PCI: disable ASPM on pre-1.1 PCIe devices

Disable ASPM on pre-1.1 PCIe devices, as many of them don't implement it
correctly.

Tested-by: Jack Howarth <[e-mail]>
Signed-off-by: Shaohua Li <[e-mail]>
Signed-off-by: Jesse Barnes <[e-mail]>

drivers/pci/pcie/aspm.c

···
 {
 	struct pci_dev *child_dev;
 	int child_pos;
+	u32 reg32;
 
 	/*
 	 * Some functions in a slot might not all be PCIE functions, very
···
 		child_pos = pci_find_capability(child_dev, PCI_CAP_ID_EXP);
 		if (!child_pos)
 			return -EINVAL;
+
+		/*
+		 * Disable ASPM for pre-1.1 PCIe device, we follow MS to use
+		 * RBER bit to determine if a function is 1.1 version device
+		 */
+		pci_read_config_dword(child_dev, child_pos + PCI_EXP_DEVCAP,
+			&reg32);
+		if (!(reg32 & PCI_EXP_DEVCAP_RBER)) {
+			printk("Pre-1.1 PCIe device detected, "
+				"disable ASPM for %s\n", pci_name(pdev));
+			return -EINVAL;
+		}
 	}
 	return 0;
 }

drivers/pci/probe.c

···
 		}
 	}
 
-	if (bus->self)
+	/* only one slot has pcie device */
+	if (bus->self && nr)
 		pcie_aspm_init_link_state(bus->self);
 
 	return nr;

include/linux/pci_regs.h

···
 #define  PCI_EXP_DEVCAP_ATN_BUT	0x1000	/* Attention Button Present */
 #define  PCI_EXP_DEVCAP_ATN_IND	0x2000	/* Attention Indicator Present */
 #define  PCI_EXP_DEVCAP_PWR_IND	0x4000	/* Power Indicator Present */
+#define  PCI_EXP_DEVCAP_RBER	0x8000	/* Role-Based Error Reporting */
 #define  PCI_EXP_DEVCAP_PWR_VAL	0x3fc0000 /* Slot Power Limit Value */
 #define  PCI_EXP_DEVCAP_PWR_SCL	0xc000000 /* Slot Power Limit Scale */
 #define PCI_EXP_DEVCTL		8	/* Device Control */