linux-kernel - [RFC PATCH v5 3/4] PCI/ASPM: Remove struct pcie_link

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Message-Id: <20211119193732.12343-4-refactormyself@gmail.com>
Date:   Fri, 19 Nov 2021 20:37:31 +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, hch@....de
Subject: [RFC PATCH v5 3/4] 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 within pcie_aspm_check_latency() to validate actual
latencies. Thus, it is possible to avoid caching these values.

 - remove `acceptable` from struct pcie_link_state
 - calculate the acceptable latency for individual device directly
 - remove the calculations done within pcie_aspm_cap_init()

Signed-off-by: Saheed O. Bolarinwa <refactormyself@...il.com>
---
 drivers/pci/pcie/aspm.c | 28 +++++++++-------------------
 1 file changed, 9 insertions(+), 19 deletions(-)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 1b8933e0afb2..a8821fe1ffe7 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 +383,8 @@ static void encode_l12_threshold(u32 threshold_us, u32 *scale, u32 *value)
 
 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;
+	u32 l1_switch_latency = 0;
 	struct aspm_latency latency_up, latency_dw;
 	struct aspm_latency *acceptable;
 	struct pcie_link_state *link;
@@ -400,7 +395,13 @@ static void pcie_aspm_check_latency(struct pci_dev *endpoint)
 		return;
 
 	link = endpoint->bus->self->link_state;
-	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) {
 		struct pci_dev *dev = pci_function_0(
@@ -669,22 +670,11 @@ 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