[REGRESSION] i915: No HDMI output with 4.4

[Ville Syrjälä]

On Thu, Feb 11, 2016 at 01:16:53PM +0200, Oleksandr Natalenko wrote:
> Ville,
> 
> here is another dmesg: [1]
> 
> I've reconnected HDMI cable three times.
> 
> Forgot to note, it is HDMI monitor plugged into machine's DVI with 
> HDMI-DVI cable. I guess this should matter as well.

Shouldn't really matter. HDMI and DVI are identical at this level.

> 
> [1] https://gist.github.com/7057ea8512b9aa7ee5bd

OK, so the hpd interrupt does happen, and yet the live status supposedly
claims that nothing is there. Port C live status definitely works here
on my IVB, so not sure what the deal is.

Can you grab intel-gpu-tools and run
intel_reg read 0xc4000 0xc4004 0xc4008 0xc400c 0xc4030
a couple of times after plugging the monitor in, and also run it when
nothing is plugged in.

Also you could try something like the following patch so we might
observe the live status with a bit more detail. Though the fact that it
doesn't seem to work for you even when the monitor was already plugged
in is somewhat troubling:

--- a/drivers/gpu/drm/i915/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/intel_hdmi.c
@@ -1392,12 +1392,17 @@ intel_hdmi_detect(struct drm_connector *connector, bool force)
 
 	intel_display_power_get(dev_priv, POWER_DOMAIN_GMBUS);
 
-	for (try = 0; !live_status && try < 9; try++) {
-		if (try)
-			msleep(10);
-		live_status = intel_digital_port_connected(dev_priv,
+	printk("port %c live status\n ", port_name(hdmi_to_dig_port(intel_hdmi)->port));
+	for (try = 0; try < 250; try++) {
+		bool status = intel_digital_port_connected(dev_priv,
 				hdmi_to_dig_port(intel_hdmi));
+		live_status |= status;
+		printk("%c", status ? '#' : '_');
+		if (try % 50 == 49)
+			printk("\n ");
+		usleep_range(1000, 1000);
 	}
+	printk("\n");
 
 	if (!live_status)
 		DRM_DEBUG_KMS("Live status not up!");
-- 
2.4.10

Oh, and if you have another cable you can try, might be a good idea to
see if it behaves any better.

> 
> 11.02.2016 11:26, Ville Syrjälä написав:
> > On Thu, Feb 11, 2016 at 10:54:08AM +0200, Oleksandr Natalenko wrote:
> >> Daniel,
> >> 
> >> I've already tried Ville's patch you've mentioned with no luck.
> >> 
> >> Kindly find unpatched v4.5-rc3 dmesg with drm debug enabled here: [1]
> >> 
> >> [1] https://gist.github.com/efb44b7c6bc325978b80
> > 
> > That's an IVB. So no wonder my patch doesn't help.
> > 
> > Can you grab another dmesg after disconnecting and reconnecting the
> > HDMI cable?

-- 
Ville Syrjälä
Intel OTC