Re: [PATCH V2] PCI/ASPM: Save/restore L1SS Capability for suspend/resume

From: Ben Chuang
Date: Fri Jul 15 2022 - 06:38:50 EST

On Tue, Jul 5, 2022 at 2:00 PM Vidya Sagar <vidyas@xxxxxxxxxx> wrote:
>
> Previously ASPM L1 Substates control registers (CTL1 and CTL2) weren't
> saved and restored during suspend/resume leading to L1 Substates
> configuration being lost post-resume.
>
> Save the L1 Substates control registers so that the configuration is
> retained post-resume.
>
> Signed-off-by: Vidya Sagar <vidyas@xxxxxxxxxx>
> Tested-by: Abhishek Sahu <abhsahu@xxxxxxxxxx>

Hi Vidya,

I tested this patch on kernel v5.19-rc6.
The test device is GL9755 card reader controller on Intel i5-10210U RVP.
This patch can restore L1SS after suspend/resume.

The test results are as follows:

After Boot:
#lspci -d 17a0:9755 -vvv | grep -A5 "L1 PM Substates"
Capabilities: [110 v1] L1 PM Substates
L1SubCap: PCI-PM_L1.2+ PCI-PM_L1.1+ ASPM_L1.2+
ASPM_L1.1+ L1_PM_Substates+
PortCommonModeRestoreTime=255us
PortTPowerOnTime=3100us
L1SubCtl1: PCI-PM_L1.2+ PCI-PM_L1.1+ ASPM_L1.2+ ASPM_L1.1+
T_CommonMode=0us LTR1.2_Threshold=3145728ns
L1SubCtl2: T_PwrOn=3100us


After suspend/resume without this patch.
#lspci -d 17a0:9755 -vvv | grep -A5 "L1 PM Substates"
Capabilities: [110 v1] L1 PM Substates
L1SubCap: PCI-PM_L1.2+ PCI-PM_L1.1+ ASPM_L1.2+
ASPM_L1.1+ L1_PM_Substates+
PortCommonModeRestoreTime=255us
PortTPowerOnTime=3100us
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


After suspend/resume with this patch.
#lspci -d 17a0:9755 -vvv | grep -A5 "L1 PM Substates"
Capabilities: [110 v1] L1 PM Substates
L1SubCap: PCI-PM_L1.2+ PCI-PM_L1.1+ ASPM_L1.2+
ASPM_L1.1+ L1_PM_Substates+
PortCommonModeRestoreTime=255us
PortTPowerOnTime=3100us
L1SubCtl1: PCI-PM_L1.2+ PCI-PM_L1.1+ ASPM_L1.2+ ASPM_L1.1+
T_CommonMode=0us LTR1.2_Threshold=3145728ns
L1SubCtl2: T_PwrOn=3100us


