[PATCH] PCI/DPC: Quirk PIO log size for certain Intel PCIe root ports

[Mika Westerberg <mika.westerberg@linux.intel.com>]

There is a BIOS bug on Intel Tiger Lake and Alder Lake systems that
accidentally clears the root port PIO log size even though it should be 4.
Fix the affected root ports by forcing the log size to be 4 if it is set
to 0. The BIOS for the next generation CPUs should have this fixed.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=209943
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
---
 drivers/pci/pcie/dpc.c | 13 ++++++++-----
 drivers/pci/quirks.c   | 37 +++++++++++++++++++++++++++++++++++++
 2 files changed, 45 insertions(+), 5 deletions(-)

diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c
index 3e9afee02e8d..ab06c801a2c1 100644
--- a/drivers/pci/pcie/dpc.c
+++ b/drivers/pci/pcie/dpc.c
@@ -335,11 +335,14 @@ void pci_dpc_init(struct pci_dev *pdev)
 		return;
 
 	pdev->dpc_rp_extensions = true;
-	pdev->dpc_rp_log_size = (cap & PCI_EXP_DPC_RP_PIO_LOG_SIZE) >> 8;
-	if (pdev->dpc_rp_log_size < 4 || pdev->dpc_rp_log_size > 9) {
-		pci_err(pdev, "RP PIO log size %u is invalid\n",
-			pdev->dpc_rp_log_size);
-		pdev->dpc_rp_log_size = 0;
+	/* If not already set by the quirk in quirks.c */
+	if (!pdev->dpc_rp_log_size) {
+		pdev->dpc_rp_log_size = (cap & PCI_EXP_DPC_RP_PIO_LOG_SIZE) >> 8;
+		if (pdev->dpc_rp_log_size < 4 || pdev->dpc_rp_log_size > 9) {
+			pci_err(pdev, "RP PIO log size %u is invalid\n",
+				pdev->dpc_rp_log_size);
+			pdev->dpc_rp_log_size = 0;
+		}
 	}
 }
 
diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c
index 4944798e75b5..260d8b50f68d 100644
--- a/drivers/pci/quirks.c
+++ b/drivers/pci/quirks.c
@@ -5956,3 +5956,40 @@ DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x56b1, aspm_l1_acceptable_latency
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x56c0, aspm_l1_acceptable_latency);
 DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x56c1, aspm_l1_acceptable_latency);
 #endif
+
+#ifdef CONFIG_PCIE_DPC
+/*
+ * Intel Tiger Lake and Alder Lake BIOS has a bug that clears the DPC
+ * log size of the integrated Thunderbolt PCIe root ports so we quirk
+ * them here.
+ */
+static void dpc_log_size(struct pci_dev *dev)
+{
+	u16 dpc_cap, val;
+
+	dpc_cap = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_DPC);
+	if (!dpc_cap)
+		return;
+
+	pci_read_config_word(dev, dpc_cap + PCI_EXP_DPC_CAP, &val);
+	if (!(val & PCI_EXP_DPC_CAP_RP_EXT))
+		return;
+
+	if (!((val & PCI_EXP_DPC_RP_PIO_LOG_SIZE) >> 8)) {
+		pci_info(dev, "quirking RP PIO log size\n");
+		dev->dpc_rp_log_size = 4;
+	}
+}
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x461f, dpc_log_size);
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x462f, dpc_log_size);
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x463f, dpc_log_size);
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x466e, dpc_log_size);
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x9a23, dpc_log_size);
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x9a25, dpc_log_size);
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x9a27, dpc_log_size);
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x9a29, dpc_log_size);
+DECLARE_PCI_FIXUP_HEADER(PCI_VENDOR_ID_INTEL, 0x9a2b, dpc_log_size);
+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
-- 
2.35.1