PCI x86: always use conf1 to access config space below 256 bytes

Thanks to Loic Prylli <loic@myri.com>, who originally proposed
this idea.

Always using legacy configuration mechanism for the legacy config space
and extended mechanism (mmconf) for the extended config space is
a simple and very logical approach. It's supposed to resolve all
known mmconf problems. It still allows per-device quirks (tweaking
dev->cfg_size). It also allows to get rid of mmconf fallback code.

Signed-off-by: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Signed-off-by: Matthew Wilcox <willy@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/x86/pci/mmconfig-shared.c

@@ -22,42 +22,9 @@
 #define MMCONFIG_APER_MIN	(2 * 1024*1024)
 #define MMCONFIG_APER_MAX	(256 * 1024*1024)
 
-DECLARE_BITMAP(pci_mmcfg_fallback_slots, 32*PCI_MMCFG_MAX_CHECK_BUS);
-
 /* Indicate if the mmcfg resources have been placed into the resource table. */
 static int __initdata pci_mmcfg_resources_inserted;
 
-/* K8 systems have some devices (typically in the builtin northbridge)
-   that are only accessible using type1
-   Normally this can be expressed in the MCFG by not listing them
-   and assigning suitable _SEGs, but this isn't implemented in some BIOS.
-   Instead try to discover all devices on bus 0 that are unreachable using MM
-   and fallback for them. */
-static void __init unreachable_devices(void)
-{
-	int i, bus;
-	/* Use the max bus number from ACPI here? */
-	for (bus = 0; bus < PCI_MMCFG_MAX_CHECK_BUS; bus++) {
-		for (i = 0; i < 32; i++) {
-			unsigned int devfn = PCI_DEVFN(i, 0);
-			u32 val1, val2;
-
-			pci_conf1_read(0, bus, devfn, 0, 4, &val1);
-			if (val1 == 0xffffffff)
-				continue;
-
-			if (pci_mmcfg_arch_reachable(0, bus, devfn)) {
-				raw_pci_ops->read(0, bus, devfn, 0, 4, &val2);
-				if (val1 == val2)
-					continue;
-			}
-			set_bit(i + 32 * bus, pci_mmcfg_fallback_slots);
-			printk(KERN_NOTICE "PCI: No mmconfig possible on device"
-			       " %02x:%02x\n", bus, i);
-		}
-	}
-}
-
 static const char __init *pci_mmcfg_e7520(void)
 {
 	u32 win;
@@ -270,8 +237,6 @@ void __init pci_mmcfg_init(int type)
 		return;
 
 	if (pci_mmcfg_arch_init()) {
-		if (type == 1)
-			unreachable_devices();
 		if (known_bridge)
 			pci_mmcfg_insert_resources(IORESOURCE_BUSY);
 		pci_probe = (pci_probe & ~PCI_PROBE_MASK) | PCI_PROBE_MMCONF;

arch/x86/pci/mmconfig_32.c

@@ -30,10 +30,6 @@ static u32 get_base_addr(unsigned int seg, int bus, unsigned devfn)
 	struct acpi_mcfg_allocation *cfg;
 	int cfg_num;
 
-	if (seg == 0 && bus < PCI_MMCFG_MAX_CHECK_BUS &&
-	    test_bit(PCI_SLOT(devfn) + 32*bus, pci_mmcfg_fallback_slots))
-		return 0;
-
 	for (cfg_num = 0; cfg_num < pci_mmcfg_config_num; cfg_num++) {
 		cfg = &pci_mmcfg_config[cfg_num];
 		if (cfg->pci_segment == seg &&
@@ -68,13 +64,16 @@ static int pci_mmcfg_read(unsigned int seg, unsigned int bus,
 	u32 base;
 
 	if ((bus > 255) || (devfn > 255) || (reg > 4095)) {
-		*value = -1;
+err:		*value = -1;
 		return -EINVAL;
 	}
 
+	if (reg < 256)
+		return pci_conf1_read(seg,bus,devfn,reg,len,value);
+
 	base = get_base_addr(seg, bus, devfn);
 	if (!base)
-		return pci_conf1_read(seg,bus,devfn,reg,len,value);
+		goto err;
 
 	spin_lock_irqsave(&pci_config_lock, flags);
 
