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

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Commit 6833d26ef8 ("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: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Russell King 2015-06-06 21:41:09 +01:00
parent f84a97d480
commit 0fc6f44d96
1 changed files with 69 additions and 13 deletions
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82
drivers/gpu/drm/i2c/tda998x_drv.c
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@ -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 delayed_work *dwork = to_delayed_work(work);
struct tda998x_priv *priv =
container_of(dwork, struct tda998x_priv, dwork);
struct tda998x_priv *priv = (struct tda998x_priv *)data;
if (priv->encoder->dev)
drm_kms_helper_hotplug_event(priv->encoder->dev);
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 tda998x_priv *priv =
container_of(work, struct tda998x_priv, detect_work);
struct drm_device *dev = 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);