linux-kernel - [RFC PATCH 2/3 v2] PCI/ASPM: Remove struct pcie_link

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Message-Id: <20210916084926.32614-3-refactormyself@gmail.com>
Date:   Thu, 16 Sep 2021 10:49:25 +0200
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,
        kw@...ux.com
Subject: [RFC PATCH 2/3 v2] PCI/ASPM: Remove struct pcie_link_state.acceptable

The acceptable latencies for each device on the bus are calculated within
pcie_aspm_cap_init() and cached in struct pcie_link_state.acceptable. They
are only used in pcie_aspm_check_latency() to validate actual latencies.
Thus, it is possible to avoid caching these values.

This patch:
  - removes `acceptable` from struct pcie_link_state
  - calculates the acceptable latency for each device directly
  - removes the calculations done within pcie_aspm_cap_init()

Signed-off-by: Saheed O. Bolarinwa <refactormyself@...il.com>
---
 drivers/pci/pcie/aspm.c | 27 ++++++++-------------------
 1 file changed, 8 insertions(+), 19 deletions(-)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 9e85dfc56657..0c0c055823f1 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -65,12 +65,6 @@ struct pcie_link_state {
 	u32 clkpm_enabled:1;		/* Current Clock PM state */
 	u32 clkpm_default:1;		/* Default Clock PM state by BIOS */
 	u32 clkpm_disable:1;		/* Clock PM disabled */
-
-	/*
-	 * Endpoint acceptable latencies. A pcie downstream port only
-	 * has one slot under it, so at most there are 8 functions.
-	 */
-	struct aspm_latency acceptable[8];
 };
 
 static int aspm_disabled, aspm_force;
@@ -389,7 +383,7 @@ static struct pci_dev *pci_function_0(struct pci_bus *linkbus)
 
 static void pcie_aspm_check_latency(struct pci_dev *endpoint)
 {
-	u32 latency, lnkcap_up, lnkcap_dw, l1_switch_latency = 0;
+	u32 reg32, latency, encoding, lnkcap_up, lnkcap_dw, l1_switch_latency = 0;
 	struct pci_dev *downstream;
 	struct aspm_latency latency_up, latency_dw;
 	struct aspm_latency *acceptable;
@@ -402,7 +396,13 @@ static void pcie_aspm_check_latency(struct pci_dev *endpoint)
 
 	link = endpoint->bus->self->link_state;
 	downstream = pci_function_0(link->pdev->subordinate);
-	acceptable = &link->acceptable[PCI_FUNC(endpoint->devfn)];
+	pcie_capability_read_dword(endpoint, PCI_EXP_DEVCAP, &reg32);
+	/* Calculate endpoint L0s acceptable latency */
+	encoding = (reg32 & PCI_EXP_DEVCAP_L0S) >> 6;
+	acceptable->l0s = calc_l0s_acceptable(encoding);
+	/* Calculate endpoint L1 acceptable latency */
+	encoding = (reg32 & PCI_EXP_DEVCAP_L1) >> 9;
+	acceptable->l1 = calc_l1_acceptable(encoding);
 
 	while (link) {
 		/* Read direction exit latencies */
@@ -664,22 +664,11 @@ static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
 
 	/* Get and check endpoint acceptable latencies */
 	list_for_each_entry(child, &linkbus->devices, bus_list) {
-		u32 reg32, encoding;
-		struct aspm_latency *acceptable =
-			&link->acceptable[PCI_FUNC(child->devfn)];
 
 		if (pci_pcie_type(child) != PCI_EXP_TYPE_ENDPOINT &&
 		    pci_pcie_type(child) != PCI_EXP_TYPE_LEG_END)
 			continue;
 
-		pcie_capability_read_dword(child, PCI_EXP_DEVCAP, &reg32);
-		/* Calculate endpoint L0s acceptable latency */
-		encoding = (reg32 & PCI_EXP_DEVCAP_L0S) >> 6;
-		acceptable->l0s = calc_l0s_acceptable(encoding);
-		/* Calculate endpoint L1 acceptable latency */
-		encoding = (reg32 & PCI_EXP_DEVCAP_L1) >> 9;
-		acceptable->l1 = calc_l1_acceptable(encoding);
-
 		pcie_aspm_check_latency(child);
 	}
 }
-- 
2.20.1