linux-kernel - [PATCH V1] PCI/ASPM: Update saved buffers with latest ASPM configuration

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Date:   Wed, 25 Jan 2023 19:08:30 +0530
From:   Vidya Sagar <vidyas@...dia.com>
To:     <bhelgaas@...gle.com>,
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        <rafael.j.wysocki@...el.com>, <kai.heng.feng@...onical.com>
CC:     <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <treding@...dia.com>, <jonathanh@...dia.com>, <kthota@...dia.com>,
        <mmaddireddy@...dia.com>, <vidyas@...dia.com>, <sagar.tv@...il.com>
Subject: [PATCH V1] PCI/ASPM: Update saved buffers with latest ASPM configuration

Many PCIe device drivers save the configuration state of their respective
devices during probe and restore the same when their 'slot_reset' hook
is called through PCIe Error Recovery System.
If the system has a change in ASPM policy after the driver's probe is
called and before error event occurred, 'slot_reset' hook restores the
PCIe configuration state to what it was at the time of probe but not with
what it was just before the occurrence of the error event.
This effectively leads to a mismatch in the ASPM configuration between
the device and its upstream parent device.
This patch addresses that issue by updating the saved configuration state
of the device with the latest info whenever there is a change w.r.t ASPM
policy.

Signed-off-by: Vidya Sagar <vidyas@...dia.com>
---
 drivers/pci/pci.h       |  4 ++++
 drivers/pci/pcie/aspm.c | 40 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+)

diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 9ed3b5550043..f4a91d4fe96d 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -566,12 +566,16 @@ bool pcie_wait_for_link(struct pci_dev *pdev, bool active);
 void pcie_aspm_init_link_state(struct pci_dev *pdev);
 void pcie_aspm_exit_link_state(struct pci_dev *pdev);
 void pcie_aspm_powersave_config_link(struct pci_dev *pdev);
+void pci_save_aspm_state(struct pci_dev *dev);
+void pci_restore_aspm_state(struct pci_dev *dev);
 void pci_save_aspm_l1ss_state(struct pci_dev *dev);
 void pci_restore_aspm_l1ss_state(struct pci_dev *dev);
 #else
 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_powersave_config_link(struct pci_dev *pdev) { }
+static inline void pci_save_aspm_state(struct pci_dev *dev) { }
+static inline void pci_restore_aspm_state(struct pci_dev *dev) { }
 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 53a1fa306e1e..f25e0440d36b 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -151,6 +151,7 @@ static void pcie_set_clkpm_nocheck(struct pcie_link_state *link, int enable)
 						   PCI_EXP_LNKCTL_CLKREQ_EN,
 						   val);
 	link->clkpm_enabled = !!enable;
+	pci_save_aspm_state(child);
 }
 
 static void pcie_set_clkpm(struct pcie_link_state *link, int enable)
@@ -757,6 +758,39 @@ static void pcie_config_aspm_l1ss(struct pcie_link_state *link, u32 state)
 				PCI_L1SS_CTL1_L1SS_MASK, val);
 }
 
+void pci_save_aspm_state(struct pci_dev *dev)
+{
+	int i = 0;
+	struct pci_cap_saved_state *save_state;
+	u16 *cap;
+
+	if (!pci_is_pcie(dev))
+		return;
+
+	save_state = pci_find_saved_cap(dev, PCI_CAP_ID_EXP);
+	if (!save_state)
+		return;
+
+	cap = (u16 *)&save_state->cap.data[0];
+	i++;
+	pcie_capability_read_word(dev, PCI_EXP_LNKCTL, &cap[i++]);
+}
+
+void pci_restore_aspm_state(struct pci_dev *dev)
+{
+	int i = 0;
+	struct pci_cap_saved_state *save_state;
+	u16 *cap;
+
+	save_state = pci_find_saved_cap(dev, PCI_CAP_ID_EXP);
+	if (!save_state)
+		return;
+
+	cap = (u16 *)&save_state->cap.data[0];
+	i++;
+	pcie_capability_write_word(dev, PCI_EXP_LNKCTL, cap[i++]);
+}
+
 void pci_save_aspm_l1ss_state(struct pci_dev *dev)
 {
 	struct pci_cap_saved_state *save_state;
@@ -849,6 +883,12 @@ static void pcie_config_aspm_link(struct pcie_link_state *link, u32 state)
 		pcie_config_aspm_dev(parent, upstream);
 
 	link->aspm_enabled = state;
+
+	/* Update latest ASPM configuration in saved context */
+	pci_save_aspm_state(link->downstream);
+	pci_save_aspm_l1ss_state(link->downstream);
+	pci_save_aspm_state(parent);
+	pci_save_aspm_l1ss_state(parent);
 }
 
 static void pcie_config_aspm_path(struct pcie_link_state *link)
-- 
2.17.1