x86: Work around mmio config space quirk on AMD Fam10h

Some broken devices have been discovered to require %al/%ax/%eax registers
for MMIO config space accesses. Modify mmconfig.c to use these registers
explicitly (rather than modify the global readb/writeb/etc inlines).

AK: also changed i386 to always use eax
AK: moved change to extended space probing to different patch
AK: reworked with inlines according to Linus' requirements.
AK: improve comments.

Signed-off-by: dean gaudet <[e-mail]>
Signed-off-by: Andi Kleen <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

arch/i386/pci/mmconfig.c

···
 
 	switch (len) {
 	case 1:
-		*value = readb(mmcfg_virt_addr + reg);
+		*value = mmio_config_readb(mmcfg_virt_addr + reg);
 		break;
 	case 2:
-		*value = readw(mmcfg_virt_addr + reg);
+		*value = mmio_config_readw(mmcfg_virt_addr + reg);
 		break;
 	case 4:
-		*value = readl(mmcfg_virt_addr + reg);
+		*value = mmio_config_readl(mmcfg_virt_addr + reg);
 		break;
 	}
-
 	spin_unlock_irqrestore(&pci_config_lock, flags);
 
 	return 0;
···
 
 	switch (len) {
 	case 1:
-		writeb(value, mmcfg_virt_addr + reg);
+		mmio_config_writeb(mmcfg_virt_addr, value);
 		break;
 	case 2:
-		writew(value, mmcfg_virt_addr + reg);
+		mmio_config_writew(mmcfg_virt_addr, value);
 		break;
 	case 4:
-		writel(value, mmcfg_virt_addr + reg);
+		mmio_config_writel(mmcfg_virt_addr, value);
 		break;
 	}
-
 	spin_unlock_irqrestore(&pci_config_lock, flags);
 
 	return 0;

arch/i386/pci/pci.h

···
 extern int __init pci_mmcfg_arch_reachable(unsigned int seg, unsigned int bus,
 					   unsigned int devfn);
 extern int __init pci_mmcfg_arch_init(void);
+
+/*
+ * AMD Fam10h CPUs are buggy, and cannot access MMIO config space
+ * on their northbrige except through the * %eax register. As such, you MUST
+ * NOT use normal IOMEM accesses, you need to only use the magic mmio-config
+ * accessor functions.
+ * In fact just use pci_config_*, nothing else please.
+ */
+static inline unsigned char mmio_config_readb(void __iomem *pos)
+{
+	u8 val;
+	asm volatile("movb (%1),%%al" : "=a" (val) : "r" (pos));
+	return val;
+}
+
+static inline unsigned short mmio_config_readw(void __iomem *pos)
+{
+	u16 val;
+	asm volatile("movw (%1),%%ax" : "=a" (val) : "r" (pos));
+	return val;
+}
+
+static inline unsigned int mmio_config_readl(void __iomem *pos)
+{
+	u32 val;
+	asm volatile("movl (%1),%%eax" : "=a" (val) : "r" (pos));
+	return val;
+}
+
+static inline void mmio_config_writeb(void __iomem *pos, u8 val)
+{
+	asm volatile("movb %%al,(%1)" :: "a" (val), "r" (pos) : "memory");
+}
+
+static inline void mmio_config_writew(void __iomem *pos, u16 val)
+{
+	asm volatile("movw %%ax,(%1)" :: "a" (val), "r" (pos) : "memory");
+}
+
+static inline void mmio_config_writel(void __iomem *pos, u32 val)
+{
+	asm volatile("movl %%eax,(%1)" :: "a" (val), "r" (pos) : "memory");
+}

arch/x86_64/pci/mmconfig.c

···
 
 	switch (len) {
 	case 1:
-		*value = readb(addr + reg);
+		*value = mmio_config_readb(addr + reg);
 		break;
 	case 2:
-		*value = readw(addr + reg);
+		*value = mmio_config_readw(addr + reg);
 		break;
 	case 4:
-		*value = readl(addr + reg);
+		*value = mmio_config_readl(addr + reg);
 		break;
 	}
 
···
 
 	switch (len) {
 	case 1:
-		writeb(value, addr + reg);
+		mmio_config_writeb(addr + reg, value);
 		break;
 	case 2:
-		writew(value, addr + reg);
+		mmio_config_writew(addr + reg, value);
 		break;
 	case 4:
-		writel(value, addr + reg);
+		mmio_config_writel(addr + reg, value);
 		break;
 	}