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

["Andy Yan" <andyshrk@163.com>]

Hi all，

At 2024-10-28 00:23:50, "Laurent Pinchart" <laurent.pinchart@ideasonboard.com> 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@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);
>
>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?


>
>> +
>> +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);
>>  
>
>-- 
>Regards,
>
>Laurent Pinchart