commit 2a42d9dba7842422ffb2c02e75288a8bc2fd5065
author Thomas Renninger <trenn@suse.de> Tue Dec 09 13:05:09 2008 +0100
committer Jesse Barnes <jbarnes@virtuousgeek.org> Tue Dec 09 14:59:24 2008 -0800
tree d9cfe4822696f60b6cd79683ea53174f7cb74730
parent 3b5dd45e947ecd21491e1658fba7bb4bc4a54995

PCIe: ASPM: Break out of endless loop waiting for PCI config bits to switch

Makes a Compaq 6735s boot reliably again.  It used to hang in the loop
on some boots.  Give the link one second to train, otherwise break out
of the loop and reset the previously set clock bits.

Cc: stable@vger.kernel.org
Signed-off-by: Thomas Renninger <trenn@suse.de>
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Matthew Garrett <mjg59@srcf.ucam.org>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>

drivers/pci/pcie/aspm.c

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 8f63f4c..9aad608 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -16,6 +16,7 @@
 #include <linux/pm.h>
 #include <linux/init.h>
 #include <linux/slab.h>
+#include <linux/jiffies.h>
 #include <linux/pci-aspm.h>
 #include "../pci.h"
 
@@ -161,11 +162,12 @@
  */
 static void pcie_aspm_configure_common_clock(struct pci_dev *pdev)
 {
-	int pos, child_pos;
+	int pos, child_pos, i = 0;
 	u16 reg16 = 0;
 	struct pci_dev *child_dev;
 	int same_clock = 1;
-
+	unsigned long start_jiffies;
+	u16 child_regs[8], parent_reg;
 	/*
 	 * all functions of a slot should have the same Slot Clock
 	 * Configuration, so just check one function
@@ -191,16 +193,19 @@
 		child_pos = pci_find_capability(child_dev, PCI_CAP_ID_EXP);
 		pci_read_config_word(child_dev, child_pos + PCI_EXP_LNKCTL,
 			&reg16);
+		child_regs[i] = reg16;
 		if (same_clock)
 			reg16 |= PCI_EXP_LNKCTL_CCC;
 		else
 			reg16 &= ~PCI_EXP_LNKCTL_CCC;
 		pci_write_config_word(child_dev, child_pos + PCI_EXP_LNKCTL,
 			reg16);
+		i++;
 	}
 
 	/* Configure upstream component */
 	pci_read_config_word(pdev, pos + PCI_EXP_LNKCTL, &reg16);
+	parent_reg = reg16;
 	if (same_clock)
 		reg16 |= PCI_EXP_LNKCTL_CCC;
 	else
@@ -212,12 +217,30 @@
 	pci_write_config_word(pdev, pos + PCI_EXP_LNKCTL, reg16);
 
 	/* Wait for link training end */
-	while (1) {
+	/* break out after waiting for 1 second */
+	start_jiffies = jiffies;
+	while ((jiffies - start_jiffies) < HZ) {
 		pci_read_config_word(pdev, pos + PCI_EXP_LNKSTA, &reg16);
 		if (!(reg16 & PCI_EXP_LNKSTA_LT))
 			break;
 		cpu_relax();
 	}
+	/* training failed -> recover */
+	if ((jiffies - start_jiffies) >= HZ) {
+		dev_printk (KERN_ERR, &pdev->dev, "ASPM: Could not configure"
+			    " common clock\n");
+		i = 0;
+		list_for_each_entry(child_dev, &pdev->subordinate->devices,
+				    bus_list) {
+			child_pos = pci_find_capability(child_dev,
+							PCI_CAP_ID_EXP);
+			pci_write_config_word(child_dev,
+					      child_pos + PCI_EXP_LNKCTL,
+					      child_regs[i]);
+			i++;
+		}
+		pci_write_config_word(pdev, pos + PCI_EXP_LNKCTL, parent_reg);
+	}
 }
 
 /*