Re: [PATCH v3 3/3] drm: bridge: ti-sn65dsi83: Add error recovery mechanism

Alexander Stein
2025-01-08T10:55:01Z

Hi Herve,

Am Mittwoch, 8. Januar 2025, 11:19:02 CET schrieb Herve Codina:
> 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.
>
> Also, during tests, cases were observed where reading the status of the
> bridge was not even possible. Indeed, in those cases, the bridge stops
> to acknowledge I2C transactions. Only a full reset of the bridge (power
> off/on) brings back the bridge to a functional state.
>
> 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 or when reading
> the bridge status leads to an I2C failure, 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 whole
> output path (i.e the path from the encoder to the connector) where the
> bridge is located.
>
> Signed-off-by: Herve Codina <herve.codina@bootlin.com>
> ---
> drivers/gpu/drm/bridge/ti-sn65dsi83.c | 147 ++++++++++++++++++++++++++
> 1 file changed, 147 insertions(+)
>
> diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi83.c b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
> index e6264514bb3f..74bc05647436 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() needs drm_drv_uses_atomic_modeset() */

Shouldn't this include be added to include/drm/drm_modeset_lock.h instead?

> #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;

Can you please rebase? You are missing commit d2b8c6d549570
("drm/bridge: ti-sn65dsi83: Add ti,lvds-vod-swing optional properties")

> };
>
> static const struct regmap_range sn65dsi83_readable_ranges[] = {
> @@ -328,6 +334,111 @@ static u8 sn65dsi83_get_dsi_div(struct sn65dsi83 *ctx)
> return dsi_div - 1;
> }
>
> +static int sn65dsi83_reset_pipe(struct sn65dsi83 *sn65dsi83)
> +{
> + struct drm_atomic_state *state = ERR_PTR(-EINVAL);
> + struct drm_device *dev = sn65dsi83->bridge.dev;
> + struct drm_connector_state *connector_state;
> + struct drm_modeset_acquire_ctx ctx;
> + struct drm_connector *connector;
> + int err;
> +
> + /*
> + * Reset active outputs of the related CRTC.
> + *
> + * This way, drm core will reconfigure each components in the CRTC
> + * outputs path. In our case, this will force the previous component to
> + * go back in LP11 mode and so allow the reconfiguration of SN64DSI83
> + * bridge.
> + *
> + * Keep the lock during the whole operation to be atomic.
> + */
> +
> + 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;
> + }
> +
> + state->acquire_ctx = &ctx;
> +
> + connector = drm_atomic_get_old_connector_for_encoder(state,
> + sn65dsi83->bridge.encoder);
> + if (!connector) {
> + err = -EINVAL;
> + goto unlock;
> + }
> +
> + connector_state = drm_atomic_get_connector_state(state, connector);
> + if (IS_ERR(connector_state)) {
> + err = PTR_ERR(connector_state);
> + goto unlock;
> + }
> +
> + err = drm_atomic_helper_reset_pipe(connector_state->crtc, &ctx);
> + if (err < 0)
> + goto unlock;
> +
> +unlock:
> + DRM_MODESET_LOCK_ALL_END(dev, ctx, err);
> + if (!IS_ERR(state))
> + drm_atomic_state_put(state);
> + return err;
> +}
> +
> +static void sn65dsi83_reset_work(struct work_struct *ws)
> +{
> + struct sn65dsi83 *ctx = container_of(ws, struct sn65dsi83, reset_work);
> + int ret;
> +
> + dev_warn(ctx->dev, "reset the pipe\n");
> +
> + /* Reset the pipe */
> + ret = sn65dsi83_reset_pipe(ctx);
> + if (ret) {
> + dev_err(ctx->dev, "reset pipe failed %pe\n", ERR_PTR(ret));
> + return;
> + }
> +}
> +
> +static void sn65dsi83_handle_errors(struct sn65dsi83 *ctx)
> +{
> + unsigned int irq_stat;
> + int ret;
> +
> + /*
> + * Schedule a reset in case of:
> + * - the bridge doesn't answer
> + * - the bridge signals an error
> + */
> +
> + ret = regmap_read(ctx->regmap, REG_IRQ_STAT, &irq_stat);
> + if (ret || irq_stat)
> + schedule_work(&ctx->reset_work);

Shouldn't you clear the error bits as well?

