lkml.org 
[lkml]   [2011]   [Mar]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[RFC][PATCH v2]: PCI: PCIe links may not get configured for ASPM under POWERSAVE mode
Date
v2 -> v1:
. Kept the logic in pci_raw_set_power_state
. Changed the ASPM enabling logic
. Modified the text that describes the problem

v1 : http://marc.info/?l=linux-pci&m=130013164703283&w=2

The assumption made in commit 41cd766b065970ff6f6c89dd1cf55fa706c84a3d
(PCI: Don't enable aspm before drivers have had a chance to veto it) that
pci_enable_device() will result in re-configuring ASPM when aspm_policy is
POWERSAVE is no longer valid. This is due to commit
97c145f7c87453cec90e91238fba5fe2c1561b32 (PCI: read current power state
at enable time) which resets dev->current_state to D0. This makes the
equality check (below) become true, so pcie_aspm_pm_state_change() never
gets called.
./drivers/pci/pci.c: pci_raw_set_pci_power_state()
546 /* Check if we're already there */
547 if (dev->current_state == state)
548 return 0;

So OSPM doesnn't configure the PCIe links for ASPM.

The patch below does the following:
At the end of each Root Bridge scan make a call to configure ASPM when the
ASPM policy is set to "powersave" mode. Note that if a previous pass had
completed the configuration for all devices under that Bridge then the
configuration will not take place again because pcie_config_aspm_link()
checks to see if the link is already in the requested state.
We won't reconfigure ASPM when _OSC control is not granted. In fact, we will
disable ASPM in that situation. This is to protect systems with a buggy BIOS
that did not set the FADT bit even though the underlying HW can't do ASPM.

To turn "on" ASPM the minimum the BIOS needs to do:
1. Clear the ACPI FADT "ASPM Controls" bit.
2. Support _OSC appropriately

Signed-off-by: Naga Chumbalkar <nagananda.chumbalkar@hp.com>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Matthew Garrett <mjg59@srcf.ucam.org>

diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index 8524939..c0655aa 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -32,6 +32,7 @@
#include <linux/pm_runtime.h>
#include <linux/pci.h>
#include <linux/pci-acpi.h>
+#include <linux/pci-aspm.h>
#include <linux/acpi.h>
#include <linux/slab.h>
#include <acpi/acpi_bus.h>
@@ -591,12 +592,22 @@ static int __devinit acpi_pci_root_add(struct acpi_device *device)

status = acpi_pci_osc_control_set(device->handle, &flags,
OSC_PCI_EXPRESS_CAP_STRUCTURE_CONTROL);
- if (ACPI_SUCCESS(status))
+
+ if (ACPI_SUCCESS(status)) {
dev_info(root->bus->bridge,
"ACPI _OSC control (0x%02x) granted\n", flags);
- else
+ /*
+ * When aspm_policy is POWERSAVE, this
+ * call ensures that ASPM is configured.
+ */
+ pcie_aspm_reconfig_link(root->bus->self);
+ } else {
dev_dbg(root->bus->bridge,
"ACPI _OSC request failed (code %d)\n", status);
+ printk(KERN_INFO "Unable to assume _OSC PCIe control."
+ " Disabling ASPM.\n");
+ pcie_no_aspm();
+ }
}

pci_acpi_add_bus_pm_notifier(device, root->bus);
diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 3188cd9..1316745 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -742,6 +742,29 @@ void pci_disable_link_state(struct pci_dev *pdev, int state)
}
EXPORT_SYMBOL(pci_disable_link_state);

+void pcie_aspm_reconfig_link(struct pci_dev *pdev)
+{
+ struct pcie_link_state *link = NULL;
+
+ if (aspm_disabled)
+ return;
+ if (aspm_policy != POLICY_POWERSAVE)
+ return;
+
+ down_read(&pci_bus_sem);
+ mutex_lock(&aspm_lock);
+
+ if (list_empty(&link_list))
+ goto out;
+ list_for_each_entry(link, &link_list, sibling) {
+ pcie_config_aspm_link(link, policy_to_aspm_state(link));
+ pcie_set_clkpm(link, policy_to_clkpm_state(link));
+ }
+out:
+ mutex_unlock(&aspm_lock);
+ up_read(&pci_bus_sem);
+}
+
static int pcie_aspm_set_policy(const char *val, struct kernel_param *kp)
{
int i;
diff --git a/drivers/pci/pcie/portdrv_core.c b/drivers/pci/pcie/portdrv_core.c
index 5130d0d..595654a 100644
--- a/drivers/pci/pcie/portdrv_core.c
+++ b/drivers/pci/pcie/portdrv_core.c
@@ -15,7 +15,6 @@
#include <linux/slab.h>
#include <linux/pcieport_if.h>
#include <linux/aer.h>
-#include <linux/pci-aspm.h>

#include "../pci.h"
#include "portdrv.h"
@@ -356,10 +355,8 @@ int pcie_port_device_register(struct pci_dev *dev)

/* Get and check PCI Express port services */
capabilities = get_port_device_capability(dev);
- if (!capabilities) {
- pcie_no_aspm();
+ if (!capabilities)
return 0;
- }

pci_set_master(dev);
/*
diff --git a/include/linux/pci-aspm.h b/include/linux/pci-aspm.h
index ce68105..216b196 100644
--- a/include/linux/pci-aspm.h
+++ b/include/linux/pci-aspm.h
@@ -26,6 +26,7 @@
extern void pcie_aspm_init_link_state(struct pci_dev *pdev);
extern void pcie_aspm_exit_link_state(struct pci_dev *pdev);
extern void pcie_aspm_pm_state_change(struct pci_dev *pdev);
+extern void pcie_aspm_reconfig_link(struct pci_dev *pdev);
extern void pci_disable_link_state(struct pci_dev *pdev, int state);
extern void pcie_clear_aspm(void);
extern void pcie_no_aspm(void);
@@ -39,6 +40,9 @@ static inline void pcie_aspm_exit_link_state(struct pci_dev *pdev)
static inline void pcie_aspm_pm_state_change(struct pci_dev *pdev)
{
}
+static inline void pcie_aspm_reconfig_link(struct pci_dev *pdev)
+{
+}
static inline void pci_disable_link_state(struct pci_dev *pdev, int state)
{
}

\
 
 \ /
  Last update: 2011-03-18 05:25    [W:0.044 / U:2.420 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site