Re: [PATCH v3 3/3] drm/bridge/lontium-lt9611uxc: move HPD notification out of IRQ handler

Hi Dmitry,

W dniu 17.01.2021 o 01:23, Dmitry Baryshkov pisze:

drm hotplug handling code (drm_client_dev_hotplug()) can wait on mutex, thus delaying further lt9611uxc IRQ events processing. It was observed occasionally during bootups, when drm_client_modeset_probe() was waiting for EDID ready event, which was delayed because IRQ handler was stuck trying to deliver hotplug event. Move hotplug notifications from IRQ handler to separate work to be able to process IRQ events without delays.

Signed-off-by: Dmitry Baryshkov dmitry.baryshkov@linaro.org Fixes: 0cbbd5b1a012 ("drm: bridge: add support for lontium LT9611UXC bridge") Reviewed-by: Bjorn Andersson bjorn.andersson@linaro.org Signed-off-by: Dmitry Baryshkov dmitry.baryshkov@linaro.org

---

drivers/gpu/drm/bridge/lontium-lt9611uxc.c | 30 +++++++++++++++++----- 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/bridge/lontium-lt9611uxc.c b/drivers/gpu/drm/bridge/lontium-lt9611uxc.c index b708700e182d..209e39923914 100644 --- a/drivers/gpu/drm/bridge/lontium-lt9611uxc.c +++ b/drivers/gpu/drm/bridge/lontium-lt9611uxc.c @@ -14,6 +14,7 @@ #include <linux/regmap.h> #include <linux/regulator/consumer.h> #include <linux/wait.h> +#include <linux/workqueue.h>

#include <sound/hdmi-codec.h>

@@ -36,6 +37,7 @@ struct lt9611uxc { struct mutex ocm_lock;

struct wait_queue_head wq;

• struct work_struct work;

  struct device_node *dsi0_node; struct device_node *dsi1_node;

@@ -52,6 +54,7 @@ struct lt9611uxc {

bool hpd_supported; bool edid_read;

• bool hdmi_connected; uint8_t fw_version; };

@@ -151,15 +154,26 @@ static irqreturn_t lt9611uxc_irq_thread_handler(int irq, void *dev_id) }

if (irq_status & BIT(1)) {

• if (lt9611uxc->connector.dev)
  

• 	drm_kms_helper_hotplug_event(lt9611uxc->connector.dev);
  

• else
  

• 	drm_bridge_hpd_notify(&lt9611uxc->bridge, !!(hpd_status & BIT(1)));
  

• lt9611uxc->hdmi_connected = !!(hpd_status & BIT(1));
  

No need for !!, int->bool implicit conversion will do the thing.

• schedule_work(&lt9611uxc->work);
  

  }

  return IRQ_HANDLED; }

+static void lt9611uxc_hpd_work(struct work_struct *work) +{

• struct lt9611uxc *lt9611uxc = container_of(work, struct lt9611uxc, work);
• if (lt9611uxc->connector.dev)

• drm_kms_helper_hotplug_event(lt9611uxc->connector.dev);
  

• else

• drm_bridge_hpd_notify(&lt9611uxc->bridge,
  

• 		      lt9611uxc->hdmi_connected ?
  

• 		      connector_status_connected :
  

• 		      connector_status_disconnected);
  

I am little bit worried about accessing lt9611uxc->hdmi_connected - it is set in different thread, and there is no explicit sync code between them. I guess it is possible to loss proper HPD signal, especially if the HPD line is unstable (is there signal debouncing?).

+}

• static void lt9611uxc_reset(struct lt9611uxc *lt9611uxc) { gpiod_set_value_cansleep(lt9611uxc->reset_gpio, 1);

@@ -447,7 +461,7 @@ static enum drm_connector_status lt9611uxc_bridge_detect(struct drm_bridge *brid struct lt9611uxc *lt9611uxc = bridge_to_lt9611uxc(bridge); unsigned int reg_val = 0; int ret;

• int connected = 1;

• bool connected = true;

  if (lt9611uxc->hpd_supported) { lt9611uxc_lock(lt9611uxc);

@@ -457,8 +471,9 @@ static enum drm_connector_status lt9611uxc_bridge_detect(struct drm_bridge *brid if (ret) dev_err(lt9611uxc->dev, "failed to read hpd status: %d\n", ret); else

• 	connected  = reg_val & BIT(1);
  

• 	connected  = !!(reg_val & BIT(1));
  

Again no no need for !!.

I saw in v2 there was R-B tags added by Bjorn to other two patches, please do not forgot them next time.

Regards

Andrzej

}

• lt9611uxc->hdmi_connected = connected;

  return connected ? connector_status_connected : connector_status_disconnected;

@@ -931,6 +946,8 @@ static int lt9611uxc_probe(struct i2c_client *client, lt9611uxc->fw_version = ret;

init_waitqueue_head(&lt9611uxc->wq);

• INIT_WORK(&lt9611uxc->work, lt9611uxc_hpd_work);
• ret = devm_request_threaded_irq(dev, client->irq, NULL, lt9611uxc_irq_thread_handler, IRQF_ONESHOT, "lt9611uxc", lt9611uxc);

@@ -967,6 +984,7 @@ static int lt9611uxc_remove(struct i2c_client *client) struct lt9611uxc *lt9611uxc = i2c_get_clientdata(client);

disable_irq(client->irq);

• flush_scheduled_work(); lt9611uxc_audio_exit(lt9611uxc); drm_bridge_remove(&lt9611uxc->bridge);