linux-kernel - [PATCH v2 2/3] PCI/ASPM: Use capability to override ASPM via sysfs

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Date:   Thu, 21 Oct 2021 11:51:58 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     bhelgaas@...gle.com
Cc:     hkallweit1@...il.com, anthony.wong@...onical.com,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
        Kai-Heng Feng <kai.heng.feng@...onical.com>,
        Logan Gunthorpe <logang@...tatee.com>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Vidya Sagar <vidyas@...dia.com>
Subject: [PATCH v2 2/3] PCI/ASPM: Use capability to override ASPM via sysfs

If we are to use sysfs to change ASPM settings, we may want to override
the default ASPM policy.

So use ASPM capability, instead of default policy, to be able to use all
possible ASPM states.

Upon power management change, pcie_aspm_pm_state_change() always
re-apply the state from global ASPM policy, so also introduce a new flag
to make the sysfs change persistent.

Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
---
v2:
 - Add flag to make ASPM change persistent

 drivers/pci/pcie/aspm.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 30b1bc899026..1560859ab056 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -60,6 +60,8 @@ struct pcie_link_state {
 	u32 aspm_default:7;		/* Default ASPM state by BIOS */
 	u32 aspm_disable:7;		/* Disabled ASPM state */
 
+	bool aspm_ignore_policy;	/* Ignore ASPM policy after sysfs overwrite */
+
 	/* Clock PM state */
 	u32 clkpm_capable:1;		/* Clock PM capable? */
 	u32 clkpm_enabled:1;		/* Current Clock PM state */
@@ -796,7 +798,8 @@ static void pcie_config_aspm_link(struct pcie_link_state *link, u32 state)
 static void pcie_config_aspm_path(struct pcie_link_state *link)
 {
 	while (link) {
-		pcie_config_aspm_link(link, policy_to_aspm_state(link));
+		pcie_config_aspm_link(link, link->aspm_ignore_policy ?
+				      link->aspm_capable : policy_to_aspm_state(link));
 		link = link->parent;
 	}
 }
@@ -1238,8 +1241,8 @@ static ssize_t aspm_attr_store_common(struct device *dev,
 
 		link->aspm_disable |= state;
 	}
-
-	pcie_config_aspm_link(link, policy_to_aspm_state(link));
+	pcie_config_aspm_link(link, link->aspm_capable);
+	link->aspm_ignore_policy = true;
 
 	mutex_unlock(&aspm_lock);
 	up_read(&pci_bus_sem);
-- 
2.32.0