pci: pcie_dw_common: introduce pcie_dw_find_capability()

Add PCIe config space capability search function specific for
the host controller, which are bridges *to* PCI devices but
are not PCI devices themselves.

Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://lore.kernel.org/r/20241125-topic-pcie-controller-v1-1-45c20070dd53@linaro.org
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>

2 files changed, 44 insertions, 0 deletions

diff --git a/drivers/pci/pcie_dw_common.c b/drivers/pci/pcie_dw_common.c
index 0673e516c6f..78961271a8e 100644
--- a/drivers/pci/pcie_dw_common.c
+++ b/drivers/pci/pcie_dw_common.c
@@ -267,6 +267,48 @@ int pcie_dw_write_config(struct udevice *bus, pci_dev_t bdf,
 						 pcie->io.bus_start, pcie->io.size);
 }
 
+/*
+ * These interfaces resemble the pci_find_*capability() interfaces, but these
+ * are for configuring host controllers, which are bridges *to* PCI devices but
+ * are not PCI devices themselves.
+ */
+static u8 pcie_dw_find_next_cap(struct pcie_dw *pci, u8 cap_ptr, u8 cap)
+{
+	u8 cap_id, next_cap_ptr;
+	u32 val;
+	u16 reg;
+
+	if (!cap_ptr)
+		return 0;
+
+	val = readl(pci->dbi_base + (cap_ptr & ~0x3));
+	reg = pci_conv_32_to_size(val, cap_ptr, 2);
+	cap_id = (reg & 0x00ff);
+
+	if (cap_id > PCI_CAP_ID_MAX)
+		return 0;
+
+	if (cap_id == cap)
+		return cap_ptr;
+
+	next_cap_ptr = (reg & 0xff00) >> 8;
+	return pcie_dw_find_next_cap(pci, next_cap_ptr, cap);
+}
+
+u8 pcie_dw_find_capability(struct pcie_dw *pci, u8 cap)
+{
+	u8 next_cap_ptr;
+	u32 val;
+	u16 reg;
+
+	val = readl(pci->dbi_base + (PCI_CAPABILITY_LIST & ~0x3));
+	reg = pci_conv_32_to_size(val, PCI_CAPABILITY_LIST, 2);
+
+	next_cap_ptr = (reg & 0x00ff);
+
+	return pcie_dw_find_next_cap(pci, next_cap_ptr, cap);
+}
+
 /**
  * pcie_dw_setup_host() - Setup the PCIe controller for RC opertaion
  *
diff --git a/drivers/pci/pcie_dw_common.h b/drivers/pci/pcie_dw_common.h
index e0f7796f2a8..8cb99a12ea1 100644
--- a/drivers/pci/pcie_dw_common.h
+++ b/drivers/pci/pcie_dw_common.h
@@ -139,6 +139,8 @@ int pcie_dw_read_config(const struct udevice *bus, pci_dev_t bdf, uint offset, u
 int pcie_dw_write_config(struct udevice *bus, pci_dev_t bdf, uint offset, ulong value,
 			 enum pci_size_t size);
 
+u8 pcie_dw_find_capability(struct pcie_dw *pci, u8 cap);
+
 static inline void dw_pcie_dbi_write_enable(struct pcie_dw *pci, bool en)
 {
 	u32 val;