Revert "PCI/ASPM: Refactor L1 PM Substates Control Register programming"

This reverts commit 5e85eba6.

Thomas Witt reported that 5e85eba6 ("PCI/ASPM: Refactor L1 PM Substates
Control Register programming") broke suspend/resume on a Tuxedo
Infinitybook S 14 v5, which seems to use a Clevo L140CU Mainboard.

The main symptom is:

  iwlwifi 0000:02:00.0: Unable to change power state from D3hot to D0, device inaccessible
  nvme 0000:03:00.0: Unable to change power state from D3hot to D0, device inaccessible

and the machine is only partially usable after resume.  It can't run dmesg
and can't do a clean reboot.  This happens on every suspend/resume cycle.

Revert 5e85eba6 until we can figure out the root cause.

Fixes: 5e85eba6 ("PCI/ASPM: Refactor L1 PM Substates Control Register programming")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=216877Reported-by: NThomas Witt <kernel@witt.link>
Tested-by: NThomas Witt <kernel@witt.link>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Cc: stable@vger.kernel.org	# v6.1+
Cc: Vidya Sagar <vidyas@nvidia.com>

drivers/pci/pcie/aspm.c

@@ -470,31 +470,6 @@ static void pci_clear_and_set_dword(struct pci_dev *pdev, int pos,
 	pci_write_config_dword(pdev, pos, val);
 }
 
-static void aspm_program_l1ss(struct pci_dev *dev, u32 ctl1, u32 ctl2)
-{
-	u16 l1ss = dev->l1ss;
-	u32 l1_2_enable;
-
-	/*
-	 * Per PCIe r6.0, sec 5.5.4, T_POWER_ON in PCI_L1SS_CTL2 must be
-	 * programmed prior to setting the L1.2 enable bits in PCI_L1SS_CTL1.
-	 */
-	pci_write_config_dword(dev, l1ss + PCI_L1SS_CTL2, ctl2);
-
-	/*
-	 * In addition, Common_Mode_Restore_Time and LTR_L1.2_THRESHOLD in
-	 * PCI_L1SS_CTL1 must be programmed *before* setting the L1.2
-	 * enable bits, even though they're all in PCI_L1SS_CTL1.
-	 */
-	l1_2_enable = ctl1 & PCI_L1SS_CTL1_L1_2_MASK;
-	ctl1 &= ~PCI_L1SS_CTL1_L1_2_MASK;
-
-	pci_write_config_dword(dev, l1ss + PCI_L1SS_CTL1, ctl1);
-	if (l1_2_enable)
-		pci_write_config_dword(dev, l1ss + PCI_L1SS_CTL1,
-				       ctl1 | l1_2_enable);
-}
-
 /* Calculate L1.2 PM substate timing parameters */
 static void aspm_calc_l1ss_info(struct pcie_link_state *link,
 				u32 parent_l1ss_cap, u32 child_l1ss_cap)
@@ -504,6 +479,7 @@ static void aspm_calc_l1ss_info(struct pcie_link_state *link,
 	u32 t_common_mode, t_power_on, l1_2_threshold, scale, value;
 	u32 ctl1 = 0, ctl2 = 0;
 	u32 pctl1, pctl2, cctl1, cctl2;
+	u32 pl1_2_enables, cl1_2_enables;
 
 	if (!(link->aspm_support & ASPM_STATE_L1_2_MASK))
 		return;
@@ -552,21 +528,39 @@ static void aspm_calc_l1ss_info(struct pcie_link_state *link,
 	    ctl2 == pctl2 && ctl2 == cctl2)
 		return;
 
-	pctl1 &= ~(PCI_L1SS_CTL1_CM_RESTORE_TIME |
-		   PCI_L1SS_CTL1_LTR_L12_TH_VALUE |
-		   PCI_L1SS_CTL1_LTR_L12_TH_SCALE);
-	pctl1 |= (ctl1 & (PCI_L1SS_CTL1_CM_RESTORE_TIME |
-			  PCI_L1SS_CTL1_LTR_L12_TH_VALUE |
-			  PCI_L1SS_CTL1_LTR_L12_TH_SCALE));
-	aspm_program_l1ss(parent, pctl1, ctl2);
-
-	cctl1 &= ~(PCI_L1SS_CTL1_CM_RESTORE_TIME |
-		   PCI_L1SS_CTL1_LTR_L12_TH_VALUE |
-		   PCI_L1SS_CTL1_LTR_L12_TH_SCALE);
-	cctl1 |= (ctl1 & (PCI_L1SS_CTL1_CM_RESTORE_TIME |
-			  PCI_L1SS_CTL1_LTR_L12_TH_VALUE |
-			  PCI_L1SS_CTL1_LTR_L12_TH_SCALE));
-	aspm_program_l1ss(child, cctl1, ctl2);
+	/* Disable L1.2 while updating.  See PCIe r5.0, sec 5.5.4, 7.8.3.3 */
+	pl1_2_enables = pctl1 & PCI_L1SS_CTL1_L1_2_MASK;
+	cl1_2_enables = cctl1 & PCI_L1SS_CTL1_L1_2_MASK;
+
+	if (pl1_2_enables || cl1_2_enables) {
+		pci_clear_and_set_dword(child, child->l1ss + PCI_L1SS_CTL1,
+					PCI_L1SS_CTL1_L1_2_MASK, 0);
+		pci_clear_and_set_dword(parent, parent->l1ss + PCI_L1SS_CTL1,
+					PCI_L1SS_CTL1_L1_2_MASK, 0);
+	}
+
+	/* Program T_POWER_ON times in both ports */
+	pci_write_config_dword(parent, parent->l1ss + PCI_L1SS_CTL2, ctl2);
+	pci_write_config_dword(child, child->l1ss + PCI_L1SS_CTL2, ctl2);
+
+	/* Program Common_Mode_Restore_Time in upstream device */
+	pci_clear_and_set_dword(parent, parent->l1ss + PCI_L1SS_CTL1,
+				PCI_L1SS_CTL1_CM_RESTORE_TIME, ctl1);
+
+	/* Program LTR_L1.2_THRESHOLD time in both ports */
+	pci_clear_and_set_dword(parent,	parent->l1ss + PCI_L1SS_CTL1,
+				PCI_L1SS_CTL1_LTR_L12_TH_VALUE |
+				PCI_L1SS_CTL1_LTR_L12_TH_SCALE, ctl1);
+	pci_clear_and_set_dword(child, child->l1ss + PCI_L1SS_CTL1,
+				PCI_L1SS_CTL1_LTR_L12_TH_VALUE |
+				PCI_L1SS_CTL1_LTR_L12_TH_SCALE, ctl1);
+
+	if (pl1_2_enables || cl1_2_enables) {
+		pci_clear_and_set_dword(parent, parent->l1ss + PCI_L1SS_CTL1, 0,
+					pl1_2_enables);
+		pci_clear_and_set_dword(child, child->l1ss + PCI_L1SS_CTL1, 0,
+					cl1_2_enables);
+	}
 }
 
 static void aspm_l1ss_init(struct pcie_link_state *link)