linux-kernel - Re: [PATCH v5 3/4] PCI/ASPM: Introduce aspm_get_l1ss

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Date: Fri, 26 Apr 2024 16:57:54 -0700
From: "David E. Box" <david.e.box@...ux.intel.com>
To: Jian-Hong Pan <jhp@...lessos.org>, Bjorn Helgaas <helgaas@...nel.org>
Cc: Johan Hovold <johan@...nel.org>, Ilpo Järvinen
 <ilpo.jarvinen@...ux.intel.com>, Kuppuswamy Sathyanarayanan
 <sathyanarayanan.kuppuswamy@...ux.intel.com>, Mika Westerberg
 <mika.westerberg@...ux.intel.com>, Damien Le Moal <dlemoal@...nel.org>, 
 Nirmal Patel <nirmal.patel@...ux.intel.com>, Jonathan Derrick
 <jonathan.derrick@...ux.dev>,  linux-pci@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 3/4] PCI/ASPM: Introduce aspm_get_l1ss_cap()

On Wed, 2024-04-24 at 19:00 +0800, Jian-Hong Pan wrote:
> Introduce aspm_get_l1ss_cap() which is extracted from aspm_l1ss_init() to
> get the PCIe's L1SS capability. This does not change any behavior, but
> aspm_get_l1ss_cap() can be reused later.
> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=218394
> Signed-off-by: Jian-Hong Pan <jhp@...lessos.org>
> ---
>  drivers/pci/pcie/aspm.c | 23 ++++++++++++++---------
>  1 file changed, 14 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index 91a8b35b1ae2..c55ac11faa73 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -612,6 +612,18 @@ static void pcie_aspm_check_latency(struct pci_dev
> *endpoint)
>         }
>  }
>  
> +static u32 aspm_get_l1ss_cap(struct pci_dev *pdev)
> +{
> +       u32 l1ss_cap;
> +
> +       pci_read_config_dword(pdev, pdev->l1ss + PCI_L1SS_CAP, &l1ss_cap);
> +
> +       if (!(l1ss_cap & PCI_L1SS_CAP_L1_PM_SS))
> +               l1ss_cap = 0;
> +
> +       return l1ss_cap;
> +}
> +
>  /* Calculate L1.2 PM substate timing parameters */
>  static void aspm_calc_l12_info(struct pcie_link_state *link,
>                                 u32 parent_l1ss_cap, u32 child_l1ss_cap)
> @@ -722,15 +734,8 @@ static void aspm_l1ss_init(struct pcie_link_state *link)
>                 return;
>  
>         /* Setup L1 substate */
> -       pci_read_config_dword(parent, parent->l1ss + PCI_L1SS_CAP,
> -                             &parent_l1ss_cap);
> -       pci_read_config_dword(child, child->l1ss + PCI_L1SS_CAP,
> -                             &child_l1ss_cap);
> -
> -       if (!(parent_l1ss_cap & PCI_L1SS_CAP_L1_PM_SS))
> -               parent_l1ss_cap = 0;
> -       if (!(child_l1ss_cap & PCI_L1SS_CAP_L1_PM_SS))
> -               child_l1ss_cap = 0;
> +       parent_l1ss_cap = aspm_get_l1ss_cap(parent);
> +       child_l1ss_cap = aspm_get_l1ss_cap(child);
>  
>         /*
>          * If we don't have LTR for the entire path from the Root Complex

Reviewed-by: David E. Box <david.e.box@...ux.intel.com>