linux-kernel - [PATCH] pci: completely disable aspm if it's unsupported

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Message-ID: <1447856703-2566-1-git-send-email-jbacik@fb.com>
Date:	Wed, 18 Nov 2015 09:25:03 -0500
From:	Josef Bacik <jbacik@...com>
To:	<linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-acpi@...r.kernel.org>, <bhelgaas@...gle.com>, <shli@...com>,
	<kernel-team@...com>
Subject: [PATCH] pci: completely disable aspm if it's unsupported

We have some hardware that takes about 30 seconds to setup common clocks for
ASPM, but our bios'es don't actually allow ASPM.  It seems we had this thing in
place where we would disable ASPM after the pci bus probe so that we would make
sure that pre pcie 1.1 devices would be properly skipped during initialization.
This is because the mechanism to disable ASPM doesn't actually disable the
setting up of the link state stuff, it just keeps us from changing the link
state after the fact.  So instead make it so that when we call pcie_no_aspm()
that we disable ASPM completley, that is we skip setting up the link state and
everything.  This way we avoid the costly setup for a feature we cannot support
in the first place and we also make sure we are safe from future tampering with
the ASPM link state.  Thanks,

Signed-off-by: Josef Bacik <jbacik@...com>
---
 drivers/acpi/pci_root.c | 22 +++++-----------------
 drivers/pci/pcie/aspm.c |  1 +
 2 files changed, 6 insertions(+), 17 deletions(-)

diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index 393706a..00e164a 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -419,7 +419,7 @@ out:
 }
 EXPORT_SYMBOL(acpi_pci_osc_control_set);
 
-static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm)
+static void negotiate_os_control(struct acpi_pci_root *root)
 {
 	u32 support, control, requested;
 	acpi_status status;
@@ -456,7 +456,7 @@ static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm)
 	if (ACPI_FAILURE(status)) {
 		dev_info(&device->dev, "_OSC failed (%s); disabling ASPM\n",
 			 acpi_format_exception(status));
-		*no_aspm = 1;
+		pcie_no_aspm();
 		return;
 	}
 
@@ -495,22 +495,14 @@ static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm)
 			 * intact and prevent the OS from touching it.
 			 */
 			dev_info(&device->dev, "FADT indicates ASPM is unsupported, using BIOS configuration\n");
-			*no_aspm = 1;
+			pcie_no_aspm();
 		}
 	} else {
 		decode_osc_control(root, "OS requested", requested);
 		decode_osc_control(root, "platform willing to grant", control);
 		dev_info(&device->dev, "_OSC failed (%s); disabling ASPM\n",
 			acpi_format_exception(status));
-
-		/*
-		 * We want to disable ASPM here, but aspm_disabled
-		 * needs to remain in its state from boot so that we
-		 * properly handle PCIe 1.1 devices.  So we set this
-		 * flag here, to defer the action until after the ACPI
-		 * root scan.
-		 */
-		*no_aspm = 1;
+		pcie_no_aspm();
 	}
 }
 
@@ -522,7 +514,6 @@ static int acpi_pci_root_add(struct acpi_device *device,
 	int result;
 	struct acpi_pci_root *root;
 	acpi_handle handle = device->handle;
-	int no_aspm = 0;
 	bool hotadd = system_state != SYSTEM_BOOTING;
 
 	root = kzalloc(sizeof(struct acpi_pci_root), GFP_KERNEL);
@@ -581,7 +572,7 @@ static int acpi_pci_root_add(struct acpi_device *device,
 
 	root->mcfg_addr = acpi_pci_root_get_mcfg_addr(handle);
 
-	negotiate_os_control(root, &no_aspm);
+	negotiate_os_control(root);
 
 	/*
 	 * TBD: Need PCI interface for enumeration/configuration of roots.
@@ -604,9 +595,6 @@ static int acpi_pci_root_add(struct acpi_device *device,
 		goto remove_dmar;
 	}
 
-	if (no_aspm)
-		pcie_no_aspm();
-
 	pci_acpi_add_bus_pm_notifier(device);
 	if (device->wakeup.flags.run_wake)
 		device_set_run_wake(root->bus->bridge, true);
diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 317e355..5f84af2 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -954,6 +954,7 @@ void pcie_no_aspm(void)
 	if (!aspm_force) {
 		aspm_policy = POLICY_DEFAULT;
 		aspm_disabled = 1;
+		aspm_support_enabled = false;
 	}
 }
 
-- 
2.1.0

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