Commit 0fc6f44d authored by Russell King's avatar Russell King
Browse files

drm/i2c: tda998x: re-implement "Fix EDID read timeout on HDMI connect" 



Commit 6833d26e ("drm: tda998x: Fix EDID read timeout on HDMI
connect") used a weak scheme to try and delay reading EDID on a HDMI
connect event.  It is weak because delaying the notification of a
hotplug event does not stop userspace from trying to read the EDID
within the 100ms delay.

The solution provided here solves this issue:
* When a HDMI connection event is detected, mark a blocking flag for
  EDID reads, and start a timer for the delay.
* If an EDID read is attempted, and the blocking flag is set, wait
  for the blocking flag to clear.
* When the timer expires, clear the blocking flag and wake any thread
  waiting for the EDID read.

Signed-off-by: default avatarRussell King <rmk+kernel@arm.linux.org.uk>
parent f84a97d4

drivers/gpu/drm/i2c/tda998x_drv.c

+68 −12
Original line number Diff line number Diff line
@@ -34,7 +34,6 @@ struct tda998x_priv { 
	struct i2c_client *cec;

	struct i2c_client *hdmi;

	struct mutex mutex;

	struct delayed_work dwork;

	uint16_t rev;

	uint8_t current_page;

	int dpms;
@@ -47,6 +46,11 @@ struct tda998x_priv { 
	wait_queue_head_t wq_edid;

	volatile int wq_edid_wait;

	struct drm_encoder *encoder;



	struct work_struct detect_work;

	struct timer_list edid_delay_timer;

	wait_queue_head_t edid_delay_waitq;

	bool edid_delay_active;

};



#define to_tda998x_priv(x)  ((struct tda998x_priv *)to_encoder_slave(x)->slave_priv)
@@ -551,15 +555,50 @@ tda998x_reset(struct tda998x_priv *priv) 
	reg_write(priv, REG_MUX_VP_VIP_OUT, 0x24);

}



/* handle HDMI connect/disconnect */

static void tda998x_hpd(struct work_struct *work)

/*

 * The TDA998x has a problem when trying to read the EDID close to a

 * HPD assertion: it needs a delay of 100ms to avoid timing out while

 * trying to read EDID data.

 *

 * However, tda998x_encoder_get_modes() may be called at any moment

 * after tda998x_encoder_detect() indicates that we are connected, so

 * we need to delay probing modes in tda998x_encoder_get_modes() after

 * we have seen a HPD inactive->active transition.  This code implements

 * that delay.

 */

static void tda998x_edid_delay_done(unsigned long data)

{

	struct tda998x_priv *priv = (struct tda998x_priv *)data;



	priv->edid_delay_active = false;

	wake_up(&priv->edid_delay_waitq);

	schedule_work(&priv->detect_work);

}



static void tda998x_edid_delay_start(struct tda998x_priv *priv)

{

	priv->edid_delay_active = true;

	mod_timer(&priv->edid_delay_timer, jiffies + HZ/10);

}



static int tda998x_edid_delay_wait(struct tda998x_priv *priv)

{

	return wait_event_killable(priv->edid_delay_waitq, !priv->edid_delay_active);

}



/*

 * We need to run the KMS hotplug event helper outside of our threaded

 * interrupt routine as this can call back into our get_modes method,

 * which will want to make use of interrupts.

 */

static void tda998x_detect_work(struct work_struct *work)

{

	struct delayed_work *dwork = to_delayed_work(work);

	struct tda998x_priv *priv =

			container_of(dwork, struct tda998x_priv, dwork);

		container_of(work, struct tda998x_priv, detect_work);

	struct drm_device *dev = priv->encoder->dev;



	if (priv->encoder->dev)

		drm_kms_helper_hotplug_event(priv->encoder->dev);

	if (dev)

		drm_kms_helper_hotplug_event(dev);

}



/*
@@ -585,7 +624,11 @@ static irqreturn_t tda998x_irq_thread(int irq, void *data) 
		wake_up(&priv->wq_edid);

		handled = true;

	} else if (cec != 0) {			/* HPD change */

		schedule_delayed_work(&priv->dwork, HZ/10);

		if (lvl & CEC_RXSHPDLEV_HPD)

			tda998x_edid_delay_start(priv);

		else

			schedule_work(&priv->detect_work);



		handled = true;

	}

	return IRQ_RETVAL(handled);
@@ -1103,6 +1146,14 @@ tda998x_encoder_get_modes(struct tda998x_priv *priv, 
	struct edid *edid;

	int n;



	/*

	 * If we get killed while waiting for the HPD timeout, return

	 * no modes found: we are not in a restartable path, so we

	 * can't handle signals gracefully.

	 */

	if (tda998x_edid_delay_wait(priv))

		return 0;



	if (priv->rev == TDA19988)

		reg_clear(priv, REG_TX4, TX4_PD_RAM);
@@ -1149,10 +1200,12 @@ static void tda998x_destroy(struct tda998x_priv *priv) 
	/* disable all IRQs and free the IRQ handler */

	cec_write(priv, REG_CEC_RXSHPDINTENA, 0);

	reg_clear(priv, REG_INT_FLAGS_2, INT_FLAGS_2_EDID_BLK_RD);

	if (priv->hdmi->irq) {



	if (priv->hdmi->irq)

		free_irq(priv->hdmi->irq, priv);

		cancel_delayed_work_sync(&priv->dwork);

	}



	del_timer_sync(&priv->edid_delay_timer);

	cancel_work_sync(&priv->detect_work);



	i2c_unregister_device(priv->cec);

}
@@ -1253,6 +1306,10 @@ static int tda998x_create(struct i2c_client *client, struct tda998x_priv *priv) 
	priv->dpms = DRM_MODE_DPMS_OFF;



	mutex_init(&priv->mutex);	/* protect the page access */

	init_waitqueue_head(&priv->edid_delay_waitq);

	setup_timer(&priv->edid_delay_timer, tda998x_edid_delay_done,

		    (unsigned long)priv);

	INIT_WORK(&priv->detect_work, tda998x_detect_work);



	/* wake up the device: */

	cec_write(priv, REG_CEC_ENAMODS,
@@ -1311,7 +1368,6 @@ static int tda998x_create(struct i2c_client *client, struct tda998x_priv *priv) 


		/* init read EDID waitqueue and HDP work */

		init_waitqueue_head(&priv->wq_edid);

		INIT_DELAYED_WORK(&priv->dwork, tda998x_hpd);



		/* clear pending interrupts */

		reg_read(priv, REG_INT_FLAGS_0);

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