Re: [PATCH v5 4/4] drm: bridge: ti-sn65dsi83: Add error recovery mechanism

Alexander Stein
2025-02-06T14:38:59Z

Hi,

Am Montag, 3. Februar 2025, 17:16:06 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>
> ---

With interrupt configured I got the following stack trace upon
reboot/poweroff:

[ 91.317264] sn65dsi83 2-002d: reset the pipe
[ 91.344093] Unable to handle ke
** replaying previous printk message **
[ 91.344093] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
[ 91.344107] Mem abort info:
[ 91.344111] ESR = 0x0000000096000004
[ 91.344115] EC = 0x25: DABT (current EL), IL = 32 bits
[ 91.344120] SET = 0, FnV = 0
[ 91.344122] EA = 0, S1PTW = 0
[ 91.344125] FSC = 0x04: level 0 translation fault
[ 91.344128] Data abort info:
[ 91.344130] ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000
[ 91.344133] CM = 0, WnR = 0, TnD = 0, TagAccess = 0
[ 91.344136] GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
[ 91.344141] user pgtable: 4k pages, 48-bit VAs, pgdp=0000000102eec000
[ 91.344145] [0000000000000000] pgd=0000000000000000, p4d=0000000000000000
[ 91.344155] Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP
[ 91.420670] Modules linked in: bluetooth 8021q garp mrp stp llc hid_generic hantro_vpu snd_soc_fsl_asoc_card snd_soc_fsl_sai snd_soc_imx_audmux snd_soc_t
lv320aic32x4_i2c imx_pcm_dma v4l2_vp9 snd_soc_simple_card_utils snd_soc_tlv320aic32x4 snd_soc_fsl_utils v4l2_h264 v4l2_jpeg snd_soc_core videobuf2_dma_conti
g v4l2_mem2mem videobuf2_memops videobuf2_v4l2 snd_pcm_dmaengine videobuf2_common imx8m_ddrc phy_generic snd_pcm ci_hdrc_imx ti_sn65dsi83 ci_hdrc clk_renesa
s_pcie mxsfb snd_timer samsung_dsim usbmisc_imx pwm_imx27 snd soundcore spi_imx imx_sdma imx8mm_thermal panel_simple gpio_aggregator pwm_beeper cfg80211 rfk
ill fuse ipv6
[ 91.476291] CPU: 0 UID: 0 PID: 83 Comm: kworker/0:3 Not tainted 6.14.0-rc1-next-20250205+ #2906 da26d4e444ec7c54f82096af1ee2c91e843e9303
[ 91.488555] Hardware name: TQ-Systems GmbH i.MX8MM TQMa8MxML on MBa8Mx (DT)
[ 91.495517] Workqueue: events sn65dsi83_reset_work [ti_sn65dsi83]
[ 91.501623] pstate: 60000005 (nZCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ 91.508588] pc : drm_atomic_helper_reset_crtc+0x18/0x100
[ 91.513906] lr : sn65dsi83_reset_work+0x80/0x118 [ti_sn65dsi83]
[ 91.519832] sp : ffff80008271bcc0
[ 91.523146] x29: ffff80008271bcc0 x28: 0000000000000000 x27: 0000000000000000
[ 91.530288] x26: ffff0000c0d6e340 x25: 0000000000000000 x24: ffff0000c0022005
[ 91.537432] x23: ffff0000c4cb4248 x22: ffff0000ff736e40 x21: ffff80008271bcf8
[ 91.544576] x20: 0000000000000000 x19: 0000000000000000 x18: 0000000000000000
[ 91.551719] x17: 000000040044ffff x16: 0000000000000000 x15: 00000015425993c0
[ 91.558860] x14: 0000000000000001 x13: ffff0000c0ece800 x12: 0000000000000020
[ 91.566004] x11: ffff0000c0ece800 x10: 0000000000000af0 x9 : ffff80008271ba70
[ 91.573147] x8 : ffff0000c0ecf2d0 x7 : ffff0000c0ece800 x6 : dead000000000122
[ 91.580291] x5 : 0000000000000000 x4 : ffff0000c0ece780 x3 : 0000000000000000
[ 91.587436] x2 : ffff0000c4cb40b8 x1 : ffff80008271bcf8 x0 : 0000000000000000
[ 91.594580] Call trace:
[ 91.597027] drm_atomic_helper_reset_crtc+0x18/0x100 (P)
[ 91.602346] sn65dsi83_reset_work+0x80/0x118 [ti_sn65dsi83 d96dc31a1413a92a7c205a475a2357ddacaa4a3b]
[ 91.611485] process_one_work+0x14c/0x3e0
[ 91.615503] worker_thread+0x2d0/0x3f0
[ 91.619257] kthread+0x110/0x1e0
[ 91.622488] ret_from_fork+0x10/0x20
[ 91.626073] Code: a90153f3 aa0003f4 f90013f5 aa0103f5 (f9400000)
[ 91.632167] ---[ end trace 0000000000000000 ]---

