x86/platform/intel_mid_pci: Rework IRQ0 workaround

On Intel Merrifield platform several PCI devices have a bogus configuration,
i.e. the IRQ0 had been assigned to few of them. These are PCI root bridge,
eMMC0, HS UART common registers, PWM, and HDMI. The actual interrupt line can
be allocated to one device exclusively, in our case to eMMC0, the rest should
cope without it and basically known drivers for them are not using interrupt
line at all.

Rework IRQ0 workaround, which was previously done to avoid conflict between
eMMC0 and HS UART common registers, to behave differently based on the device
in question, i.e. allocate interrupt line to eMMC0, but silently skip interrupt
allocation for the rest except HS UART common registers which are not used
anyway. With this rework IOSF MBI driver in particular would be used.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Fixes: 39d9b77 ("x86/pci/intel_mid_pci: Work around for IRQ0 assignment")
Link: http://lkml.kernel.org/r/1465842481-136852-1-git-send-email-andriy.shevchenko@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/pci/intel_mid_pci.c

@@ -37,6 +37,7 @@
 
 /* Quirks for the listed devices */
 #define PCI_DEVICE_ID_INTEL_MRFL_MMC	0x1190
+#define PCI_DEVICE_ID_INTEL_MRFL_HSU	0x1191
 
 /* Fixed BAR fields */
 #define PCIE_VNDR_CAP_ID_FIXED_BAR 0x00	/* Fixed BAR (TBD) */
@@ -224,14 +225,21 @@ static int intel_mid_pci_irq_enable(struct pci_dev *dev)
 
 		/* Special treatment for IRQ0 */
 		if (dev->irq == 0) {
+			/*
+			 * Skip HS UART common registers device since it has
+			 * IRQ0 assigned and not used by the kernel.
+			 */
+			if (dev->device == PCI_DEVICE_ID_INTEL_MRFL_HSU)
+				return -EBUSY;
 			/*
 			 * TNG has IRQ0 assigned to eMMC controller. But there
 			 * are also other devices with bogus PCI configuration
 			 * that have IRQ0 assigned. This check ensures that
-			 * eMMC gets it.
+			 * eMMC gets it. The rest of devices still could be
+			 * enabled without interrupt line being allocated.
 			 */
 			if (dev->device != PCI_DEVICE_ID_INTEL_MRFL_MMC)
-				return -EBUSY;
+				return 0;
 		}
 		break;
 	default: