linux-kernel - [PATCH] PCI: Fix up L1SS capability for Intel Apollolake PCIe bridge

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Date:   Thu, 15 Dec 2022 11:48:57 +0800
From:   Ron Lee <ron.lee.intel@...il.com>
To:     bhelgaas@...gle.com
Cc:     linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org,
        lmajczak@...gle.com, rajatja@...gle.com,
        Ron Lee <ron.lee@...el.com>
Subject: [PATCH] PCI: Fix up L1SS capability for Intel Apollolake PCIe bridge

On Google Coral and Reef family chromebooks, the PCIe bridge lost its
L1 PM Substates capability after resumed from D3cold, and identify that
the pointer to the this capability and capapability header are missing
from the capability list.

....
Capabilities: [150 v0] Null
Capabilities: [200 v1] L1 PM Substates
        L1SubCap: PCI-PM_L1.2+ PCI-PM_L1.1+ ASPM_L1.2+ ASPM_L1.1+ ...
                  PortCommonModeRestoreTime=40us PortTPowerOnTime=10us
        L1SubCtl1: PCI-PM_L1.2+ PCI-PM_L1.1+ ASPM_L1.2+ ASPM_L1.1+
                   T_CommonMode=40us LTR1.2_Threshold=98304ns
        L1SubCtl2: T_PwrOn=60us
...

This patch fix up the header and the pointer to the L1SS capability
after resuming from D3Cold.

Signed-off-by: Ron Lee <ron.lee@...el.com>
---
 drivers/pci/quirks.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index 285acc4aaccc..e538f6d066f7 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -5992,3 +5992,18 @@ DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x9a2d, dpc_log_size);
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x9a2f, dpc_log_size);
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x9a31, dpc_log_size);
 #endif
+
+static void chromeos_fixup_apl_bridge_l1ss_capability(struct pci_dev *pdev)
+{
+	if (!dmi_match(DMI_SYS_VENDOR, "Google") ||
+		(!dmi_match(DMI_PRODUCT_FAMILY, "Google_Coral") &&
+		 !dmi_match(DMI_PRODUCT_FAMILY, "Google_Reef")))
+		return;
+
+	pci_info(pdev, "Fix up L1SS Capability\n");
+	/* Fix up the L1SS Capability Header*/
+	pci_write_config_dword(pdev, pdev->l1ss, (0x220 << 20) | (1 << 16) | (PCI_EXT_CAP_ID_L1SS));
+	/* Fix up the pointer to L1SS Capability*/
+	pci_write_config_dword(pdev, 0x150, pdev->l1ss << 20);
+}
+DECLARE_PCI_FIXUP_RESUME(PCI_VENDOR_ID_INTEL, 0x5ad6, chromeos_fixup_apl_bridge_l1ss_capability);
-- 
2.17.1