On Tue, Oct 29, 2024 at 04:02:33PM +0800, Andy Yan wrote:
> At 2024-10-28 00:23:50, "Laurent Pinchart" <laurent.pinchart@xxxxxxxxxxxxxxxx> 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@xxxxxxxxxxx>
> >> ---
> >> 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 ?
>
> If we could simulate a hotplug（disconnected then connected） event to
> user space and let userspace do the disable/enable of the output
> pipeline, would things be simpler?
No, because you can't expect the userspace to handle that event in the
first place.
Maxime
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