[PATCH 07/15] PCI/ASPM: Save L1SS state in the saved capability store

[David Matlack <dmatlack@google.com>]

Save and restore the L1 PM Substates control registers through the
per-device saved capability store instead of a private pci_cap_saved_state
buffer.

pci_restore_aspm_l1ss_state() needs both the Upstream and Downstream
Port's saved L1SS configuration, and had to fetch two buffers and decode
each by index. Read the saved values by configuration space offset
instead, which names the register at every use. Add
pci_read_saved_l1ss_ctl() to read one device's pair, so that the Port
and the device below it are read the same way.

Reserve PCI_L1SS_CTL1 and PCI_L1SS_CTL2 with a single request, since
they are adjacent DWORDs, just as the old code allocated one two-DWORD
buffer for both. Skip the reservation entirely for devices without the
capability, which the previous code could not do because it allocated
the buffer through pci_add_ext_cap_save_buffer() before looking at
pdev->l1ss.

No functional change intended.

Assisted-by: LLM
Signed-off-by: David Matlack <dmatlack@google.com>
---
 drivers/pci/pcie/aspm.c | 52 +++++++++++++++++------------------------
 1 file changed, 22 insertions(+), 30 deletions(-)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 16f22af98686..9d64c6aebb9f 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -59,19 +59,19 @@ void pci_configure_aspm_l1ss(struct pci_dev *pdev)
 	int rc;
 
 	pdev->l1ss = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_L1SS);
+	if (!pdev->l1ss)
+		return;
 
-	rc = pci_add_ext_cap_save_buffer(pdev, PCI_EXT_CAP_ID_L1SS,
-					 2 * sizeof(u32));
+	/* PCI_L1SS_CTL1 and PCI_L1SS_CTL2 are adjacent DWORDs */
+	rc = pci_reserve_saved_cap(pdev, pdev->l1ss + PCI_L1SS_CTL1, 2 * sizeof(u32));
 	if (rc)
-		pci_err(pdev, "unable to allocate ASPM L1SS save buffer (%pe)\n",
+		pci_err(pdev, "unable to reserve ASPM L1SS save state (%pe)\n",
 			ERR_PTR(rc));
 }
 
 void pci_save_aspm_l1ss_state(struct pci_dev *pdev)
 {
 	struct pci_dev *parent = pdev->bus->self;
-	struct pci_cap_saved_state *save_state;
-	u32 *cap;
 
 	/*
 	 * If this is a Downstream Port, we never restore the L1SS state
@@ -88,32 +88,32 @@ void pci_save_aspm_l1ss_state(struct pci_dev *pdev)
 	 * Save L1 substate configuration. The ASPM L0s/L1 configuration
 	 * in PCI_EXP_LNKCTL_ASPMC is saved by pci_save_pcie_state().
 	 */
-	save_state = pci_find_saved_ext_cap(pdev, PCI_EXT_CAP_ID_L1SS);
-	if (!save_state)
-		return;
-
-	cap = &save_state->cap.data[0];
-	pci_read_config_dword(pdev, pdev->l1ss + PCI_L1SS_CTL2, cap++);
-	pci_read_config_dword(pdev, pdev->l1ss + PCI_L1SS_CTL1, cap++);
+	pci_save_cap_dword(pdev, pdev->l1ss + PCI_L1SS_CTL2);
+	pci_save_cap_dword(pdev, pdev->l1ss + PCI_L1SS_CTL1);
 
 	/*
 	 * Save parent's L1 substate configuration so we have it for
 	 * pci_restore_aspm_l1ss_state(pdev) to restore.
 	 */
-	save_state = pci_find_saved_ext_cap(parent, PCI_EXT_CAP_ID_L1SS);
-	if (!save_state)
-		return;
+	pci_save_cap_dword(parent, parent->l1ss + PCI_L1SS_CTL2);
+	pci_save_cap_dword(parent, parent->l1ss + PCI_L1SS_CTL1);
+}
 
-	cap = &save_state->cap.data[0];
-	pci_read_config_dword(parent, parent->l1ss + PCI_L1SS_CTL2, cap++);
-	pci_read_config_dword(parent, parent->l1ss + PCI_L1SS_CTL1, cap++);
+/*
+ * Read a device's saved L1 substate configuration.
+ *
+ * Return: true if both registers had a saved value, false otherwise.
+ */
+static bool pci_read_saved_l1ss_ctl(struct pci_dev *dev, u32 *ctl1, u32 *ctl2)
+{
+	return pci_read_saved_cap_dword(dev, dev->l1ss + PCI_L1SS_CTL1, ctl1) &&
+	       pci_read_saved_cap_dword(dev, dev->l1ss + PCI_L1SS_CTL2, ctl2);
 }
 
 void pci_restore_aspm_l1ss_state(struct pci_dev *pdev)
 {
-	struct pci_cap_saved_state *pl_save_state, *cl_save_state;
 	struct pci_dev *parent = pdev->bus->self;
-	u32 *cap, pl_ctl1, pl_ctl2, pl_l1_2_enable;
+	u32 pl_ctl1, pl_ctl2, pl_l1_2_enable;
 	u32 cl_ctl1, cl_ctl2, cl_l1_2_enable;
 	u16 clnkctl, plnkctl;
 
@@ -128,18 +128,10 @@ void pci_restore_aspm_l1ss_state(struct pci_dev *pdev)
 	if (!pdev->l1ss || !parent->l1ss)
 		return;
 
-	cl_save_state = pci_find_saved_ext_cap(pdev, PCI_EXT_CAP_ID_L1SS);
-	pl_save_state = pci_find_saved_ext_cap(parent, PCI_EXT_CAP_ID_L1SS);
-	if (!cl_save_state || !pl_save_state)
+	if (!pci_read_saved_l1ss_ctl(pdev, &cl_ctl1, &cl_ctl2) ||
+	    !pci_read_saved_l1ss_ctl(parent, &pl_ctl1, &pl_ctl2))
 		return;
 
-	cap = &cl_save_state->cap.data[0];
-	cl_ctl2 = *cap++;
-	cl_ctl1 = *cap;
-	cap = &pl_save_state->cap.data[0];
-	pl_ctl2 = *cap++;
-	pl_ctl1 = *cap;
-
 	/* Make sure L0s/L1 are disabled before updating L1SS config */
 	pcie_capability_read_word(pdev, PCI_EXP_LNKCTL, &clnkctl);
 	pcie_capability_read_word(parent, PCI_EXP_LNKCTL, &plnkctl);
-- 
2.56.0.rc1.315.gc6ed9934b7-goog