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PCI/ASPM: Ignore L1 PM Substates if device lacks capability 

187f91db82 ("PCI/ASPM: Remove struct aspm_register_info.l1ss_cap")
inadvertently removed a check for existence of the L1 PM Substates (L1SS)
Capability before reading it.

If there is no L1SS Capability, this means we mistakenly read PCI_COMMAND
and PCI_STATUS (config address 0x04) and interpret that as the PCI_L1SS_CAP
register, so we may incorrectly configure L1SS.

Make sure the L1SS Capability exists before trying to read it.

Fixes: 187f91db82 ("PCI/ASPM: Remove struct aspm_register_info.l1ss_cap")
Link: https://lore.kernel.org/r/20221005025809.2247547-3-helgaas@kernel.org
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
This commit is contained in:
Bjorn Helgaas 2022-10-04 21:58:08 -05:00
parent 9e2a03173d
commit cfc0028627
1 changed files with 3 additions and 0 deletions
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3
drivers/pci/pcie/aspm.c
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@ -560,6 +560,9 @@ static void aspm_l1ss_init(struct pcie_link_state *link)
u32 parent_l1ss_cap, child_l1ss_cap;
u32 parent_l1ss_ctl1 = 0, child_l1ss_ctl1 = 0;
if (!parent->l1ss || !child->l1ss)
return;
/* Setup L1 substate */
pci_read_config_dword(parent, parent->l1ss + PCI_L1SS_CAP,
&parent_l1ss_cap);