linux-kernel - Re: [PATCH 1/2] PCI: ASPM: Allow OS to configure ASPM where BIOS is incapable of

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Message-ID: <db2d9152-7c33-4fbc-8ca5-d70ab9f7598d@canonical.com>
Date: Fri, 26 Jul 2024 15:22:06 +0800
From: Hui Wang <hui.wang@...onical.com>
To: Kai-Heng Feng <kai.heng.feng@...onical.com>, bhelgaas@...gle.com
Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
 nirmal.patel@...ux.intel.com, jonathan.derrick@...ux.dev,
 ilpo.jarvinen@...ux.intel.com, david.e.box@...ux.intel.com,
 AceLan Kao <acelan.kao@...onical.com>
Subject: Re: [PATCH 1/2] PCI: ASPM: Allow OS to configure ASPM where BIOS is
 incapable of

I tested the patchset on a Dell machine (the testing result is positive).

Without the patchset, the ASPM is disabled on the NVME controller:

         LnkCtl:    ASPM Disabled; RCB 64 bytes, Disabled- CommClk+
             ExtSynch- ClockPM- AutWidDis- BWInt- AutBWInt-

After applying the patchset, the ASPM is enabled on the NVME controller:

          LnkCtl:    ASPM L1 Enabled; RCB 64 bytes, Disabled- CommClk+
             ExtSynch- ClockPM+ AutWidDis- BWInt- AutBWInt-


Regards,

Hui.


On 5/30/24 16:52, Kai-Heng Feng wrote:
> Since commit f492edb40b54 ("PCI: vmd: Add quirk to configure PCIe ASPM
> and LTR"), ASPM is configured for NVMe devices enabled in VMD domain.
>
> However, that doesn't cover the case when FADT has ACPI_FADT_NO_ASPM
> set.
>
> So add a new attribute to bypass aspm_disabled so OS can configure ASPM.
>
> Fixes: f492edb40b54 ("PCI: vmd: Add quirk to configure PCIe ASPM and LTR")
> Link: https://lore.kernel.org/linux-pm/218aa81f-9c6-5929-578d-8dc15f83dd48@panix.com/
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> ---
>   drivers/pci/pcie/aspm.c | 8 ++++++--
>   include/linux/pci.h     | 1 +
>   2 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index cee2365e54b8..e719605857b1 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -1416,8 +1416,12 @@ static int __pci_enable_link_state(struct pci_dev *pdev, int state, bool locked)
>   	 * the _OSC method), we can't honor that request.
>   	 */
>   	if (aspm_disabled) {
> -		pci_warn(pdev, "can't override BIOS ASPM; OS doesn't have ASPM control\n");
> -		return -EPERM;
> +		if (aspm_support_enabled && pdev->aspm_os_control)
> +			pci_info(pdev, "BIOS can't program ASPM, let OS control it\n");
> +		else {
> +			pci_warn(pdev, "can't override BIOS ASPM; OS doesn't have ASPM control\n");
> +			return -EPERM;
> +		}
>   	}
>   
>   	if (!locked)
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index fb004fd4e889..58cbd4bea320 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -467,6 +467,7 @@ struct pci_dev {
>   	unsigned int	no_command_memory:1;	/* No PCI_COMMAND_MEMORY */
>   	unsigned int	rom_bar_overlap:1;	/* ROM BAR disable broken */
>   	unsigned int	rom_attr_enabled:1;	/* Display of ROM attribute enabled? */
> +	unsigned int	aspm_os_control:1;	/* Display of ROM attribute enabled? */
>   	pci_dev_flags_t dev_flags;
>   	atomic_t	enable_cnt;	/* pci_enable_device has been called */
>