From: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
To: Alexander Stein <alexander.stein@ew.tq-group.com>
Cc: Andrzej Hajda <andrzej.hajda@intel.com>,
Neil Armstrong <neil.armstrong@linaro.org>,
Robert Foss <rfoss@kernel.org>,
Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
Jonas Karlman <jonas@kwiboo.se>,
Jernej Skrabec <jernej.skrabec@gmail.com>,
Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
Maxime Ripard <mripard@kernel.org>,
Thomas Zimmermann <tzimmermann@suse.de>,
David Airlie <airlied@gmail.com>,
Daniel Vetter <daniel@ffwll.ch>,
Chun-Kuang Hu <chunkuang.hu@kernel.org>,
Philipp Zabel <p.zabel@pengutronix.de>,
Matthias Brugger <matthias.bgg@gmail.com>,
AngeloGioacchino Del Regno
<angelogioacchino.delregno@collabora.com>,
Sam Ravnborg <sam@ravnborg.org>,
Vinay Simha BN <simhavcs@gmail.com>,
Tony Lindgren <tony@atomide.com>,
dri-devel@lists.freedesktop.org,
Michael Walle <mwalle@kernel.org>,
Daniel Semkowicz <dse@thaumatec.com>,
linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH 01/20] drm/bridge: add dsi_lp11_notify mechanism
Date: Tue, 7 May 2024 16:39:27 +0300 [thread overview]
Message-ID: <577v55mspa672t2bqbwwvdtfdgtbj6mpejo3n56qk7bt2j6bt3@q54dfnupcvs4> (raw)
In-Reply-To: <2189493.irdbgypaU6@steina-w>
On Tue, May 07, 2024 at 10:37:54AM +0200, Alexander Stein wrote:
> Hi Michael,
>
> Am Montag, 6. Mai 2024, 15:34:30 CEST schrieb Michael Walle:
> > Some bridges have very strict power-up reqirements. In this case, the
> > Toshiba TC358775. The reset has to be deasserted while *both* the DSI
> > clock and DSI data lanes are in LP-11 mode. After the reset is relased,
> > the bridge needs the DSI clock to actually be able to process I2C
> > access. This access will configure the DSI side of the bridge during
> > which the DSI data lanes have to be in LP-11 mode.
>
> Apparently this is an issue for a lot of DSI bridges. But enabling LP-11 for
> a bridge is impossible with current documentation [1], which states "A DSI
> host should keep the PHY powered down until the pre_enable operation is
> called."
> Additionally tc358767/tc9595 (DSI-DP bridge) needs LP-11 for AUX channel
> access to even get EDID. This is a requirement before pre_enable would
> even be possible.
>
> So some changes to the current flow are needed. But I am not so sure
> about LP-11 notification. IMHO a device request to the DSI host to
> enable LP-11 seems more sensible.
Granted that there can be several DSI devices sharing the DSI bus (aka
split-link), I was toying with the idea of making the DSI host call
attached DSI devices when the transition happens.
I don't have a fully working PoC and I probably won't have it ready til
the end of May because of the lack of time and different local
priorities.
>
> Best regards,
> Alexander
>
> [1] https://www.kernel.org/doc/html/latest/gpu/drm-kms-helpers.html#mipi-dsi-bridge-operation
>
> > After everything is
> > configured the video stream can finally be enabled.
> >
> > This means:
> > (1) The bridge has to be configured completely in .pre_enable() op
> > (with the clock turned on and data lanes in LP-11 mode, thus
> > .pre_enable_prev_first has to be set).
> > (2) The bridge will enable its output in the .enable() op
> > (3) There must be some mechanism before (1) where the bridge can
> > release its reset while the clock lane is still in LP-11 mode.
> >
> > Unfortunately, (3) is crucial for a correct operation of the bridge.
> > To satisfy this requriment, introduce a new callback .dsi_lp11_notify()
> > which will be called by the DSI host driver.
> >
> > Signed-off-by: Michael Walle <mwalle@kernel.org>
> > ---
> > drivers/gpu/drm/drm_bridge.c | 16 ++++++++++++++++
> > include/drm/drm_bridge.h | 12 ++++++++++++
> > 2 files changed, 28 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> > index 28abe9aa99ca..98cd6558aecb 100644
> > --- a/drivers/gpu/drm/drm_bridge.c
> > +++ b/drivers/gpu/drm/drm_bridge.c
> > @@ -1339,6 +1339,22 @@ void drm_bridge_hpd_notify(struct drm_bridge *bridge,
> > }
> > EXPORT_SYMBOL_GPL(drm_bridge_hpd_notify);
> >
> > +/**
> > + * drm_bridge_dsi_lp11_notify - notify clock/data lanes LP-11 mode
> > + * @bridge: bridge control structure
> > + *
> > + * DSI host drivers shall call this function while the clock and data lanes
> > + * are still in LP-11 mode.
> > + *
> > + * This function shall be called in a context that can sleep.
