-LVDS bridge [1]. I don't know 
anything about tc358762, but I was trying to get tc9595 (DSI-DP bridge) 
running on a imx8mp based board. One of my problems was that the bridge 
requires LP-11 before reset release, which is currently not given using 
samsung-dsim and tc358767 driver. Maybe this is the case for you as well.
AFAICS there is a lot more to do to get this running properly.

Best regards,
Alexander

[1] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/
arch/arm64/boot/dts/freescale/imx8mp-tqma8mpql-mba8mpxl-lvds.dtso

> best regards,
> 
> Tim
> [1]
> https://patchwork.kernel.org/project/linux-arm-kernel/patch/20230711221124.
> 2127186-1-tharvey@gateworks.com/


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