linux-kernel - [PATCH V2] PCI/ASPM: Update saved buffers with latest ASPM

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Message-ID: <20240103103501.2428197-1-vidyas@nvidia.com>
Date: Wed, 3 Jan 2024 16:05:01 +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 V2] PCI/ASPM: Update saved buffers with latest ASPM

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.

Update 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>
---
V2:
* Rebased on top of the tree code
* Addressed Bjorn's review comments

 drivers/pci/pcie/aspm.c | 26 +++++++++++++++++++++++++-
 1 file changed, 25 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 67b13f26ba7c..d247cabb5e4c 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -138,16 +138,36 @@ static int policy_to_clkpm_state(struct pcie_link_state *link)
 	return 0;
 }
 
+static 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++]);
+}
+
 static void pcie_set_clkpm_nocheck(struct pcie_link_state *link, int enable)
 {
 	struct pci_dev *child;
 	struct pci_bus *linkbus = link->pdev->subordinate;
 	u32 val = enable ? PCI_EXP_LNKCTL_CLKREQ_EN : 0;
 
-	list_for_each_entry(child, &linkbus->devices, bus_list)
+	list_for_each_entry(child, &linkbus->devices, bus_list) {
 		pcie_capability_clear_and_set_word(child, PCI_EXP_LNKCTL,
 						   PCI_EXP_LNKCTL_CLKREQ_EN,
 						   val);
+		pci_save_aspm_state(child);
+	}
 	link->clkpm_enabled = !!enable;
 }
 
@@ -767,6 +787,10 @@ 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_state(parent);
 }
 
 static void pcie_config_aspm_path(struct pcie_link_state *link)
-- 
2.25.1