[PATCH 3/3] PCI: j721e: Add support for enabling ACSPCIE PAD IO Buffer output

[Siddharth Vadapalli]

The ACSPCIE module is capable of driving the reference clock required by
the PCIe Endpoint device. It is an alternative to on-board and external
reference clock generators. Enabling the output from the ACSPCIE module's
PAD IO Buffers requires clearing the "PAD IO disable" bits of the
ACSPCIE_PROXY_CTRL register in the CTRL_MMR register space.

Signed-off-by: Siddharth Vadapalli <s-vadapalli@xxxxxx>
---
 drivers/pci/controller/cadence/pci-j721e.c | 33 ++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/drivers/pci/controller/cadence/pci-j721e.c b/drivers/pci/controller/cadence/pci-j721e.c
index 85718246016b..2fa0eff68a8a 100644
--- a/drivers/pci/controller/cadence/pci-j721e.c
+++ b/drivers/pci/controller/cadence/pci-j721e.c
@@ -44,6 +44,7 @@ enum link_status {
 #define J721E_MODE_RC			BIT(7)
 #define LANE_COUNT(n)			((n) << 8)
 
+#define ACSPCIE_PAD_ENABLE_MASK		GENMASK(1, 0)
 #define GENERATION_SEL_MASK		GENMASK(1, 0)
 
 struct j721e_pcie {
@@ -220,6 +221,30 @@ static int j721e_pcie_set_lane_count(struct j721e_pcie *pcie,
 	return ret;
 }
 
+static int j721e_acspcie_pad_enable(struct j721e_pcie *pcie, struct regmap *syscon)
+{
+	struct device *dev = pcie->cdns_pcie->dev;
+	struct device_node *node = dev->of_node;
+	u32 mask = ACSPCIE_PAD_ENABLE_MASK;
+	struct of_phandle_args args;
+	u32 val;
+	int ret;
+
+	ret = of_parse_phandle_with_fixed_args(node, "ti,syscon-acspcie-proxy-ctrl",
+					       1, 0, &args);
+	if (!ret) {
+		/* PAD Enable Bits have to be cleared to in order to enable output */
+		val = ~(args.args[0]);
+		ret = regmap_update_bits(syscon, 0, mask, val);
+		if (ret)
+			dev_err(dev, "Enabling ACSPCIE PAD output failed: %d\n", ret);
+	} else {
+		dev_err(dev, "ti,syscon-acspcie-proxy-ctrl has invalid parameters\n");
+	}
+
+	return ret;
+}
+
 static int j721e_pcie_ctrl_init(struct j721e_pcie *pcie)
 {
 	struct device *dev = pcie->cdns_pcie->dev;
@@ -259,6 +284,14 @@ static int j721e_pcie_ctrl_init(struct j721e_pcie *pcie)
 		return ret;
 	}
 
+	/* Enable ACSPCIe PAD IO Buffers if the optional property exists */
+	syscon = syscon_regmap_lookup_by_phandle_optional(node, "ti,syscon-acspcie-proxy-ctrl");
+	if (syscon) {
+		ret = j721e_acspcie_pad_enable(pcie, syscon);
+		if (ret)
+			return ret;
+	}
+
 	return 0;
 }
 
-- 
2.40.1