[PATCH 7/7][Noble] PCI/ASPM: Update save_state when configuration changes

[AceLan Kao]

From: Vidya Sagar <vidyas at nvidia.com>

BugLink: https://bugs.launchpad.net/bugs/2042500

Many PCIe device drivers save the configuration state of their device
during probe and restore it when their .slot_reset() hook is called during
PCIe error recovery.

If the ASPM configuration is changed after the driver's probe is called and
before an error event occurs, .slot_reset() restores the ASPM configuration
to what it was at the time of probe, not to what it was just before the
occurrence of the error event.  This leads to a mismatch in ASPM
configuration between the device and its upstream device.

Update the saved configuration of the device when the ASPM configuration
changes.

Link: https://lore.kernel.org/r/20240222174436.3565146-1-vidyas@nvidia.com
Signed-off-by: Vidya Sagar <vidyas at nvidia.com>
[bhelgaas: commit log, rebase to pci/aspm, rename to
pci_update_aspm_saved_state() since it updates only LNKCTL, update only
ASPMC and CLKREQ_EN in LNKCTL]
Signed-off-by: Bjorn Helgaas <bhelgaas at google.com>
Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy at linux.intel.com>
Reviewed-by: David E. Box <david.e.box at linux.intel.com>
(cherry picked from commit 6d4266675279b38c301243f3a4fac4a511b03246)
Signed-off-by: Chia-Lin Kao (AceLan) <acelan.kao at canonical.com>
---
 drivers/pci/pcie/aspm.c | 34 +++++++++++++++++++++++++++++++++-
 1 file changed, 33 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 43447e356490..42fe18e4f8a9 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -301,16 +301,42 @@ static int policy_to_clkpm_state(struct pcie_link_state *link)
 	return 0;
 }
 
+static void pci_update_aspm_saved_state(struct pci_dev *dev)
+{
+	struct pci_cap_saved_state *save_state;
+	u16 *cap, lnkctl, aspm_ctl;
+
+	save_state = pci_find_saved_cap(dev, PCI_CAP_ID_EXP);
+	if (!save_state)
+		return;
+
+	pcie_capability_read_word(dev, PCI_EXP_LNKCTL, &lnkctl);
+
+	/*
+	 * Update ASPM and CLKREQ bits of LNKCTL in save_state. We only
+	 * write PCI_EXP_LNKCTL_CCC during enumeration, so it shouldn't
+	 * change after being captured in save_state.
+	 */
+	aspm_ctl = lnkctl & (PCI_EXP_LNKCTL_ASPMC | PCI_EXP_LNKCTL_CLKREQ_EN);
+	lnkctl &= ~(PCI_EXP_LNKCTL_ASPMC | PCI_EXP_LNKCTL_CLKREQ_EN);
+
+	/* Depends on pci_save_pcie_state(): cap[1] is LNKCTL */
+	cap = (u16 *)&save_state->cap.data[0];
+	cap[1] = lnkctl | aspm_ctl;
+}
+
 static void pcie_set_clkpm_nocheck(struct pcie_link_state *link, int enable)
 {
 	struct pci_dev *child;
 	struct pci_bus *linkbus = link->pdev->subordinate;
 	u32 val = enable ? PCI_EXP_LNKCTL_CLKREQ_EN : 0;
 
-	list_for_each_entry(child, &linkbus->devices, bus_list)
+	list_for_each_entry(child, &linkbus->devices, bus_list) {
 		pcie_capability_clear_and_set_word(child, PCI_EXP_LNKCTL,
 						   PCI_EXP_LNKCTL_CLKREQ_EN,
 						   val);
+		pci_update_aspm_saved_state(child);
+	}
 	link->clkpm_enabled = !!enable;
 }
 
@@ -929,6 +955,12 @@ static void pcie_config_aspm_link(struct pcie_link_state *link, u32 state)
 		pcie_config_aspm_dev(parent, upstream);
 
 	link->aspm_enabled = state;
+
+	/* Update latest ASPM configuration in saved context */
+	pci_save_aspm_l1ss_state(link->downstream);
+	pci_update_aspm_saved_state(link->downstream);
+	pci_save_aspm_l1ss_state(parent);
+	pci_update_aspm_saved_state(parent);
 }
 
 static void pcie_config_aspm_path(struct pcie_link_state *link)
-- 
2.34.1