Re: [PATCH v12 3/3] PCI/ASPM: Make pci_save_aspm_l1ss_state save both child and parent's L1SS configuration

[Ilpo Järvinen]

On Tue, 1 Oct 2024, David E. Box wrote:

> Hi Jian-Hong,
> 
> On Tue, 2024-10-01 at 16:34 +0800, Jian-Hong Pan wrote:
> > PCI devices' parameters on the VMD bus have been programmed properly
> > originally. But, cleared after pci_reset_bus() and have not been restored
> > correctly. This leads the link's L1.2 between PCIe Root Port and child
> > device gets wrong configs.
> > 
> > Here is a failed example on ASUS B1400CEAE with enabled VMD. Both PCIe
> > bridge and NVMe device should have the same LTR1.2_Threshold value.
> > However, they are configured as different values in this case:
> > 
> > 10000:e0:06.0 PCI bridge [0604]: Intel Corporation 11th Gen Core Processor
> > PCIe Controller [8086:9a09] (rev 01) (prog-if 00 [Normal decode])
> >   ...
> >   Capabilities: [200 v1] L1 PM Substates
> >     L1SubCap: PCI-PM_L1.2+ PCI-PM_L1.1+ ASPM_L1.2+ ASPM_L1.1+ L1_PM_Substates+
> >       PortCommonModeRestoreTime=45us PortTPowerOnTime=50us
> >     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=0us
> > 
> > 10000:e1:00.0 Non-Volatile memory controller [0108]: Sandisk Corp WD Blue
> > SN550 NVMe SSD [15b7:5009] (rev 01) (prog-if 02 [NVM Express])
> >   ...
> >   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=101376ns
> >     L1SubCtl2: T_PwrOn=50us
> > 
> > Here is VMD mapped PCI device tree:
> > 
> > -+-[0000:00]-+-00.0  Intel Corporation Device 9a04
> >  | ...
> >  \-[10000:e0]-+-06.0-[e1]----00.0  Sandisk Corp WD Blue SN550 NVMe SSD
> >               \-17.0  Intel Corporation Tiger Lake-LP SATA Controller
> > 
> > When pci_reset_bus() resets the bus [e1] of the NVMe, it only saves and
> > restores NVMe's state before and after reset. Then, when it restores the
> > NVMe's state, ASPM code restores L1SS for both the parent bridge and the
> > NVMe in pci_restore_aspm_l1ss_state(). The NVMe's L1SS is restored
> > correctly. But, the parent bridge's L1SS is restored with a wrong value 0x0
> > because the parent bridge's L1SS wasn't saved by pci_save_aspm_l1ss_state()
> > before reset.
> > 
> > So, if the PCI device has a parent, make pci_save_aspm_l1ss_state() save
> > the parent's L1SS configuration, too. This is symmetric on
> > pci_restore_aspm_l1ss_state().
> > 
> > Link:
> > https://lore.kernel.org/linux-pci/CAPpJ_eexU0gCHMbXw_z924WxXw0+B6SdS4eG9oGpEX1wmnMLkQ@xxxxxxxxxxxxxx/
> > Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218394
> > Fixes: 17423360a27a ("PCI/ASPM: Save L1 PM Substates Capability for
> > suspend/resume")
> > Suggested-by: Ilpo Järvinen <ilpo.jarvinen@xxxxxxxxxxxxxxx>
> > Signed-off-by: Jian-Hong Pan <jhp@xxxxxxxxxxxxx>
> > ---
> > v9:
> > - Drop the v8 fix about drivers/pci/pcie/aspm.c. Use this in VMD instead.
> > 
> > v10:
> > - Drop the v9 fix about drivers/pci/controller/vmd.c
> > - Fix in PCIe ASPM to make it symmetric between pci_save_aspm_l1ss_state()
> >   and pci_restore_aspm_l1ss_state()
> > 
> > v11:
> > - Introduce __pci_save_aspm_l1ss_state as a resusable helper function
> >   which is same as the original pci_configure_aspm_l1ss
> > - Make pci_save_aspm_l1ss_state invoke __pci_save_aspm_l1ss_state for
> >   both child and parent devices
> > - Smooth the commit message
> > 
> > v12:
> > - Update the commit message
> > 
> >  drivers/pci/pcie/aspm.c | 20 +++++++++++++++++++-
> >  1 file changed, 19 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> > index bd0a8a05647e..17cdf372f7e0 100644
> > --- a/drivers/pci/pcie/aspm.c
> > +++ b/drivers/pci/pcie/aspm.c
> > @@ -79,7 +79,7 @@ void pci_configure_aspm_l1ss(struct pci_dev *pdev)
> >  			ERR_PTR(rc));
> >  }
> >  
> > -void pci_save_aspm_l1ss_state(struct pci_dev *pdev)
> > +static void __pci_save_aspm_l1ss_state(struct pci_dev *pdev)
> >  {
> >  	struct pci_cap_saved_state *save_state;
> >  	u16 l1ss = pdev->l1ss;
> > @@ -101,6 +101,24 @@ void pci_save_aspm_l1ss_state(struct pci_dev *pdev)
> >  	pci_read_config_dword(pdev, l1ss + PCI_L1SS_CTL1, cap++);
> >  }
> >  
> > +void pci_save_aspm_l1ss_state(struct pci_dev *pdev)
> > +{
> > +	struct pci_dev *parent;
> > +
> > +	__pci_save_aspm_l1ss_state(pdev);
> > +
> > +	/*
> > +	 * To be symmetric on pci_restore_aspm_l1ss_state(), save parent's L1
> > +	 * substate configuration, if the parent has not saved state.
> > +	 */
> > +	if (!pdev->bus || !pdev->bus->self)
> > +		return;
> > +
> > +	parent = pdev->bus->self;
> > +	if (!parent->state_saved)
> > +		__pci_save_aspm_l1ss_state(parent);
> > +}
> > +
> >  void pci_restore_aspm_l1ss_state(struct pci_dev *pdev)
> >  {
> >  	struct pci_cap_saved_state *pl_save_state, *cl_save_state;
> 
> This took a while to debug and find a solution. Thanks for continuing to work on
> this.
> 
> Reviewed-by: David E. Box <david.e.box@xxxxxxxxxxxxxxx

The tag is missing the closing >. 

Repeating the correct one here for the purpose of patchwork to pick up the 
correct tag:

Reviewed-by: David E. Box <david.e.box@xxxxxxxxxxxxxxx>

...But I suppose patchwork might now record both the wrong and the correct 
tag so heads up to maintainers if applying this version of the patch.

-- 
 i.