> > + */
> > +void drm_bridge_dsi_lp11_notify(struct drm_bridge *bridge)
> > +{
> > + if (bridge->funcs->dsi_lp11_notify)
> > + bridge->funcs->dsi_lp11_notify(bridge);
> > +}
> > +EXPORT_SYMBOL_GPL(drm_bridge_dsi_lp11_notify);
> > +
> > #ifdef CONFIG_OF
> > /**
> > * of_drm_find_bridge - find the bridge corresponding to the device node in
> > diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> > index 4baca0d9107b..4ef61274e0a8 100644
> > --- a/include/drm/drm_bridge.h
> > +++ b/include/drm/drm_bridge.h
> > @@ -630,6 +630,17 @@ struct drm_bridge_funcs {
> > */
> > void (*hpd_disable)(struct drm_bridge *bridge);
> >
> > + /**
> > + * dsi_lp11_notify:
> > + *
> > + * Will be called by the DSI host driver while both the DSI clock
> > + * lane as well as the DSI data lanes are in LP-11 mode. Some bridges
> > + * need this state while releasing the reset, for example.
> > + * Not all DSI host drivers will support this. Therefore, the DSI
> > + * bridge driver must not rely on this op to be called.
> > + */
> > + void (*dsi_lp11_notify)(struct drm_bridge *bridge);
> > +
> > /**
> > * @debugfs_init:
> > *
> > @@ -898,6 +909,7 @@ void drm_bridge_hpd_enable(struct drm_bridge *bridge,
> > void drm_bridge_hpd_disable(struct drm_bridge *bridge);
> > void drm_bridge_hpd_notify(struct drm_bridge *bridge,
> > enum drm_connector_status status);
> > +void drm_bridge_dsi_lp11_notify(struct drm_bridge *bridge);
> >
> > #ifdef CONFIG_DRM_PANEL_BRIDGE
> > bool drm_bridge_is_panel(const struct drm_bridge *bridge);
> >
> >
>
>
> --
> TQ-Systems GmbH | Mühlstraße 2, Gut Delling | 82229 Seefeld, Germany
> Amtsgericht München, HRB 105018
> Geschäftsführer: Detlef Schneider, Rüdiger Stahl, Stefan Schneider
> http://www.tq-group.com/
>
>
--
With best wishes
Dmitry
next prev parent reply other threads:[~2024-05-07 13:39 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-05-06 13:34 [PATCH 00/20] drm/bridge: tc358775: proper bridge bringup and code cleanup Michael Walle
2024-05-06 13:34 ` [PATCH 01/20] drm/bridge: add dsi_lp11_notify mechanism Michael Walle
2024-05-07 8:37 ` Alexander Stein
2024-05-07 13:39 ` Dmitry Baryshkov [this message]
2024-05-06 13:34 ` [PATCH 02/20] drm/mediatek: dsi: provide LP-11 mode during .pre_enable Michael Walle
2024-05-06 13:34 ` [PATCH 03/20] drm/mediatek: dsi: add support for .dsi_lp11_notity() Michael Walle
2024-05-06 13:34 ` [PATCH 04/20] drm/bridge: tc358775: fix regulator supply id Michael Walle
2024-05-06 13:34 ` [PATCH 05/20] drm/bridge: tc358775: add crtc modes fixup Michael Walle
2024-05-06 13:34 ` [PATCH 06/20] drm/bridge: tc358775: redefine LV_MX() Michael Walle
2024-05-06 13:34 ` [PATCH 07/20] drm/bridge: tc358775: use regmap instead of open coded access functions Michael Walle
2024-05-06 13:34 ` [PATCH 08/20] drm/bridge: tc358775: remove error message if regulator is missing Michael Walle
2024-05-06 13:34 ` [PATCH 09/20] drm/bridge: tc358775: remove complex vsdelay calculation Michael Walle
2024-05-06 13:34 ` [PATCH 10/20] drm/bridge: tc358775: simplify lvds_link property Michael Walle
2024-05-06 13:34 ` [PATCH 11/20] drm/bridge: tc358775: reformat weird indentation Michael Walle
2024-05-06 13:34 ` [PATCH 12/20] drm/bridge: tc358775: correctly configure LVDS clock Michael Walle
2024-05-06 13:34 ` [PATCH 13/20] drm/bridge: tc358775: split the init code Michael Walle
2024-05-06 13:34 ` [PATCH 14/20] drm/bridge: tc358775: configure PLL depending on the LVDS clock Michael Walle
2024-05-06 13:34 ` [PATCH 15/20] drm/bridge: tc358775: dynamically configure DSI link settings Michael Walle
2024-05-06 13:34 ` [PATCH 16/20] drm/bridge: tc358775: use proper defines to configure LVDS timings Michael Walle
2024-05-06 13:34 ` [PATCH 17/20] drm/bridge: tc358775: move bridge power up/down into functions Michael Walle
2024-05-06 13:34 ` [PATCH 18/20] drm/bridge: tc358775: fix the power-up/down delays Michael Walle
2024-05-06 13:34 ` [PATCH 19/20] drm/bridge: tc358775: fix power-up sequencing Michael Walle
2024-05-06 13:34 ` [PATCH 20/20] drm/bridge: tc358775: use devm_drm_bridge_add() Michael Walle
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