Tested-by: Ben Chuang <benchuanggli@xxxxxxxxx>

Best regards,
Ben Chuang


> ---
> Hi,
> Kenneth R. Crudup <kenny@xxxxxxxxx>, Could you please verify this patch
> on your laptop (Dell XPS 13) one last time?
> IMHO, the regression observed on your laptop with an old version of the patch
> could be due to a buggy old version BIOS in the laptop.
>
> Thanks,
> Vidya Sagar
>
> drivers/pci/pci.c | 7 +++++++
> drivers/pci/pci.h | 4 ++++
> drivers/pci/pcie/aspm.c | 44 +++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 55 insertions(+)
>
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index cfaf40a540a8..aca05880aaa3 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -1667,6 +1667,7 @@ int pci_save_state(struct pci_dev *dev)
> return i;
>
> pci_save_ltr_state(dev);
> + pci_save_aspm_l1ss_state(dev);
> pci_save_dpc_state(dev);
> pci_save_aer_state(dev);
> pci_save_ptm_state(dev);
> @@ -1773,6 +1774,7 @@ void pci_restore_state(struct pci_dev *dev)
> * LTR itself (in the PCIe capability).
> */
> pci_restore_ltr_state(dev);
> + pci_restore_aspm_l1ss_state(dev);
>
> pci_restore_pcie_state(dev);
> pci_restore_pasid_state(dev);
> @@ -3489,6 +3491,11 @@ void pci_allocate_cap_save_buffers(struct pci_dev *dev)
> if (error)
> pci_err(dev, "unable to allocate suspend buffer for LTR\n");
>
> + error = pci_add_ext_cap_save_buffer(dev, PCI_EXT_CAP_ID_L1SS,
> + 2 * sizeof(u32));
> + if (error)
> + pci_err(dev, "unable to allocate suspend buffer for ASPM-L1SS\n");
> +
> pci_allocate_vc_save_buffers(dev);
> }
>
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index e10cdec6c56e..92d8c92662a4 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -562,11 +562,15 @@ void pcie_aspm_init_link_state(struct pci_dev *pdev);
> void pcie_aspm_exit_link_state(struct pci_dev *pdev);
> void pcie_aspm_pm_state_change(struct pci_dev *pdev);
> void pcie_aspm_powersave_config_link(struct pci_dev *pdev);
> +void pci_save_aspm_l1ss_state(struct pci_dev *dev);
> +void pci_restore_aspm_l1ss_state(struct pci_dev *dev);
> #else
> static inline void pcie_aspm_init_link_state(struct pci_dev *pdev) { }
> static inline void pcie_aspm_exit_link_state(struct pci_dev *pdev) { }
> static inline void pcie_aspm_pm_state_change(struct pci_dev *pdev) { }
> static inline void pcie_aspm_powersave_config_link(struct pci_dev *pdev) { }
> +static inline void pci_save_aspm_l1ss_state(struct pci_dev *dev) { }
> +static inline void pci_restore_aspm_l1ss_state(struct pci_dev *dev) { }
> #endif
>
> #ifdef CONFIG_PCIE_ECRC
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index a96b7424c9bc..2c29fdd20059 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -726,6 +726,50 @@ static void pcie_config_aspm_l1ss(struct pcie_link_state *link, u32 state)
> PCI_L1SS_CTL1_L1SS_MASK, val);
> }
>
> +void pci_save_aspm_l1ss_state(struct pci_dev *dev)
> +{
> + int aspm_l1ss;
> + struct pci_cap_saved_state *save_state;
> + u32 *cap;
> +
> + if (!pci_is_pcie(dev))
> + return;
> +
> + aspm_l1ss = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_L1SS);
> + if (!aspm_l1ss)
> + return;
> +
> + save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_L1SS);
> + if (!save_state)
> + return;
> +
> + cap = (u32 *)&save_state->cap.data[0];
> + pci_read_config_dword(dev, aspm_l1ss + PCI_L1SS_CTL2, cap++);
> + pci_read_config_dword(dev, aspm_l1ss + PCI_L1SS_CTL1, cap++);
> +}
> +
> +void pci_restore_aspm_l1ss_state(struct pci_dev *dev)
> +{
> + int aspm_l1ss;
> + struct pci_cap_saved_state *save_state;
> + u32 *cap;
> +
> + if (!pci_is_pcie(dev))
> + return;
> +
> + aspm_l1ss = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_L1SS);
> + if (!aspm_l1ss)
> + return;
> +
> + save_state = pci_find_saved_ext_cap(dev, PCI_EXT_CAP_ID_L1SS);
> + if (!save_state)
> + return;
> +
> + cap = (u32 *)&save_state->cap.data[0];
> + pci_write_config_dword(dev, aspm_l1ss + PCI_L1SS_CTL2, *cap++);
> + pci_write_config_dword(dev, aspm_l1ss + PCI_L1SS_CTL1, *cap++);
> +}
> +
> static void pcie_config_aspm_dev(struct pci_dev *pdev, u32 val)
> {
> pcie_capability_clear_and_set_word(pdev, PCI_EXP_LNKCTL,
> --
> 2.17.1
>