[SRU][R][PATCH 1/3] PCI/ASPM: Cache L0s/L1 Supported so advertised link states can be overridden

[AceLan Kao]

From: Bjorn Helgaas <bhelgaas at google.com>

BugLink: https://bugs.launchpad.net/bugs/2166737

Defective devices sometimes advertise support for ASPM L0s or L1 states
even if they don't work correctly.

Cache the L0s Supported and L1 Supported bits early in enumeration so
HEADER quirks can override the ASPM states advertised in Link Capabilities
before pcie_aspm_cap_init() enables ASPM.

Signed-off-by: Bjorn Helgaas <bhelgaas at google.com>
Tested-by: Shawn Lin <shawn.lin at rock-chips.com>
Reviewed-by: Lukas Wunner <lukas at wunner.de>
Link: https://patch.msgid.link/20251110222929.2140564-2-helgaas@kernel.org
(cherry picked from commit 4495bffd86ba0fdabfaef0c41d12f68ec2a1e05b)
Signed-off-by: Chia-Lin Kao (AceLan) <acelan.kao at canonical.com>
---
 drivers/pci/pcie/aspm.c | 12 ++++--------
 drivers/pci/probe.c     |  7 +++++++
 include/linux/pci.h     |  2 ++
 3 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index e3992133390b1..2454f97eea7ce 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -798,7 +798,6 @@ static void aspm_l1ss_init(struct pcie_link_state *link)
 static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
 {
 	struct pci_dev *child = link->downstream, *parent = link->pdev;
-	u32 parent_lnkcap, child_lnkcap;
 	u16 parent_lnkctl, child_lnkctl;
 	struct pci_bus *linkbus = parent->subordinate;
 
@@ -813,9 +812,8 @@ static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
 	 * If ASPM not supported, don't mess with the clocks and link,
 	 * bail out now.
 	 */
-	pcie_capability_read_dword(parent, PCI_EXP_LNKCAP, &parent_lnkcap);
-	pcie_capability_read_dword(child, PCI_EXP_LNKCAP, &child_lnkcap);
-	if (!(parent_lnkcap & child_lnkcap & PCI_EXP_LNKCAP_ASPMS))
+	if (!(parent->aspm_l0s_support && child->aspm_l0s_support) &&
+	    !(parent->aspm_l1_support && child->aspm_l1_support))
 		return;
 
 	/* Configure common clock before checking latencies */
@@ -827,8 +825,6 @@ static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
 	 * read-only Link Capabilities may change depending on common clock
 	 * configuration (PCIe r5.0, sec 7.5.3.6).
 	 */
-	pcie_capability_read_dword(parent, PCI_EXP_LNKCAP, &parent_lnkcap);
-	pcie_capability_read_dword(child, PCI_EXP_LNKCAP, &child_lnkcap);
 	pcie_capability_read_word(parent, PCI_EXP_LNKCTL, &parent_lnkctl);
 	pcie_capability_read_word(child, PCI_EXP_LNKCTL, &child_lnkctl);
 
@@ -848,7 +844,7 @@ static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
 	 * given link unless components on both sides of the link each
 	 * support L0s.
 	 */
-	if (parent_lnkcap & child_lnkcap & PCI_EXP_LNKCAP_ASPM_L0S)
+	if (parent->aspm_l0s_support && child->aspm_l0s_support)
 		link->aspm_support |= PCIE_LINK_STATE_L0S;
 
 	if (child_lnkctl & PCI_EXP_LNKCTL_ASPM_L0S)
@@ -857,7 +853,7 @@ static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
 		link->aspm_enabled |= PCIE_LINK_STATE_L0S_DW;
 
 	/* Setup L1 state */
-	if (parent_lnkcap & child_lnkcap & PCI_EXP_LNKCAP_ASPM_L1)
+	if (parent->aspm_l1_support && child->aspm_l1_support)
 		link->aspm_support |= PCIE_LINK_STATE_L1;
 
 	if (parent_lnkctl & child_lnkctl & PCI_EXP_LNKCTL_ASPM_L1)
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index feefda64b8745..17cbd70c56379 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -1613,6 +1613,13 @@ void set_pcie_port_type(struct pci_dev *pdev)
 	if (reg32 & PCI_EXP_LNKCAP_DLLLARC)
 		pdev->link_active_reporting = 1;
 
+#ifdef CONFIG_PCIEASPM
+	if (reg32 & PCI_EXP_LNKCAP_ASPM_L0S)
+		pdev->aspm_l0s_support = 1;
+	if (reg32 & PCI_EXP_LNKCAP_ASPM_L1)
+		pdev->aspm_l1_support = 1;
+#endif
+
 	parent = pci_upstream_bridge(pdev);
 	if (!parent)
 		return;
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 9dcccd5d8e824..a1fee1a73b045 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -410,6 +410,8 @@ struct pci_dev {
 	u16		l1ss;		/* L1SS Capability pointer */
 #ifdef CONFIG_PCIEASPM
 	struct pcie_link_state	*link_state;	/* ASPM link state */
+	unsigned int	aspm_l0s_support:1;	/* ASPM L0s support */
+	unsigned int	aspm_l1_support:1;	/* ASPM L1 support */
 	unsigned int	ltr_path:1;	/* Latency Tolerance Reporting
 					   supported from root to here */
 #endif
-- 
2.53.0