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

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Date:	Thu, 3 Dec 2015 23:40:13 +0100
From:	Pavel Machek <pavel@....cz>
To:	Josef Bacik <jbacik@...com>
Cc:	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org, bhelgaas@...gle.com, shli@...com,
	kernel-team@...com
Subject: Re: [PATCH] pci: completely disable aspm if it's unsupported

Hi!

> 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,

On thinkpad x60, I have similar problem.

I'm carying this for long long time now:

diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
index a32ba75..5eb7621 100644
--- a/drivers/pci/pci-acpi.c
+++ b/drivers/pci/pci-acpi.c
@@ -700,7 +700,7 @@ static int __init acpi_pci_init(void)
 
 	if (acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_ASPM) {
 		pr_info("ACPI FADT declares the system doesn't support PCIe ASPM, so disable it\n");
-		pcie_no_aspm();
+//		pcie_no_aspm();
 	}
 
 	ret = register_acpi_bus_type(&acpi_pci_bus);



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