linux-kernel - Re: [PATCH v2] PCI: Disable ASPM if BIOS asks us to

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Date:	Mon, 6 Dec 2010 23:20:36 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Matthew Garrett <mjg@...hat.com>
Cc:	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	jbarnes@...tuousgeek.org
Subject: Re: [PATCH v2] PCI: Disable ASPM if BIOS asks us to

On Monday, December 06, 2010, Matthew Garrett wrote:
> We currently refuse to touch the ASPM registers if the BIOS tells us that
> ASPM isn't supported. This can cause problems if the BIOS has (for any
> reason) enabled ASPM on some devices anyway. Change the code such that we
> explicitly clear ASPM if the FADT indicates that ASPM isn't supported,
> and make sure we tidy up appropriately on device removal in order to deal
> with the hotplug case. If ASPM is disabled because the BIOS doesn't hand
> over control then we won't touch the registers.
> 
> Signed-off-by: Matthew Garrett <mjg@...hat.com>

Acked-by: Rafael J. Wysocki <rjw@...k.pl>

> ---
> 
> Implement Rafael's suggestion to use two separate functions, and also
> ensure that we clear the clkpm bit as well as the ASPM bits.
> 
>  drivers/pci/pci-acpi.c   |    1 +
>  drivers/pci/pcie/aspm.c  |   21 +++++++++++++++++----
>  include/linux/pci-aspm.h |    5 ++++-
>  3 files changed, 22 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
> index 24e19c5..d7ea699 100644
> --- a/drivers/pci/pci-acpi.c
> +++ b/drivers/pci/pci-acpi.c
> @@ -399,6 +399,7 @@ static int __init acpi_pci_init(void)
>  
>  	if (acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_ASPM) {
>  		printk(KERN_INFO"ACPI FADT declares the system doesn't support PCIe ASPM, so disable it\n");
> +		pcie_clear_aspm();
>  		pcie_no_aspm();
>  	}
>  
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index 7122281..8112415 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -68,7 +68,7 @@ struct pcie_link_state {
>  	struct aspm_latency acceptable[8];
>  };
>  
> -static int aspm_disabled, aspm_force;
> +static int aspm_disabled, aspm_force, aspm_clear_state;
>  static DEFINE_MUTEX(aspm_lock);
>  static LIST_HEAD(link_list);
>  
> @@ -139,7 +139,7 @@ static void pcie_set_clkpm(struct pcie_link_state *link, int enable)
>  {
>  	/* Don't enable Clock PM if the link is not Clock PM capable */
>  	if (!link->clkpm_capable && enable)
> -		return;
> +		enable = 0;
>  	/* Need nothing if the specified equals to current state */
>  	if (link->clkpm_enabled == enable)
>  		return;
> @@ -498,6 +498,10 @@ static int pcie_aspm_sanity_check(struct pci_dev *pdev)
>  	struct pci_dev *child;
>  	int pos;
>  	u32 reg32;
> +
> +	if (aspm_clear_state)
> +		return -EINVAL;
> +
>  	/*
>  	 * Some functions in a slot might not all be PCIe functions,
>  	 * very strange. Disable ASPM for the whole slot
> @@ -563,12 +567,15 @@ void pcie_aspm_init_link_state(struct pci_dev *pdev)
>  	struct pcie_link_state *link;
>  	int blacklist = !!pcie_aspm_sanity_check(pdev);
>  
> -	if (aspm_disabled || !pci_is_pcie(pdev) || pdev->link_state)
> +	if (!pci_is_pcie(pdev) || pdev->link_state)
>  		return;
>  	if (pdev->pcie_type != PCI_EXP_TYPE_ROOT_PORT &&
>  	    pdev->pcie_type != PCI_EXP_TYPE_DOWNSTREAM)
>  		return;
>  
> +	if (aspm_disabled && !aspm_clear_state)
> +		return;
> +
>  	/* VIA has a strange chipset, root port is under a bridge */
>  	if (pdev->pcie_type == PCI_EXP_TYPE_ROOT_PORT &&
>  	    pdev->bus->self)
> @@ -641,7 +648,7 @@ void pcie_aspm_exit_link_state(struct pci_dev *pdev)
>  	struct pci_dev *parent = pdev->bus->self;
>  	struct pcie_link_state *link, *root, *parent_link;
>  
> -	if (aspm_disabled || !pci_is_pcie(pdev) ||
> +	if ((aspm_disabled && !aspm_clear_state) || !pci_is_pcie(pdev) ||
>  	    !parent || !parent->link_state)
>  		return;
>  	if ((parent->pcie_type != PCI_EXP_TYPE_ROOT_PORT) &&
> @@ -899,6 +906,12 @@ static int __init pcie_aspm_disable(char *str)
>  
>  __setup("pcie_aspm=", pcie_aspm_disable);
>  
> +void pci_clear_aspm(void)
> +{
> +	if (!aspm_force)
> +		aspm_clear_state = 1;
> +}
> +
>  void pcie_no_aspm(void)
>  {
>  	if (!aspm_force)
> diff --git a/include/linux/pci-aspm.h b/include/linux/pci-aspm.h
> index 91ba0b3..ce68105 100644
> --- a/include/linux/pci-aspm.h
> +++ b/include/linux/pci-aspm.h
> @@ -27,6 +27,7 @@ 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 pci_disable_link_state(struct pci_dev *pdev, int state);
> +extern void pcie_clear_aspm(void);
>  extern void pcie_no_aspm(void);
>  #else
>  static inline void pcie_aspm_init_link_state(struct pci_dev *pdev)
> @@ -41,7 +42,9 @@ static inline void pcie_aspm_pm_state_change(struct pci_dev *pdev)
>  static inline void pci_disable_link_state(struct pci_dev *pdev, int state)
>  {
>  }
> -
> +static inline void pcie_clear_aspm(void)
> +{
> +}
>  static inline void pcie_no_aspm(void)
>  {
>  }
> 

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