ALSA: hda - Check the dead HDMI audio controller by vga-switcheroo

When a discrete-GPU is disabled by the VGA switcheroo, the
corresponding HD-audio controller for HDMI output is also disabled.
Such a dead controller still appears in the PCI device list, but you
can't access properly any longer (even calling pci_read_config_*()
triggers Oops!) which leads the stall of the whole communication of
the driver.

This patch adds a check of graphics controller at the probe time to
see whether it's disabled by vga-switcheroo.  If disabled, skip the
whole initialization of this controller.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=43155

Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/hda/hda_intel.c

@@ -53,6 +53,7 @@
 #endif
 #include <sound/core.h>
 #include <sound/initval.h>
+#include <linux/vgaarb.h>
 #include "hda_codec.h"
 
 
@@ -2493,6 +2494,45 @@ static int azx_dev_free(struct snd_device *device)
 	return azx_free(device->device_data);
 }
 
+/*
+ * Check of disabled HDMI controller by vga-switcheroo
+ */
+static struct pci_dev __devinit *get_bound_vga(struct pci_dev *pci)
+{
+	struct pci_dev *p;
+
+	/* check only discrete GPU */
+	switch (pci->vendor) {
+	case PCI_VENDOR_ID_ATI:
+	case PCI_VENDOR_ID_AMD:
+	case PCI_VENDOR_ID_NVIDIA:
+		if (pci->devfn == 1) {
+			p = pci_get_domain_bus_and_slot(pci_domain_nr(pci->bus),
+							pci->bus->number, 0);
+			if (p) {
+				if ((p->class >> 8) == PCI_CLASS_DISPLAY_VGA)
+					return p;
+				pci_dev_put(p);
+			}
+		}
+		break;
+	}
+	return NULL;
+}
+
+static bool __devinit check_hdmi_disabled(struct pci_dev *pci)
+{
+	bool vga_inactive = false;
+	struct pci_dev *p = get_bound_vga(pci);
+
+	if (p) {
+		if (vga_default_device() && p != vga_default_device())
+			vga_inactive = true;
+		pci_dev_put(p);
+	}
+	return vga_inactive;
+}
+
 /*
  * white/black-listing for position_fix
  */
@@ -2928,6 +2968,12 @@ static int __devinit azx_probe(struct pci_dev *pci,
 		return -ENOENT;
 	}
 
+	if (check_hdmi_disabled(pci)) {
+		snd_printk(KERN_INFO SFX
+			   "Inactive VGA controller; disabled audio, too\n");
+		goto out;
+	}
+
 	err = snd_card_create(index[dev], id[dev], THIS_MODULE, 0, &card);
 	if (err < 0) {
 		snd_printk(KERN_ERR SFX "Error creating card!\n");
@@ -2984,16 +3030,20 @@ static int __devinit azx_probe(struct pci_dev *pci,
 	power_down_all_codecs(chip);
 	azx_notifier_register(chip);
 
+ out:
 	dev++;
-	return err;
+	return 0;
+
 out_free:
 	snd_card_free(card);
 	return err;
 }
 
 static void __devexit azx_remove(struct pci_dev *pci)
 {
-	snd_card_free(pci_get_drvdata(pci));
+	struct snd_card *card = pci_get_drvdata(pci);
+	if (card)
+		snd_card_free(card);
 	pci_set_drvdata(pci, NULL);
 }