Re: [PATCH v3 3/3] PCI/ASPM: Fix L1SS parameters & only enable supported features when enable link state

Ilpo Järvinen
2024-02-07T12:54:33Z

On Wed, 7 Feb 2024, Jian-Hong Pan wrote:

> The original __pci_enable_link_state() configs the links directly without:
> * Check the L1 substates features which are supported, or not
> * Calculate & program related parameters for L1.2, such as T_POWER_ON,
> Common_Mode_Restore_Time, and LTR_L1.2_THRESHOLD
>
> This leads some supported L1 PM substates of the link between VMD remapped
> PCIe Root Port and NVMe get wrong configs when a caller tries to enabled
> them.
>
> Here is a failed example on ASUS B1400CEAE with enabled VMD:
>
> Capabilities: [900 v1] L1 PM Substates
> L1SubCap: PCI-PM_L1.2+ PCI-PM_L1.1- ASPM_L1.2+ ASPM_L1.1- L1_PM_Substates+
> PortCommonModeRestoreTime=32us PortTPowerOnTime=10us
> L1SubCtl1: PCI-PM_L1.2- PCI-PM_L1.1- ASPM_L1.2+ ASPM_L1.1-
> T_CommonMode=0us LTR1.2_Threshold=0ns
> L1SubCtl2: T_PwrOn=10us
>
> This patch initializes the link's L1 PM substates to get the supported
> features and programs relating paramters, if some of them are going to be
> enabled in __pci_enable_link_state(). Then, enables the L1 PM substates if
> the caller intends to enable them and they are supported.
>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=218394
> Signed-off-by: Jian-Hong Pan <jhp@endlessos.org>
> ---
> v2:
> - Prepare the PCIe LTR parameters before enable L1 Substates
>
> v3:
> - Only enable supported features for the L1 Substates part
>
> drivers/pci/pcie/aspm.c | 12 +++++++-----
> 1 file changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index a39d2ee744cb..c866971cae70 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -1389,14 +1389,16 @@ static int __pci_enable_link_state(struct pci_dev *pdev, int state, bool locked)
> link->aspm_default |= ASPM_STATE_L0S;
> if (state & PCIE_LINK_STATE_L1)
> link->aspm_default |= ASPM_STATE_L1;
> - /* L1 PM substates require L1 */
> - if (state & PCIE_LINK_STATE_L1_1)
> + if (state & ASPM_STATE_L1_2_MASK)
> + aspm_l1ss_init(link);

Your commit message didn't explain why you need to add this call here, why
isn't the existing call to aspm_l1ss_init() enough to initialize what is
needed?

> + /* L1 PM substates require L1 and should be in supported list */
> + if (state & link->aspm_support & PCIE_LINK_STATE_L1_1)
> link->aspm_default |= ASPM_STATE_L1_1 | ASPM_STATE_L1;
> - if (state & PCIE_LINK_STATE_L1_2)
> + if (state & link->aspm_support & PCIE_LINK_STATE_L1_2)
> link->aspm_default |= ASPM_STATE_L1_2 | ASPM_STATE_L1;
> - if (state & PCIE_LINK_STATE_L1_1_PCIPM)
> + if (state & link->aspm_support & PCIE_LINK_STATE_L1_1_PCIPM)
> link->aspm_default |= ASPM_STATE_L1_1_PCIPM | ASPM_STATE_L1;
> - if (state & PCIE_LINK_STATE_L1_2_PCIPM)
> + if (state & link->aspm_support & PCIE_LINK_STATE_L1_2_PCIPM)
> link->aspm_default |= ASPM_STATE_L1_2_PCIPM | ASPM_STATE_L1;

It would be simpler and cleaner to just AND once with link->aspm_support
to clear unsupported bits from state rather than doing it on every line
like that.

--
i.