linux-kernel - [PATCH V4 1/2] PCI/ASPM: Refactor ASPM L1SS control register programming

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Date:   Tue, 13 Sep 2022 18:48:21 +0530
From:   Vidya Sagar <vidyas@...dia.com>
To:     <bhelgaas@...gle.com>, <lorenzo.pieralisi@....com>,
        <refactormyself@...il.com>, <kw@...ux.com>, <rajatja@...gle.com>,
        <kenny@...ix.com>, <kai.heng.feng@...onical.com>,
        <abhsahu@...dia.com>, <sagupta@...dia.com>
CC:     <treding@...dia.com>, <jonathanh@...dia.com>,
        <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <kthota@...dia.com>, <mmaddireddy@...dia.com>, <vidyas@...dia.com>,
        <sagar.tv@...il.com>
Subject: [PATCH V4 1/2] PCI/ASPM: Refactor ASPM L1SS control register programming

Refactor the code to extract the command code out to program
Control Registers-1 & 2 of L1 Sub-States capability to a new function
aspm_program_l1ss() and call it for both parent and child devices.

Signed-off-by: Vidya Sagar <vidyas@...dia.com>
---
V4:
* New patch in this series

 drivers/pci/pcie/aspm.c | 63 +++++++++++++++++++----------------------
 1 file changed, 29 insertions(+), 34 deletions(-)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index a8aec190986c..ecbe3af4188d 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -455,6 +455,31 @@ 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)
@@ -464,7 +489,6 @@ 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;
@@ -513,39 +537,10 @@ static void aspm_calc_l1ss_info(struct pcie_link_state *link,
 	    ctl2 == pctl2 && ctl2 == cctl2)
 		return;
 
-	/* 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);
-	}
+	aspm_program_l1ss(parent,
+			  ctl1 | (pctl1 & PCI_L1SS_CTL1_L1_2_MASK), ctl2);
+	aspm_program_l1ss(child,
+			  ctl1 | (cctl1 & PCI_L1SS_CTL1_L1_2_MASK), ctl2);
 }
 
 static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
-- 
2.17.1