PCI: iproc: Fix up corrupted PAXC root complex config registers

On certain versions of Broadcom PAXC based root complexes, certain
regions of the configuration space are corrupted. As a result, it
prevents the Linux PCIe stack from traversing the linked list of the
capability registers completely and therefore the root complex is
not advertised as "PCIe capable". This prevents the correct PCIe RID
from being parsed in the kernel PCIe stack. A correct RID is required
for mapping to a stream ID from the SMMU or the device ID from the
GICv3 ITS.

This patch fixes up the issue by manually populating the related
PCIe capabilities.

Signed-off-by: Ray Jui <rjui@broadcom.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Oza Pawandeep <poza@codeaurora.org>

drivers/pci/controller/pcie-iproc.c

@@ -85,6 +85,8 @@
 #define IMAP_VALID_SHIFT		0
 #define IMAP_VALID			BIT(IMAP_VALID_SHIFT)
 
+#define IPROC_PCI_PM_CAP		0x48
+#define IPROC_PCI_PM_CAP_MASK		0xffff
 #define IPROC_PCI_EXP_CAP		0xac
 
 #define IPROC_PCIE_REG_INVALID		0xffff
@@ -375,6 +377,17 @@ static const u16 iproc_pcie_reg_paxc_v2[] = {
 	[IPROC_PCIE_CFG_DATA]		= 0x1fc,
 };
 
+/*
+ * List of device IDs of controllers that have corrupted capability list that
+ * require SW fixup
+ */
+static const u16 iproc_pcie_corrupt_cap_did[] = {
+	0x16cd,
+	0x16f0,
+	0xd802,
+	0xd804
+};
+
 static inline struct iproc_pcie *iproc_data(struct pci_bus *bus)
 {
 	struct iproc_pcie *pcie = bus->sysdata;
@@ -495,6 +508,49 @@ static unsigned int iproc_pcie_cfg_retry(void __iomem *cfg_data_p)
 	return data;
 }
 
+static void iproc_pcie_fix_cap(struct iproc_pcie *pcie, int where, u32 *val)
+{
+	u32 i, dev_id;
+
+	switch (where & ~0x3) {
+	case PCI_VENDOR_ID:
+		dev_id = *val >> 16;
+
+		/*
+		 * Activate fixup for those controllers that have corrupted
+		 * capability list registers
+		 */
+		for (i = 0; i < ARRAY_SIZE(iproc_pcie_corrupt_cap_did); i++)
+			if (dev_id == iproc_pcie_corrupt_cap_did[i])
+				pcie->fix_paxc_cap = true;
+		break;
+
+	case IPROC_PCI_PM_CAP:
+		if (pcie->fix_paxc_cap) {
+			/* advertise PM, force next capability to PCIe */
+			*val &= ~IPROC_PCI_PM_CAP_MASK;
+			*val |= IPROC_PCI_EXP_CAP << 8 | PCI_CAP_ID_PM;
+		}
+		break;
+
+	case IPROC_PCI_EXP_CAP:
+		if (pcie->fix_paxc_cap) {
+			/* advertise root port, version 2, terminate here */
+			*val = (PCI_EXP_TYPE_ROOT_PORT << 4 | 2) << 16 |
+				PCI_CAP_ID_EXP;
+		}
+		break;
+
+	case IPROC_PCI_EXP_CAP + PCI_EXP_RTCTL:
+		/* Don't advertise CRS SV support */
+		*val &= ~(PCI_EXP_RTCAP_CRSVIS << 16);
+		break;
+
+	default:
+		break;
+	}
+}
+
 static int iproc_pcie_config_read(struct pci_bus *bus, unsigned int devfn,
 				  int where, int size, u32 *val)
 {
@@ -509,13 +565,10 @@ static int iproc_pcie_config_read(struct pci_bus *bus, unsigned int devfn,
 	/* root complex access */
 	if (busno == 0) {
 		ret = pci_generic_config_read32(bus, devfn, where, size, val);
-		if (ret != PCIBIOS_SUCCESSFUL)
-			return ret;
+		if (ret == PCIBIOS_SUCCESSFUL)
+			iproc_pcie_fix_cap(pcie, where, val);
 
-		/* Don't advertise CRS SV support */
-		if ((where & ~0x3) == IPROC_PCI_EXP_CAP + PCI_EXP_RTCTL)
-			*val &= ~(PCI_EXP_RTCAP_CRSVIS << 16);
-		return PCIBIOS_SUCCESSFUL;
+		return ret;
 	}
 
 	cfg_data_p = iproc_pcie_map_ep_cfg_reg(pcie, busno, slot, fn, where);

drivers/pci/controller/pcie-iproc.h

@@ -60,6 +60,8 @@ struct iproc_msi;
  * @ep_is_internal: indicates an internal emulated endpoint device is connected
  * @has_apb_err_disable: indicates the controller can be configured to prevent
  * unsupported request from being forwarded as an APB bus error
+ * @fix_paxc_cap: indicates the controller has corrupted capability list in its
+ * config space registers and requires SW based fixup
  *
  * @need_ob_cfg: indicates SW needs to configure the outbound mapping window
  * @ob: outbound mapping related parameters
@@ -85,6 +87,7 @@ struct iproc_pcie {
 	int (*map_irq)(const struct pci_dev *, u8, u8);
 	bool ep_is_internal;
 	bool has_apb_err_disable;
+	bool fix_paxc_cap;
 
 	bool need_ob_cfg;
 	struct iproc_pcie_ob ob;