Best regards,
Alexander

> +}
> +
> +static void sn65dsi83_monitor_work(struct work_struct *work)
> +{
> + struct sn65dsi83 *ctx = container_of(to_delayed_work(work),
> + struct sn65dsi83, monitor_work);
> +
> + sn65dsi83_handle_errors(ctx);
> +
> + schedule_delayed_work(&ctx->monitor_work, msecs_to_jiffies(1000));
> +}
> +
> +static void sn65dsi83_monitor_start(struct sn65dsi83 *ctx)
> +{
> + schedule_delayed_work(&ctx->monitor_work, msecs_to_jiffies(1000));
> +}
> +
> +static void sn65dsi83_monitor_stop(struct sn65dsi83 *ctx)
> +{
> + cancel_delayed_work_sync(&ctx->monitor_work);
> +}
> +
> static void sn65dsi83_atomic_pre_enable(struct drm_bridge *bridge,
> struct drm_bridge_state *old_bridge_state)
> {
> @@ -516,6 +627,15 @@ static void sn65dsi83_atomic_enable(struct drm_bridge *bridge,
> regmap_read(ctx->regmap, REG_IRQ_STAT, &pval);
> if (pval)
> dev_err(ctx->dev, "Unexpected link status 0x%02x\n", pval);
> +
> + if (ctx->use_irq) {
> + /* Enable irq to detect errors */
> + regmap_write(ctx->regmap, REG_IRQ_GLOBAL, REG_IRQ_GLOBAL_IRQ_EN);
> + regmap_write(ctx->regmap, REG_IRQ_EN, 0xff);
> + } else {
> + /* Use the polling task */
> + sn65dsi83_monitor_start(ctx);
> + }
> }
>
> static void sn65dsi83_atomic_disable(struct drm_bridge *bridge,
> @@ -524,6 +644,15 @@ static void sn65dsi83_atomic_disable(struct drm_bridge *bridge,
> struct sn65dsi83 *ctx = bridge_to_sn65dsi83(bridge);
> int ret;
>
> + if (ctx->use_irq) {
> + /* Disable irq */
> + regmap_write(ctx->regmap, REG_IRQ_EN, 0x0);
> + regmap_write(ctx->regmap, REG_IRQ_GLOBAL, 0x0);
> + } else {
> + /* Stop the polling task */
> + sn65dsi83_monitor_stop(ctx);
> + }
> +
> /* Put the chip in reset, pull EN line low, and assure 10ms reset low timing. */
> gpiod_set_value_cansleep(ctx->enable_gpio, 0);
> usleep_range(10000, 11000);
> @@ -681,6 +810,14 @@ static int sn65dsi83_host_attach(struct sn65dsi83 *ctx)
> return 0;
> }
>
> +static irqreturn_t sn65dsi83_irq(int irq, void *data)
> +{
> + struct sn65dsi83 *ctx = data;
> +
> + sn65dsi83_handle_errors(ctx);
> + return IRQ_HANDLED;
> +}
> +
> static int sn65dsi83_probe(struct i2c_client *client)
> {
> const struct i2c_device_id *id = i2c_client_get_device_id(client);
> @@ -698,6 +835,8 @@ static int sn65dsi83_probe(struct i2c_client *client)
> return ret;
>
> ctx->dev = dev;
> + INIT_WORK(&ctx->reset_work, sn65dsi83_reset_work);
> + INIT_DELAYED_WORK(&ctx->monitor_work, sn65dsi83_monitor_work);
>
> if (dev->of_node) {
> model = (enum sn65dsi83_model)(uintptr_t)
> @@ -722,6 +861,14 @@ static int sn65dsi83_probe(struct i2c_client *client)
> if (IS_ERR(ctx->regmap))
> return dev_err_probe(dev, PTR_ERR(ctx->regmap), "failed to get regmap\n");
>
> + if (client->irq) {
> + ret = devm_request_threaded_irq(ctx->dev, client->irq, NULL, sn65dsi83_irq,
> + IRQF_ONESHOT, dev_name(ctx->dev), ctx);
> + if (ret)
> + return dev_err_probe(dev, ret, "failed to request irq\n");
> + ctx->use_irq = true;
> + }
> +
> dev_set_drvdata(dev, ctx);
> i2c_set_clientdata(client, ctx);
>
>

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