[PATCH] drm/panel: ilitek-ili9881c: Avoid unbalance prepare/unprepare
Dave Stevenson
dave.stevenson at raspberrypi.com
Fri Dec 10 15:47:54 UTC 2021
Hi Michael
On Fri, 10 Dec 2021 at 09:05, Michael Nazzareno Trimarchi
<michael at amarulasolutions.com> wrote:
>
> Hi Dave
>
> some questions below
>
> On Thu, Dec 9, 2021 at 7:10 PM Michael Nazzareno Trimarchi
> <michael at amarulasolutions.com> wrote:
> >
> > Hi Dave
> >
> > On Thu, Dec 9, 2021 at 6:58 PM Dave Stevenson
> > <dave.stevenson at raspberrypi.com> wrote:
> > >
> > > Hi Michael
> > >
> > > On Thu, 9 Dec 2021 at 16:58, Michael Nazzareno Trimarchi
> > > <michael at amarulasolutions.com> wrote:
> > > >
> > > > Hi all
> > > >
> > > > On Sat, Oct 16, 2021 at 4:58 PM Michael Trimarchi
> > > > <michael at amarulasolutions.com> wrote:
> > > > >
> > > > > All the panel driver check the fact that their prepare/unprepare
> > > > > call was already called. It's not an ideal solution but fix
> > > > > for now the problem on ili9881c
> > > > >
> > > > > [ 9862.283296] ------------[ cut here ]------------
> > > > > [ 9862.288490] unbalanced disables for vcc3v3_lcd
> > > > > [ 9862.293555] WARNING: CPU: 0 PID: 1 at drivers/regulator/core.c:2851
> > > > > _regulator_disable+0xd4/0x190
> > > > >
> > > > > from:
> > > > >
> > > > > [ 9862.038619] drm_panel_unprepare+0x2c/0x4c
> > > > > [ 9862.043212] panel_bridge_post_disable+0x18/0x24
> > > > > [ 9862.048390] dw_mipi_dsi_bridge_post_disable+0x3c/0xf0
> > > > > [ 9862.054153] drm_atomic_bridge_chain_post_disable+0x8c/0xd0
> > > > >
> > > > > and:
> > > > >
> > > > > [ 9862.183103] drm_panel_unprepare+0x2c/0x4c
> > > > > [ 9862.187695] panel_bridge_post_disable+0x18/0x24
> > > > > [ 9862.192872] drm_atomic_bridge_chain_post_disable+0x8c/0xd0
> > > > > [ 9862.199117] disable_outputs+0x120/0x31c
> > >
> > > This is down to the dw-mipi-dsi driver calling the post_disable hook
> > > explicitly at [1], but then also allowing the framework to call it.
> > > The explicit call is down to limitations in the DSI support, so we
> > > can't control the DSI host state to a fine enough degree (an ongoing
> > > discussion [2] [3]). There shouldn't be a need to handle mismatched
> > > calling in individual panel drivers.
> > >
> > > Dave
> > >
> > > [1] https://github.com/torvalds/linux/blob/master/drivers/gpu/drm/bridge/synopsys/dw-mipi-dsi.c#L894
> > > [2] https://lists.freedesktop.org/archives/dri-devel/2021-November/332060.html
> > > [3] https://lists.freedesktop.org/archives/dri-devel/2021-December/334007.html
> >
> > I'm in the second case. I need to enable HS mode after the panel is
> > initialized. Time to time I have timeout
> > on dsi command or I have wrong panel initialization. So I explicit call from
> > the bridge but I understand that is not correct in the design point of view.
> >
> > So this patch can not be queued because it's a known problem that
> > people are discussing
> >
> Author: Michael Trimarchi <michael at amarulasolutions.com>
> Date: Thu Dec 9 15:45:48 2021 +0100
>
> drm: bridge: samsung-dsim: Enable panel/bridge before exist from standby
>
> We need to exist from standby as last operation to have a proper video
> working. This code implement the same code was before the bridge
> migration
>
> Signed-off-by: Michael Trimarchi <michael at amarulasolutions.com>
>
> diff --git a/drivers/gpu/drm/bridge/samsung-dsim.c
> b/drivers/gpu/drm/bridge/samsung-dsim.c
> index 654851edbd9b..21265ae80022 100644
> --- a/drivers/gpu/drm/bridge/samsung-dsim.c
> +++ b/drivers/gpu/drm/bridge/samsung-dsim.c
> @@ -1838,6 +1838,7 @@ 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);
> + struct drm_atomic_state old_state;
> int ret;
>
> if (dsi->state & DSIM_STATE_ENABLED)
> @@ -1859,6 +1860,9 @@ static void samsung_dsim_atomic_enable(struct
> drm_bridge *bridge,
> }
>
> samsung_dsim_set_display_mode(dsi);
> +
> + drm_atomic_bridge_chain_enable(dsi->out_bridge, &old_state);
Calling this is contrary to the documentation [1]
"Note: the bridge passed should be the one closest to the encoder"
You're passing in a bridge that is half way down the chain, from a
bridge atomic_enable that is already being called by
drm_atomic_bridge_chain_enable
[1] https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/drm_bridge.c#L695
> +
> samsung_dsim_set_display_enable(dsi, true);
>
> dsi->state |= DSIM_STATE_VIDOUT_AVAILABLE;
>
> Right now I'm doing this to enable the change. I must change the panel
> to avoid double enabled
>
> I have some questions:
>
> - the chain is an element (bridge/panel) linked together via some
> connector (I hope I understand) when I enable
> a bridge chain, all the elements should move from some status to
> another. If we mark them already this should
> not avoid that one element can be enabled two times? An element that
> sources two other elements should for instance
> receive the enable from two times before switching on.
