[PATCH] PCI: Software visible configuration request retry status

PCI Express allows cards to return "Configuration Request Retry" if they're
not ready to handle accesses to configuration space.  The PCI Express 1.0a
specification says that the Root Complex should retry the access.  ECN 27
http://www.pcisig.com/specifications/pciexpress/ECN_CRS_Software_Visibility_No27.pdf
allows software to handle the CRS.
Signed-off-by: Matthew Wilcox <matthew@wil.cx>
Signed-off-by: Greg Kroah-Hartman <greg@kroah.com>

drivers/pci/probe.c

@@ -2,6 +2,7 @@
  * probe.c - PCI detection and setup code
  */
 
+#include <linux/delay.h>
 #include <linux/init.h>
 #include <linux/pci.h>
 #include <linux/slab.h>
@@ -336,6 +337,22 @@ struct pci_bus * __devinit pci_add_new_bus(struct pci_bus *parent, struct pci_de
 	return child;
 }
 
+static void pci_enable_crs(struct pci_dev *dev)
+{
+	u16 cap, rpctl;
+	int rpcap = pci_find_capability(dev, PCI_CAP_ID_EXP);
+	if (!rpcap)
+		return;
+
+	pci_read_config_word(dev, rpcap + PCI_CAP_FLAGS, &cap);
+	if (((cap & PCI_EXP_FLAGS_TYPE) >> 4) != PCI_EXP_TYPE_ROOT_PORT)
+		return;
+
+	pci_read_config_word(dev, rpcap + PCI_EXP_RTCTL, &rpctl);
+	rpctl |= PCI_EXP_RTCTL_CRSSVE;
+	pci_write_config_word(dev, rpcap + PCI_EXP_RTCTL, rpctl);
+}
+
 unsigned int __devinit pci_scan_child_bus(struct pci_bus *bus);
 
 /*
@@ -366,6 +383,8 @@ int __devinit pci_scan_bridge(struct pci_bus *bus, struct pci_dev * dev, int max
 	pci_write_config_word(dev, PCI_BRIDGE_CONTROL,
 			      bctl & ~PCI_BRIDGE_CTL_MASTER_ABORT);
 
+	pci_enable_crs(dev);
+
 	if ((buses & 0xffff00) && !pcibios_assign_all_busses() && !is_cardbus) {
 		unsigned int cmax, busnr;
 		/*
@@ -614,9 +633,7 @@ pci_scan_device(struct pci_bus *bus, int devfn)
 	struct pci_dev *dev;
 	u32 l;
 	u8 hdr_type;
-
-	if (pci_bus_read_config_byte(bus, devfn, PCI_HEADER_TYPE, &hdr_type))
-		return NULL;
+	int delay = 1;
 
 	if (pci_bus_read_config_dword(bus, devfn, PCI_VENDOR_ID, &l))
 		return NULL;
@@ -626,6 +643,25 @@ pci_scan_device(struct pci_bus *bus, int devfn)
 	    l == 0x0000ffff || l == 0xffff0000)
 		return NULL;
 
+	/* Configuration request Retry Status */
+	while (l == 0xffff0001) {
+		msleep(delay);
+		delay *= 2;
+		if (pci_bus_read_config_dword(bus, devfn, PCI_VENDOR_ID, &l))
+			return NULL;
+		/* Card hasn't responded in 60 seconds?  Must be stuck. */
+		if (delay > 60 * 1000) {
+			printk(KERN_WARNING "Device %04x:%02x:%02x.%d not "
+					"responding\n", pci_domain_nr(bus),
+					bus->number, PCI_SLOT(devfn),
+					PCI_FUNC(devfn));
+			return NULL;
+		}
+	}
+
+	if (pci_bus_read_config_byte(bus, devfn, PCI_HEADER_TYPE, &hdr_type))
+		return NULL;
+
 	dev = kmalloc(sizeof(struct pci_dev), GFP_KERNEL);
 	if (!dev)
 		return NULL;

include/linux/pci.h

@@ -364,6 +364,20 @@
 #define  PCI_EXP_DEVSTA_URD	0x08	/* Unsupported Request Detected */
 #define  PCI_EXP_DEVSTA_AUXPD	0x10	/* AUX Power Detected */
 #define  PCI_EXP_DEVSTA_TRPND	0x20	/* Transactions Pending */
+#define PCI_EXP_LNKCAP		12	/* Link Capabilities */
+#define PCI_EXP_LNKCTL		16	/* Link Control */
+#define PCI_EXP_LNKSTA		18	/* Link Status */
+#define PCI_EXP_SLTCAP		20	/* Slot Capabilities */
+#define PCI_EXP_SLTCTL		24	/* Slot Control */
+#define PCI_EXP_SLTSTA		26	/* Slot Status */
+#define PCI_EXP_RTCTL		28	/* Root Control */
+#define  PCI_EXP_RTCTL_SECEE	0x01	/* System Error on Correctable Error */
+#define  PCI_EXP_RTCTL_SENFEE	0x02	/* System Error on Non-Fatal Error */
+#define  PCI_EXP_RTCTL_SEFEE	0x04	/* System Error on Fatal Error */
+#define  PCI_EXP_RTCTL_PMEIE	0x08	/* PME Interrupt Enable */
+#define  PCI_EXP_RTCTL_CRSSVE	0x10	/* CRS Software Visibility Enable */
+#define PCI_EXP_RTCAP		30	/* Root Capabilities */
+#define PCI_EXP_RTSTA		32	/* Root Status */
 
 /* Extended Capabilities (PCI-X 2.0 and Express) */
 #define PCI_EXT_CAP_ID(header)		(header & 0x0000ffff)