linux-kernel - [PATCH 1/2] PCI/ASPM: Disable ASPM until its LTR and L1ss state is restored

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Date:   Tue, 12 Jan 2021 04:02:04 +0000
From:   Victor Ding <victording@...gle.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>,
        Adrian Hunter <adrian.hunter@...el.com>
Cc:     Ben Chuang <ben.chuang@...esyslogic.com.tw>,
        Bjorn Helgaas <helgaas@...nel.org>,
        linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-mmc@...r.kernel.org, Victor Ding <victording@...gle.com>,
        Alex Levin <levinale@...gle.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Kai-Heng Feng <kai.heng.feng@...onical.com>,
        "Saheed O. Bolarinwa" <refactormyself@...il.com>,
        Sean Paul <seanpaul@...omium.org>,
        Sukumar Ghorai <sukumar.ghorai@...el.com>,
        Yicong Yang <yangyicong@...ilicon.com>
Subject: [PATCH 1/2] PCI/ASPM: Disable ASPM until its LTR and L1ss state is restored

Right after powering up, the device may have ASPM enabled; however,
its LTR and/or L1ss controls may not be in the desired states; hence,
the device may enter L1.2 undesirably and cause resume performance
penalty. This is especially problematic if ASPM related control
registers are modified before a suspension.

Therefore, ASPM should disabled until its LTR and L1ss states are
fully restored.

Signed-off-by: Victor Ding <victording@...gle.com>
---

 drivers/pci/pci.c       | 11 +++++++++++
 drivers/pci/pci.h       |  2 ++
 drivers/pci/pcie/aspm.c |  2 +-
 3 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index eb323af34f1e..428de433f2e6 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1660,6 +1660,17 @@ void pci_restore_state(struct pci_dev *dev)
 	if (!dev->state_saved)
 		return;
 
+	/*
+	 * Right after powering up, the device may have ASPM enabled;
+	 * however, its LTR and/or L1ss controls may not be in the desired
+	 * states; as a result, the device may enter L1.2 undesirably and
+	 * cause resume performance penalty.
+	 * Therefore, ASPM is disabled until its LTR and L1ss states are
+	 * fully restored.
+	 * (enabling ASPM is part of pci_restore_pcie_state)
+	 */
+	pcie_config_aspm_dev(dev, 0);
+
 	/*
 	 * Restore max latencies (in the LTR capability) before enabling
 	 * LTR itself (in the PCIe capability).
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index e9ea5dfaa3e0..f774bd6d2555 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -564,6 +564,7 @@ void pcie_aspm_init_link_state(struct pci_dev *pdev);
 void pcie_aspm_exit_link_state(struct pci_dev *pdev);
 void pcie_aspm_pm_state_change(struct pci_dev *pdev);
 void pcie_aspm_powersave_config_link(struct pci_dev *pdev);
+void pcie_config_aspm_dev(struct pci_dev *pdev, u32 val);
 void pci_save_aspm_l1ss_state(struct pci_dev *dev);
 void pci_restore_aspm_l1ss_state(struct pci_dev *dev);
 #else
@@ -571,6 +572,7 @@ static inline void pcie_aspm_init_link_state(struct pci_dev *pdev) { }
 static inline void pcie_aspm_exit_link_state(struct pci_dev *pdev) { }
 static inline void pcie_aspm_pm_state_change(struct pci_dev *pdev) { }
 static inline void pcie_aspm_powersave_config_link(struct pci_dev *pdev) { }
+static inline void pcie_config_aspm_dev(struct pci_dev *pdev, u32 val) { }
 static inline void pci_save_aspm_l1ss_state(struct pci_dev *dev) { }
 static inline void pci_restore_aspm_l1ss_state(struct pci_dev *dev) { }
 #endif
diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index a08e7d6dc248..45535b4e1595 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -778,7 +778,7 @@ void pci_restore_aspm_l1ss_state(struct pci_dev *dev)
 	pci_write_config_dword(dev, aspm_l1ss + PCI_L1SS_CTL2, *cap++);
 }
 
-static void pcie_config_aspm_dev(struct pci_dev *pdev, u32 val)
+void pcie_config_aspm_dev(struct pci_dev *pdev, u32 val)
 {
 	pcie_capability_clear_and_set_word(pdev, PCI_EXP_LNKCTL,
 					   PCI_EXP_LNKCTL_ASPMC, val);
-- 
2.30.0.284.gd98b1dd5eaa7-goog