I don't claim to be an expert, just that I've been trying to get DSI
working on a number of devices.
The bridge chain is meant to be managed by the framework via
drm_atomic_helper_commit_modeset_enables and
drm_atomic_helper_commit_modeset_disables calling the
drm_atomic_bridge_chain_* functions.
As documented, the framework calls the bridge pre_enable hooks
following the chain from connector towards the encoder, enables the
encoder, and then calls the enable hooks from bridge closest to the
encoder towards the connector. A similar approach applies for bridge
disable hooks, disable the encoder, and then bridge post_disable
hooks.
There should be no need to make any calls outside of that framework.
Doing so is what is causing these problems.
As Laurent summarised it in [2]:
"I can't agree more with Dave about the need for documentation, DSI
drivers (both on the TX and RX side) are very creative these days,
causing lots of interoperability issues. This wild west situation really
needs some policing."
I acknowledge that there is a failing in the framework for DSI, and
I've previously raised the question of how to best address this, but
all suggestions have largely been shot down with no alternatives
suggested.
I won't say that this patch can't be merged, but merging it and
ignoring the cause is admitting defeat.
Dave
[2] https://lists.freedesktop.org/archives/dri-devel/2021-December/334007.html
> Michael
>
> > Michael
> >
> > >
> > >
> > > > > Signed-off-by: Michael Trimarchi <michael at amarulasolutions.com>
> > > > > ---
> > > > > drivers/gpu/drm/panel/panel-ilitek-ili9881c.c | 14 ++++++++++++++
> > > > > 1 file changed, 14 insertions(+)
> > > > >
> > > > > diff --git a/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c b/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c
> > > > > index 103a16018975..f75eecb0e65c 100644
> > > > > --- a/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c
> > > > > +++ b/drivers/gpu/drm/panel/panel-ilitek-ili9881c.c
> > > > > @@ -52,6 +52,8 @@ struct ili9881c {
> > > > >
> > > > > struct regulator *power;
> > > > > struct gpio_desc *reset;
> > > > > +
> > > > > + bool prepared;
> > > > > };
> > > > >
> > > >
> > > > I found that this can be a general problem. Should not mandatory to
> > > > track panel status
> > > >
> > > > DRM_PANEL_PREPARED
> > > > DRM_PANEL_ENABLED
> > > >
> > > > Michael
> > > > > #define ILI9881C_SWITCH_PAGE_INSTR(_page) \
> > > > > @@ -707,6 +709,10 @@ static int ili9881c_prepare(struct drm_panel *panel)
> > > > > unsigned int i;
> > > > > int ret;
> > > > >
> > > > > + /* Preparing when already prepared is a no-op */
> > > > > + if (ctx->prepared)
> > > > > + return 0;
> > > > > +
> > > > > /* Power the panel */
> > > > > ret = regulator_enable(ctx->power);
> > > > > if (ret)
> > > > > @@ -745,6 +751,8 @@ static int ili9881c_prepare(struct drm_panel *panel)
> > > > > if (ret)
> > > > > return ret;
> > > > >
> > > > > + ctx->prepared = true;
> > > > > +
> > > > > return 0;
> > > > > }
> > > > >
> > > > > @@ -770,10 +778,16 @@ static int ili9881c_unprepare(struct drm_panel *panel)
> > > > > {
> > > > > struct ili9881c *ctx = panel_to_ili9881c(panel);
> > > > >
> > > > > + /* Unpreparing when already unprepared is a no-op */
> > > > > + if (!ctx->prepared)
> > > > > + return 0;
> > > > > +
> > > > > mipi_dsi_dcs_enter_sleep_mode(ctx->dsi);
> > > > > regulator_disable(ctx->power);
> > > > > gpiod_set_value(ctx->reset, 1);
> > > > >
> > > > > + ctx->prepared = false;
> > > > > +
> > > > > return 0;
> > > > > }
> > > > >
> > > > > --
> > > > > 2.25.1
> > > > >
> > > >
> > > >
> > > > --
> > > > Michael Nazzareno Trimarchi
> > > > Co-Founder & Chief Executive Officer
> > > > M. +39 347 913 2170
> > > > michael at amarulasolutions.com
> > > > __________________________________
> > > >
> > > > Amarula Solutions BV
> > > > Joop Geesinkweg 125, 1114 AB, Amsterdam, NL
> > > > T. +31 (0)85 111 9172
> > > > info at amarulasolutions.com
> > > > www.amarulasolutions.com
> >
> >
> >
> > --
> > Michael Nazzareno Trimarchi
> > Co-Founder & Chief Executive Officer
> > M. +39 347 913 2170
> > michael at amarulasolutions.com
> > __________________________________
> >
> > Amarula Solutions BV
> > Joop Geesinkweg 125, 1114 AB, Amsterdam, NL
> > T. +31 (0)85 111 9172
> > info at amarulasolutions.com
> > www.amarulasolutions.com
>
>
>
> --
> Michael Nazzareno Trimarchi
> Co-Founder & Chief Executive Officer
> M. +39 347 913 2170
> michael at amarulasolutions.com
> __________________________________
>
> Amarula Solutions BV
> Joop Geesinkweg 125, 1114 AB, Amsterdam, NL
> T. +31 (0)85 111 9172
> info at amarulasolutions.com
> www.amarulasolutions.com
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