On 3/5/24 2:03 PM, Bjorn Helgaas wrote:
> [+to Sathy, David in case you want to update your Reviewed-by]
>
> On Thu, Feb 22, 2024 at 11:14:36PM +0530, Vidya Sagar wrote:
>> Many PCIe device drivers save the configuration state of their respective
>> devices during probe and restore the same when their 'slot_reset' hook
>> is called through PCIe Error Recovery Handler.
>>
>> If the system has a change in ASPM policy after the driver's probe is
>> called and before error event occurred, 'slot_reset' hook restores the
>> PCIe configuration state to what it was at the time of probe but not to
>> what it was just before the occurrence of the error event.
>> This effectively leads to a mismatch in the ASPM configuration between
>> the device and its upstream parent device.
>>
>> Update the saved configuration state of the device with the latest info
>> whenever there is a change w.r.t ASPM policy.
>>
>> Signed-off-by: Vidya Sagar <vidyas@xxxxxxxxxx>
>> -void pci_save_aspm_state(struct pci_dev *pdev);
>> +void pci_save_aspm_l1ss_state(struct pci_dev *pdev);
> I rebased this again on top of my pci/aspm updates to remove the need
> for the rename above.
>
>> +static void pci_save_aspm_state(struct pci_dev *dev)
>> +{
>> + struct pci_cap_saved_state *save_state;
>> + u16 *cap;
>> +
>> + if (!pci_is_pcie(dev))
>> + return;
>> +
>> + save_state = pci_find_saved_cap(dev, PCI_CAP_ID_EXP);
>> + if (!save_state)
>> + return;
>> +
>> + cap = (u16 *)&save_state->cap.data[0];
>> + pcie_capability_read_word(dev, PCI_EXP_LNKCTL, &cap[1]);
> And I changed this part so it only updates the PCI_EXP_LNKCTL_ASPMC
> bits, not the entire LNKCTL.
>
> Updating the entire saved register probably wouldn't *break* anything,
> but it could randomly hide other LNKCTL changes depending on whether
> or not ASPM configuration was changed in the interim. For example:
>
> - driver .probe() saves LNKCTL
> - LNKCTL changes some non-ASPMC thing via setpci or other mechanism
> - save_state updated via pcie_config_aspm_link()
>
> A restore in .slot_reset() would restore different LNKCTL values for
> the non-ASPMC change depending on whether pcie_config_aspm_link() was
> used.
>
> I applied it on pci/aspm for v6.9. Please take a look and make sure
> it still does what you need:
> https://git.kernel.org/pub/scm/linux/kernel/git/pci/pci.git/commit/?h=aspm&id=a6315434436d587f70e489e6365c5b7e20176a71
>
> Sathy and David, I didn't add your Reviewed-by because I didn't want
> to presume that you were OK with my changes. But I'd be more than
> happy to add them if you take a look.
Your update looks fine to me.
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
>
> Bjorn
>
>> +}
>> +
>> void pci_aspm_get_l1ss(struct pci_dev *pdev)
>> {
>> /* Read L1 PM substate capabilities */
>> pdev->l1ss = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_L1SS);
>> }
>>
>> -void pci_save_aspm_state(struct pci_dev *pdev)
>> +void pci_save_aspm_l1ss_state(struct pci_dev *pdev)
>> {
>> struct pci_cap_saved_state *save_state;
>> u16 l1ss = pdev->l1ss;
>> @@ -309,10 +325,12 @@ static void pcie_set_clkpm_nocheck(struct pcie_link_state *link, int enable)
>> struct pci_bus *linkbus = link->pdev->subordinate;
>> u32 val = enable ? PCI_EXP_LNKCTL_CLKREQ_EN : 0;
>>
>> - list_for_each_entry(child, &linkbus->devices, bus_list)
>> + list_for_each_entry(child, &linkbus->devices, bus_list) {
>> pcie_capability_clear_and_set_word(child, PCI_EXP_LNKCTL,
>> PCI_EXP_LNKCTL_CLKREQ_EN,
>> val);
>> + pci_save_aspm_state(child);
>> + }
>> link->clkpm_enabled = !!enable;
>> }
>>
>> @@ -931,6 +949,12 @@ static void pcie_config_aspm_link(struct pcie_link_state *link, u32 state)
>> pcie_config_aspm_dev(parent, upstream);
>>
>> link->aspm_enabled = state;
>> +
>> + /* Update latest ASPM configuration in saved context */
>> + pci_save_aspm_state(link->downstream);
>> + pci_save_aspm_l1ss_state(link->downstream);
>> + pci_save_aspm_state(parent);
>> + pci_save_aspm_l1ss_state(parent);
>> }
>>
>> static void pcie_config_aspm_path(struct pcie_link_state *link)
>> --
>> 2.25.1
>>
--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer
