linux-kernel - Re: [PATCH] PCI/ASPM: Enable ASPM for links under VMD domain

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Date:   Mon, 24 Aug 2020 16:04:56 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>
Cc:     bhelgaas@...gle.com, jonathan.derrick@...el.com,
        Mario.Limonciello@...l.com, Heiner Kallweit <hkallweit1@...il.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Xiongfeng Wang <wangxiongfeng2@...wei.com>,
        Krzysztof Wilczynski <kw@...ux.com>,
        "open list:PCI SUBSYSTEM" <linux-pci@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] PCI/ASPM: Enable ASPM for links under VMD domain

Hi,

On Fri, Aug 21, 2020 at 08:32:20PM +0800, Kai-Heng Feng wrote:
> New Intel laptops with VMD cannot reach deeper power saving state,
> renders very short battery time.
> 
> As BIOS may not be able to program the config space for devices under
> VMD domain, ASPM needs to be programmed manually by software. This is
> also the case under Windows.
> 
> The VMD controller itself is a root complex integrated endpoint that
> doesn't have ASPM capability, so we can't propagate the ASPM settings to
> devices under it. Hence, simply apply ASPM_STATE_ALL to the links under
> VMD domain, unsupported states will be cleared out anyway.
> 
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> ---
>  drivers/pci/pcie/aspm.c |  3 ++-
>  drivers/pci/quirks.c    | 11 +++++++++++
>  include/linux/pci.h     |  2 ++
>  3 files changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index 253c30cc1967..dcc002dbca19 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -624,7 +624,8 @@ static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
>  		aspm_calc_l1ss_info(link, &upreg, &dwreg);
>  
>  	/* Save default state */
> -	link->aspm_default = link->aspm_enabled;
> +	link->aspm_default = parent->dev_flags & PCI_DEV_FLAGS_ENABLE_ASPM ?
> +			     ASPM_STATE_ALL : link->aspm_enabled;
>  
>  	/* Setup initial capable state. Will be updated later */
>  	link->aspm_capable = link->aspm_support;
> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
> index bdf9b52567e0..2e2f525bd892 100644
> --- a/drivers/pci/quirks.c
> +++ b/drivers/pci/quirks.c
> @@ -5632,3 +5632,14 @@ static void apex_pci_fixup_class(struct pci_dev *pdev)
>  }
>  DECLARE_PCI_FIXUP_CLASS_HEADER(0x1ac1, 0x089a,
>  			       PCI_CLASS_NOT_DEFINED, 8, apex_pci_fixup_class);
> +
> +/*
> + * Device [8086:9a09]
> + * BIOS may not be able to access config space of devices under VMD domain, so
> + * it relies on software to enable ASPM for links under VMD.
> + */
> +static void pci_fixup_enable_aspm(struct pci_dev *pdev)
> +{
> +	pdev->dev_flags |= PCI_DEV_FLAGS_ENABLE_ASPM;
> +}
> +DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x9a09, pci_fixup_enable_aspm);
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 835530605c0d..66a45916c7c6 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -227,6 +227,8 @@ enum pci_dev_flags {
>  	PCI_DEV_FLAGS_NO_FLR_RESET = (__force pci_dev_flags_t) (1 << 10),
>  	/* Don't use Relaxed Ordering for TLPs directed at this device */
>  	PCI_DEV_FLAGS_NO_RELAXED_ORDERING = (__force pci_dev_flags_t) (1 << 11),
> +	/* Enable ASPM regardless of how LnkCtl is programmed */
> +	PCI_DEV_FLAGS_ENABLE_ASPM = (__force pci_dev_flags_t) (1 << 12),

I wonder if instead of dev_flags this should have a bit field in struct
pci_dev? Not sure which one is prefered actually, both seem to include
quirks as well ;-)

>  };
>  
>  enum pci_irq_reroute_variant {
> -- 
> 2.17.1