From 99c2279abfb228baa6b7ff3c3cf52bc57a216fd9 Mon Sep 17 00:00:00 2001
From: Neil Armstrong <narmstrong@baylibre.com>
Date: Fri, 2 Jul 2021 16:40:49 +0200
Subject: [PATCH] pci: add Extended PCI(e) capability offset get

Extend the PCIe API to find Extended Capabilities in the PCI Express
Extended Capabilities located in Configuration Space at offsets 256
or greater.

Note: the Root Complex Register Block is not supported

Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
---
 drivers/pcie/host/pcie.c    | 25 +++++++++++++++++++++++++
 include/drivers/pcie/pcie.h | 24 ++++++++++++++++++++++++
 2 files changed, 49 insertions(+)

diff --git a/drivers/pcie/host/pcie.c b/drivers/pcie/host/pcie.c
index acb73288759..62022a6b89c 100644
--- a/drivers/pcie/host/pcie.c
+++ b/drivers/pcie/host/pcie.c
@@ -71,6 +71,31 @@ uint32_t pcie_get_cap(pcie_bdf_t bdf, uint32_t cap_id)
 	return reg;
 }
 
+uint32_t pcie_get_ext_cap(pcie_bdf_t bdf, uint32_t cap_id)
+{
+	unsigned int reg = PCIE_CONF_EXT_CAPPTR; /* Start at end of the PCI configuration space */
+	uint32_t data;
+
+	while (reg) {
+		data = pcie_conf_read(bdf, reg);
+		if (!data || data == 0xffffffff) {
+			return 0;
+		}
+
+		if (PCIE_CONF_EXT_CAP_ID(data) == cap_id) {
+			break;
+		}
+
+		reg = PCIE_CONF_EXT_CAP_NEXT(data) >> 2;
+
+		if (reg < PCIE_CONF_EXT_CAPPTR) {
+			return 0;
+		}
+	}
+
+	return reg;
+}
+
 bool pcie_get_mbar(pcie_bdf_t bdf,
 		   unsigned int bar_index,
 		   struct pcie_mbar *mbar)
diff --git a/include/drivers/pcie/pcie.h b/include/drivers/pcie/pcie.h
index 327702af6f0..0a9e0bd6223 100644
--- a/include/drivers/pcie/pcie.h
+++ b/include/drivers/pcie/pcie.h
@@ -167,6 +167,15 @@ extern void pcie_irq_enable(pcie_bdf_t bdf, unsigned int irq);
  */
 extern uint32_t pcie_get_cap(pcie_bdf_t bdf, uint32_t cap_id);
 
+/**
+ * @brief Find an Extended PCI(e) capability in an endpoint's configuration space.
+ *
+ * @param bdf the PCI endpoint to examine
+ * @param cap_id the capability ID of interest
+ * @return the index of the configuration word, or 0 if no capability.
+ */
+extern uint32_t pcie_get_ext_cap(pcie_bdf_t bdf, uint32_t cap_id);
+
 /*
  * Configuration word 13 contains the head of the capabilities list.
  */
@@ -182,6 +191,21 @@ extern uint32_t pcie_get_cap(pcie_bdf_t bdf, uint32_t cap_id);
 #define PCIE_CONF_CAP_ID(w)		((w) & 0xFFU)
 #define PCIE_CONF_CAP_NEXT(w)		(((w) >> 10) & 0x3FU)
 
+/*
+ * The extended PCI Express capabilies lies at the end of the PCI configuration space
+ */
+
+#define PCIE_CONF_EXT_CAPPTR	64U
+
+/*
+ * The first word of every capability contains an extended capability identifier,
+ * and a link to the next capability (or 0) in the extended configuration space.
+ */
+
+#define PCIE_CONF_EXT_CAP_ID(w)		((w) & 0xFFFFU)
+#define PCIE_CONF_EXT_CAP_VER(w)	(((w) >> 16) & 0xFU)
+#define PCIE_CONF_EXT_CAP_NEXT(w)	(((w) >> 20) & 0xFFFU)
+
 /*
  * Configuration word 0 aligns directly with pcie_id_t.
  */