Running with workqueue does not raise this error.

Best regards,
Alexander

> drivers/gpu/drm/bridge/ti-sn65dsi83.c | 131 ++++++++++++++++++++++++++
> 1 file changed, 131 insertions(+)
>
> diff --git a/drivers/gpu/drm/bridge/ti-sn65dsi83.c b/drivers/gpu/drm/bridge/ti-sn65dsi83.c
> index 336380114eea..26a050b13997 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() */
> #include <drm/drm_mipi_dsi.h>
> #include <drm/drm_of.h>
> #include <drm/drm_panel.h>
> @@ -159,6 +162,9 @@ struct sn65dsi83 {
> bool lvds_dual_link_even_odd_swap;
> int lvds_vod_swing_conf[2];
> int lvds_term_conf[2];
> + int irq;
> + struct delayed_work monitor_work;
> + struct work_struct reset_work;
> };
>
> static const struct regmap_range sn65dsi83_readable_ranges[] = {
> @@ -363,6 +369,95 @@ static u8 sn65dsi83_get_dsi_div(struct sn65dsi83 *ctx)
> return dsi_div - 1;
> }
>
> +static int sn65dsi83_reset_pipe(struct sn65dsi83 *sn65dsi83)
> +{
> + struct drm_device *dev = sn65dsi83->bridge.dev;
> + struct drm_modeset_acquire_ctx ctx;
> + 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);
> +
> + err = drm_atomic_helper_reset_crtc(sn65dsi83->bridge.encoder->crtc, &ctx);
> +
> + DRM_MODESET_LOCK_ALL_END(dev, ctx, err);
> +
> + 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;
> + }
> + if (ctx->irq)
> + enable_irq(ctx->irq);
> +}
> +
> +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) {
> + /*
> + * IRQ acknowledged is not always possible (the bridge can be in
> + * a state where it doesn't answer anymore). To prevent an
> + * interrupt storm, disable interrupt. The interrupt will be
> + * after the reset.
> + */
> + if (ctx->irq)
> + disable_irq_nosync(ctx->irq);
> +
> + 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)
> {
> @@ -549,6 +644,15 @@ 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->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,
> @@ -557,6 +661,15 @@ static void sn65dsi83_atomic_disable(struct drm_bridge *bridge,
> struct sn65dsi83 *ctx = bridge_to_sn65dsi83(bridge);
> int ret;
>
> + if (ctx->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);
> @@ -806,6 +919,14 @@ 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);
> @@ -819,6 +940,8 @@ 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)
> @@ -843,6 +966,14 @@ 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) {
> + ctx->irq = client->irq;
> + ret = devm_request_threaded_irq(ctx->dev, ctx->irq, NULL, sn65dsi83_irq,
> + IRQF_ONESHOT, dev_name(ctx->dev), ctx);
> + if (ret)
> + return dev_err_probe(dev, ret, "failed to request irq\n");
> + }
> +
> dev_set_drvdata(dev, ctx);
> i2c_set_clientdata(client, ctx);
>
>

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