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Message-ID: <3da4a67c-75e7-5100-dd8b-eee6a442a8c8@intel.com>
Date:   Thu, 19 Jan 2023 20:01:37 +0100
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Subject: Re: [PATCH V1] PCI/ASPM: Skip L1SS save/restore if not already
 enabled
To:     Kai-Heng Feng <kai.heng.feng@canonical.com>,
        Vidya Sagar <vidyas@nvidia.com>
CC:     <bhelgaas@google.com>,
        <sathyanarayanan.kuppuswamy@linux.intel.com>,
        <enriquezmark36@gmail.com>, <tasev.stefanoska@skynet.be>,
        <linux-pci@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <treding@nvidia.com>, <jonathanh@nvidia.com>, <kthota@nvidia.com>,
        <mmaddireddy@nvidia.com>, <sagar.tv@gmail.com>
References: <20230119094913.20536-1-vidyas@nvidia.com>
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On 1/19/2023 3:21 PM, Kai-Heng Feng wrote:
> Hi Vidya,
>
> On Thu, Jan 19, 2023 at 5:49 PM Vidya Sagar <vidyas@nvidia.com> wrote:
>> Skip save and restore of ASPM L1 Sub-States specific registers if they
>> are not already enabled in the system. This is to avoid issues observed
>> on certain platforms during restoration process, particularly when
>> restoring the L1SS registers contents.
>>
>> BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=216782
>> Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
>> ---
>>   drivers/pci/pcie/aspm.c | 19 ++++++++++++++++++-
>>   1 file changed, 18 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
>> index 53a1fa306e1e..5d3f09b0a6a9 100644
>> --- a/drivers/pci/pcie/aspm.c
>> +++ b/drivers/pci/pcie/aspm.c
>> @@ -757,15 +757,29 @@ static void pcie_config_aspm_l1ss(struct pcie_link_state *link, u32 state)
>>                                  PCI_L1SS_CTL1_L1SS_MASK, val);
>>   }
>>
>> +static bool skip_l1ss_restore;
> Maybe move it inside "struct pci_dev"?

Yes, it can be different for different devices, so it cannot be static IMV.


>> +
>>   void pci_save_aspm_l1ss_state(struct pci_dev *dev)
>>   {
>>          struct pci_cap_saved_state *save_state;
>>          u16 l1ss = dev->l1ss;
>> -       u32 *cap;
>> +       u32 *cap, val;
>>
>>          if (!l1ss)
>>                  return;
>>
>> +       /*
>> +        * Skip save and restore of L1 Sub-States registers if they are not
>> +        * already enabled in the system
>> +        */
>> +       pci_read_config_dword(dev, l1ss + PCI_L1SS_CTL1, &val);
>> +       if (!(val & PCI_L1SS_CTL1_L1SS_MASK)) {
>> +               skip_l1ss_restore = 1;
>> +               return;
>> +       }
>> +
>> +       skip_l1ss_restore = 0;
>> +
>>          save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_L1SS);
>>          if (!save_state)
>>                  return;
>> @@ -784,6 +798,9 @@ void pci_restore_aspm_l1ss_state(struct pci_dev *dev)
>>          if (!l1ss)
>>                  return;
>>
>> +       if (skip_l1ss_restore)
>> +               return;
>> +
>>          save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_L1SS);
>>          if (!save_state)
>>                  return;
>> --
>> 2.17.1
>>