@@ -105,9 +104,12 @@ static int pci_mmcfg_write(unsigned int seg, unsigned int bus,
 	if ((bus > 255) || (devfn > 255) || (reg > 4095))
 		return -EINVAL;
 
+	if (reg < 256)
+		return pci_conf1_write(seg,bus,devfn,reg,len,value);
+
 	base = get_base_addr(seg, bus, devfn);
 	if (!base)
-		return pci_conf1_write(seg,bus,devfn,reg,len,value);
+		return -EINVAL;
 
 	spin_lock_irqsave(&pci_config_lock, flags);
 
@@ -134,12 +136,6 @@ static struct pci_raw_ops pci_mmcfg = {
 	.write =	pci_mmcfg_write,
 };
 
-int __init pci_mmcfg_arch_reachable(unsigned int seg, unsigned int bus,
-				    unsigned int devfn)
-{
-	return get_base_addr(seg, bus, devfn) != 0;
-}
-
 int __init pci_mmcfg_arch_init(void)
 {
 	printk(KERN_INFO "PCI: Using MMCONFIG\n");

arch/x86/pci/mmconfig_64.c

@@ -40,9 +40,7 @@ static char __iomem *get_virt(unsigned int seg, unsigned bus)
 static char __iomem *pci_dev_base(unsigned int seg, unsigned int bus, unsigned int devfn)
 {
 	char __iomem *addr;
-	if (seg == 0 && bus < PCI_MMCFG_MAX_CHECK_BUS &&
-		test_bit(32*bus + PCI_SLOT(devfn), pci_mmcfg_fallback_slots))
-		return NULL;
+
 	addr = get_virt(seg, bus);
 	if (!addr)
 		return NULL;
@@ -56,13 +54,16 @@ static int pci_mmcfg_read(unsigned int seg, unsigned int bus,
 
 	/* Why do we have this when nobody checks it. How about a BUG()!? -AK */
 	if (unlikely((bus > 255) || (devfn > 255) || (reg > 4095))) {
-		*value = -1;
+err:		*value = -1;
 		return -EINVAL;
 	}
 
+	if (reg < 256)
+		return pci_conf1_read(seg,bus,devfn,reg,len,value);
+
 	addr = pci_dev_base(seg, bus, devfn);
 	if (!addr)
-		return pci_conf1_read(seg,bus,devfn,reg,len,value);
+		goto err;
 
 	switch (len) {
 	case 1:
@@ -88,9 +89,12 @@ static int pci_mmcfg_write(unsigned int seg, unsigned int bus,
 	if (unlikely((bus > 255) || (devfn > 255) || (reg > 4095)))
 		return -EINVAL;
 
+	if (reg < 256)
+		return pci_conf1_write(seg,bus,devfn,reg,len,value);
+
 	addr = pci_dev_base(seg, bus, devfn);
 	if (!addr)
-		return pci_conf1_write(seg,bus,devfn,reg,len,value);
+		return -EINVAL;
 
 	switch (len) {
 	case 1:
@@ -126,12 +130,6 @@ static void __iomem * __init mcfg_ioremap(struct acpi_mcfg_allocation *cfg)
 	return addr;
 }
 
-int __init pci_mmcfg_arch_reachable(unsigned int seg, unsigned int bus,
-				    unsigned int devfn)
-{
-	return pci_dev_base(seg, bus, devfn) != NULL;
-}
-
 int __init pci_mmcfg_arch_init(void)
 {
 	int i;

arch/x86/pci/pci.h

@@ -98,13 +98,6 @@ extern void pcibios_sort(void);
 
 /* pci-mmconfig.c */
 
-/* Verify the first 16 busses. We assume that systems with more busses
-   get MCFG right. */
-#define PCI_MMCFG_MAX_CHECK_BUS 16
-extern DECLARE_BITMAP(pci_mmcfg_fallback_slots, 32*PCI_MMCFG_MAX_CHECK_BUS);
-
-extern int __init pci_mmcfg_arch_reachable(unsigned int seg, unsigned int bus,
-					   unsigned int devfn);
 extern int __init pci_mmcfg_arch_init(void);
 
 /*