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

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Message-ID: <20240715120936.1150314-4-s-vadapalli@ti.com>
Date: Mon, 15 Jul 2024 17:39:36 +0530
From: Siddharth Vadapalli <s-vadapalli@...com>
To: <lee@...nel.org>, <robh@...nel.org>, <krzk+dt@...nel.org>,
        <conor+dt@...nel.org>, <lpieralisi@...nel.org>, <kw@...ux.com>,
        <bhelgaas@...gle.com>, <vigneshr@...com>, <kishon@...nel.org>
CC: <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-pci@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>,
        <srk@...com>, <s-vadapalli@...com>
Subject: [PATCH 3/3] PCI: j721e: Add support for enabling ACSPCIE PAD IO Buffer output

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@...com>
---
 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