PCI: Use msleep instead of cpu_relax during ASPM link retraining (987a4c78) · Commits · 戴 / test

The cpu_relax() function can be a noop on certain architectures like IA-64 when CPU threads are disabled, so use msleep instead during link retraining busy/wait loop. Introduce define LINK_RETRAIN_TIMEOUT instead of hard-coding timeout in pcie_aspm_configure_common_clock. Use time_after() to avoid jiffy wraparound when checking for expired timeout. After timeout expires, recheck link status register link training bit instead of checking for expired timeout to avoid possible false positive. Note that Matthew Wilcox came up with the first rough version of this patch. Reviewed-by:

Matthew Wilcox <willy@linux.intel.com> Signed-off-by:

Andrew Patterson <andrew.patterson@hp.com> Signed-off-by:

Jesse Barnes <jbarnes@virtuousgeek.org>

drivers/pci/pcie/aspm.c

+9 −4

Original line number	Diff line number	Diff line
		@@ -17,6 +17,7 @@
		#include <linux/init.h>
		#include <linux/slab.h>
		#include <linux/jiffies.h>
		#include <linux/delay.h>
		#include <linux/pci-aspm.h>
		#include "../pci.h"

		@@ -75,6 +76,8 @@ static const char *policy_str[] = {
		[POLICY_POWERSAVE] = "powersave"
		};

		#define LINK_RETRAIN_TIMEOUT HZ

		static int policy_to_aspm_state(struct pci_dev *pdev)
		{
		struct pcie_link_state *link_state = pdev->link_state;
		@@ -238,16 +241,18 @@ static void pcie_aspm_configure_common_clock(struct pci_dev *pdev)
		pci_write_config_word(pdev, pos + PCI_EXP_LNKCTL, reg16);

		/* Wait for link training end */
		/* break out after waiting for 1 second */
		/* break out after waiting for timeout */
		start_jiffies = jiffies;
		while ((jiffies - start_jiffies) < HZ) {
		for (;;) {
		pci_read_config_word(pdev, pos + PCI_EXP_LNKSTA, &reg16);
		if (!(reg16 & PCI_EXP_LNKSTA_LT))
		break;
		cpu_relax();
		if (time_after(jiffies, start_jiffies + LINK_RETRAIN_TIMEOUT))
		break;
		msleep(1);
		}
		/* training failed -> recover */
		if ((jiffies - start_jiffies) >= HZ) {
		if (reg16 & PCI_EXP_LNKSTA_LT) {
		dev_printk (KERN_ERR, &pdev->dev, "ASPM: Could not configure"
		" common clock\n");
		i = 0;

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