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

187f91db8237 ("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: 187f91db8237 ("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>

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 4535228e4a64f62a7431ca5a1d659caf570c8633..f12d117f44e0582eb9f0d211d0cfa18d98e19b80 100644 (file)
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -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);