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

[Herve Codina <herve.codina@bootlin.com>]

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@bootlin.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);
+
+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 pipeline\n");
+
+	/* Reset the pipeline */
+	ret = sn65dsi83_reset_pipeline(ctx);
+	if (ret) {
+		dev_err(ctx->dev, "reset pipeline 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);
+}
+
+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)
 {
@@ -509,6 +601,15 @@ 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,
@@ -517,6 +618,15 @@ 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);
@@ -673,6 +783,14 @@ 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);
@@ -686,6 +804,8 @@ static int sn65dsi83_probe(struct i2c_client *client)
 		return -ENOMEM;
 
 	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)
@@ -710,6 +830,14 @@ 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);
 
-- 
2.46.2