linux-kernel - Re: [PATCH 2/2] drm: bridge: ti-sn65dsi83: Add error recovery mechanism

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20241028-thankful-boar-of-camouflage-3de96c@houat>
Date: Mon, 28 Oct 2024 10:16:38 +0100
From: Maxime Ripard <mripard@...nel.org>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: Herve Codina <herve.codina@...tlin.com>, 
	Andrzej Hajda <andrzej.hajda@...el.com>, Neil Armstrong <neil.armstrong@...aro.org>, 
	Robert Foss <rfoss@...nel.org>, Jonas Karlman <jonas@...boo.se>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, David Airlie <airlied@...il.com>, 
	Simona Vetter <simona@...ll.ch>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Thomas Zimmermann <tzimmermann@...e.de>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, Marek Vasut <marex@...x.de>, 
	dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	Luca Ceresoli <luca.ceresoli@...tlin.com>, Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH 2/2] drm: bridge: ti-sn65dsi83: Add error recovery
 mechanism

On Sun, Oct 27, 2024 at 06:23:50PM +0200, Laurent Pinchart wrote:
> On Thu, Oct 24, 2024 at 11:55:38AM +0200, Herve Codina wrote:
> > In some cases observed during ESD tests, the TI SN65DSI83 cannot recover
> > from errors by itself. A full restart of the bridge is needed in those
> > cases to have the bridge output LVDS signals again.
> > 
> > The TI SN65DSI83 has some error detection capabilities. Introduce an
> > error recovery mechanism based on this detection.
> > 
> > The errors detected are signaled through an interrupt. On system where
> > this interrupt is not available, the driver uses a polling monitoring
> > fallback to check for errors. When an error is present, the recovery
> > process is launched.
> > 
> > Restarting the bridge needs to redo the initialization sequence. This
> > initialization sequence has to be done with the DSI data lanes driven in
> > LP11 state. In order to do that, the recovery process resets the entire
> > pipeline.
> > 
> > Signed-off-by: Herve Codina <herve.codina@...tlin.com>
> > ---
> >  drivers/gpu/drm/bridge/ti-sn65dsi83.c | 128 ++++++++++++++++++++++++++
> >  1 file changed, 128 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi83.c b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
> > index 96e829163d87..22975b60e80f 100644
> > --- a/drivers/gpu/drm/bridge/ti-sn65dsi83.c
> > +++ b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
> > @@ -35,9 +35,12 @@
> >  #include <linux/of_graph.h>
> >  #include <linux/regmap.h>
> >  #include <linux/regulator/consumer.h>
> > +#include <linux/timer.h>
> > +#include <linux/workqueue.h>
> >  
> >  #include <drm/drm_atomic_helper.h>
> >  #include <drm/drm_bridge.h>
> > +#include <drm/drm_drv.h> /* DRM_MODESET_LOCK_ALL_BEGIN() need drm_drv_uses_atomic_modeset() */
> >  #include <drm/drm_mipi_dsi.h>
> >  #include <drm/drm_of.h>
> >  #include <drm/drm_panel.h>
> > @@ -147,6 +150,9 @@ struct sn65dsi83 {
> >  	struct regulator		*vcc;
> >  	bool				lvds_dual_link;
> >  	bool				lvds_dual_link_even_odd_swap;
> > +	bool				use_irq;
> > +	struct delayed_work		monitor_work;
> > +	struct work_struct		reset_work;
> >  };
> >  
> >  static const struct regmap_range sn65dsi83_readable_ranges[] = {
> > @@ -321,6 +327,92 @@ static u8 sn65dsi83_get_dsi_div(struct sn65dsi83 *ctx)
> >  	return dsi_div - 1;
> >  }
> >  
> > +static int sn65dsi83_reset_pipeline(struct sn65dsi83 *sn65dsi83)
> > +{
> > +	struct drm_device *dev = sn65dsi83->bridge.dev;
> > +	struct drm_modeset_acquire_ctx ctx;
> > +	struct drm_atomic_state *state;
> > +	int err;
> > +
> > +	/* Use operation done in drm_atomic_helper_suspend() followed by
> > +	 * operation done in drm_atomic_helper_resume() but without releasing
> > +	 * the lock between suspend()/resume()
> > +	 */
> > +
> > +	DRM_MODESET_LOCK_ALL_BEGIN(dev, ctx, 0, err);
> > +
> > +	state = drm_atomic_helper_duplicate_state(dev, &ctx);
> > +	if (IS_ERR(state)) {
> > +		err = PTR_ERR(state);
> > +		goto unlock;
> > +	}
> > +
> > +	err = drm_atomic_helper_disable_all(dev, &ctx);
> > +	if (err < 0)
> > +		goto unlock;
> > +
> > +	drm_mode_config_reset(dev);
> > +
> > +	err = drm_atomic_helper_commit_duplicated_state(state, &ctx);
> 
> Committing a full atomic state from a bridge driver in an asynchronous
> way seems quite uncharted territory, and it worries me. It's also a very
> heavyweight, you disable all outputs here, instead of focussing on the
> output connected to the bridge. Can you either implement something more
> local, resetting the bridge only, or create a core helper to handle this
> kind of situation, on a per-output basis ?

I think you can't just shut down the bridge and restart it, since some
require particular power sequences that will only occur if you also shut
down the upstream controller.

So I think we'd need to tear down the CRTC, connector and everything
in between.

I do agree that it needs to be a generic helper though. In fact, it
looks awfully similar to what vc4 and i915 are doing in reset_pipe and
and intel_modeset_commit_pipes, respectively. It looks like a good
opportunity to make it a helper.

Maxime

Download attachment "signature.asc" of type "application/pgp-signature" (274 bytes)