[PATCH v6 1/3] PCI/ASPM: Use pcie_capability_clear_and_set_word() for ASPM disable/restore

[Krishna Chaitanya Chundru]

pcie_aspm_cap_init() disables ASPM L0s/L1 on both ends of the Link
before touching L1SS config, then later restores the LNKCTL state
that was in effect beforehand. Both steps use raw
pcie_capability_write_word() calls: the disable step computes the
new value by hand from a snapshot taken earlier in the function, and
the restore step writes that same snapshot straight back.

Switch both steps to pcie_capability_clear_and_set_word(), masked to
PCI_EXP_LNKCTL_ASPMC, matching the accessor pcie_config_aspm_dev()
already uses elsewhere in this file for the exact same register. This
does a live read-modify-write of just the ASPM Control bits instead of
relying on a stale snapshot for the rest of the word, and is
consistent with how the rest of the file already touches this
register. No functional change.

Fixes: 7447990137bf ("PCI/ASPM: Disable L1 before disabling L1 PM Substates")
Signed-off-by: Krishna Chaitanya Chundru <krishna.chundru@xxxxxxxxxxxxxxxx>
---
 drivers/pci/pcie/aspm.c | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 172783e7f519..3f9c0f9a1cc7 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -894,10 +894,10 @@ static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
 	/* Disable L0s/L1 before updating L1SS config */
 	if (FIELD_GET(PCI_EXP_LNKCTL_ASPMC, child_lnkctl) ||
 	    FIELD_GET(PCI_EXP_LNKCTL_ASPMC, parent_lnkctl)) {
-		pcie_capability_write_word(child, PCI_EXP_LNKCTL,
-					   child_lnkctl & ~PCI_EXP_LNKCTL_ASPMC);
-		pcie_capability_write_word(parent, PCI_EXP_LNKCTL,
-					   parent_lnkctl & ~PCI_EXP_LNKCTL_ASPMC);
+		pcie_capability_clear_and_set_word(child, PCI_EXP_LNKCTL,
+						   PCI_EXP_LNKCTL_ASPMC, 0);
+		pcie_capability_clear_and_set_word(parent, PCI_EXP_LNKCTL,
+						   PCI_EXP_LNKCTL_ASPMC, 0);
 	}
 
 	/*
@@ -927,8 +927,12 @@ static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
 	/* Restore L0s/L1 if they were enabled */
 	if (FIELD_GET(PCI_EXP_LNKCTL_ASPMC, child_lnkctl) ||
 	    FIELD_GET(PCI_EXP_LNKCTL_ASPMC, parent_lnkctl)) {
-		pcie_capability_write_word(parent, PCI_EXP_LNKCTL, parent_lnkctl);
-		pcie_capability_write_word(child, PCI_EXP_LNKCTL, child_lnkctl);
+		pcie_capability_clear_and_set_word(parent, PCI_EXP_LNKCTL,
+						   PCI_EXP_LNKCTL_ASPMC,
+						   parent_lnkctl & PCI_EXP_LNKCTL_ASPMC);
+		pcie_capability_clear_and_set_word(child, PCI_EXP_LNKCTL,
+						   PCI_EXP_LNKCTL_ASPMC,
+						   child_lnkctl & PCI_EXP_LNKCTL_ASPMC);
 	}
 
 	/* Save default state */

-- 
2.34.1