linux-kernel - [RFC PATCH v1 1/6] PCI/ASPM: Extract out L1SS

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Date:   Sat,  6 Nov 2021 18:53:48 +0100
From:   "Saheed O. Bolarinwa" <refactormyself@...il.com>
To:     helgaas@...nel.org
Cc:     "Saheed O. Bolarinwa" <refactormyself@...il.com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH v1 1/6] PCI/ASPM: Extract out L1SS_CAP calculations

Inside pcie_aspm_cap_init() the L1SS_CAP of both ends of the link is
calculated. The values are used to calculate link->aspm_support and
link->aspm_enabled. Isolating this calcution with simplify
pcie_aspm_cap_init().

Extract the calculations of L1SS_CAP on both ends into
aspm_calc_both_l1ss_caps().

Signed-off-by: Saheed O. Bolarinwa <refactormyself@...il.com>
---
 drivers/pci/pcie/aspm.c | 42 ++++++++++++++++++++++++-----------------
 1 file changed, 25 insertions(+), 17 deletions(-)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 013a47f587ce..057c6768fb7b 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -540,6 +540,30 @@ static void aspm_calc_l1ss_info(struct pcie_link_state *link,
 	}
 }
 
+static void aspm_calc_both_l1ss_caps(struct pcie_link_state *link,
+				    u32 *up_l1ss_cap, u32 *dwn_l1ss_cap)
+{
+	struct pci_dev *child = link->downstream, *parent = link->pdev;
+
+	pci_read_config_dword(parent, parent->l1ss + PCI_L1SS_CAP,
+			      up_l1ss_cap);
+	pci_read_config_dword(child, child->l1ss + PCI_L1SS_CAP,
+			      dwn_l1ss_cap);
+
+	if (!(*up_l1ss_cap & PCI_L1SS_CAP_L1_PM_SS))
+		*up_l1ss_cap = 0;
+	if (!(*dwn_l1ss_cap & PCI_L1SS_CAP_L1_PM_SS))
+		*dwn_l1ss_cap = 0;
+
+	/*
+	 * If we don't have LTR for the entire path from the Root Complex
+	 * to this device, we can't use ASPM L1.2 because it relies on the
+	 * LTR_L1.2_THRESHOLD.  See PCIe r4.0, secs 5.5.4, 6.18.
+	 */
+	if (!child->ltr_path)
+		*dwn_l1ss_cap &= ~PCI_L1SS_CAP_ASPM_L1_2;
+}
+
 static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
 {
 	struct pci_dev *child = link->downstream, *parent = link->pdev;
@@ -606,23 +630,7 @@ static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
 	link->latency_dw.l1 = calc_l1_latency(child_lnkcap);
 
 	/* Setup L1 substate */
-	pci_read_config_dword(parent, parent->l1ss + PCI_L1SS_CAP,
-			      &parent_l1ss_cap);
-	pci_read_config_dword(child, child->l1ss + PCI_L1SS_CAP,
-			      &child_l1ss_cap);
-
-	if (!(parent_l1ss_cap & PCI_L1SS_CAP_L1_PM_SS))
-		parent_l1ss_cap = 0;
-	if (!(child_l1ss_cap & PCI_L1SS_CAP_L1_PM_SS))
-		child_l1ss_cap = 0;
-
-	/*
-	 * If we don't have LTR for the entire path from the Root Complex
-	 * to this device, we can't use ASPM L1.2 because it relies on the
-	 * LTR_L1.2_THRESHOLD.  See PCIe r4.0, secs 5.5.4, 6.18.
-	 */
-	if (!child->ltr_path)
-		child_l1ss_cap &= ~PCI_L1SS_CAP_ASPM_L1_2;
+	aspm_calc_both_l1ss_caps(link, &parent_l1ss_cap, &child_l1ss_cap);
 
 	if (parent_l1ss_cap & child_l1ss_cap & PCI_L1SS_CAP_ASPM_L1_1)
 		link->aspm_support |= ASPM_STATE_L1_1;
-- 
2.20.1