[PATCH 5.15.y 1/2] PCI: j721e: Enable ACSPCIE Refclk if "ti,syscon-acspcie-proxy-ctrl" exists

[Sasha Levin <sashal@kernel.org>]

From: Siddharth Vadapalli <s-vadapalli@ti.com>

[ Upstream commit 82c4be4168e26a5593aaa1002b5678128a638824 ]

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.

Add support to enable the ACSPCIE reference clock output using the optional
device-tree property "ti,syscon-acspcie-proxy-ctrl".

Link: https://lore.kernel.org/linux-pci/20240829105316.1483684-3-s-vadapalli@ti.com
Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Stable-dep-of: f842d3313ba1 ("PCI: j721e: Fix programming sequence of "strap" settings")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/pci/controller/cadence/pci-j721e.c | 39 +++++++++++++++++++++-
 1 file changed, 38 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/controller/cadence/pci-j721e.c b/drivers/pci/controller/cadence/pci-j721e.c
index 918e11082e6a7..b692dc5e3b99e 100644
--- a/drivers/pci/controller/cadence/pci-j721e.c
+++ b/drivers/pci/controller/cadence/pci-j721e.c
@@ -46,6 +46,7 @@ enum link_status {
 #define LANE_COUNT_MASK			BIT(8)
 #define LANE_COUNT(n)			((n) << 8)
 
+#define ACSPCIE_PAD_DISABLE_MASK	GENMASK(1, 0)
 #define GENERATION_SEL_MASK		GENMASK(1, 0)
 
 #define MAX_LANES			2
@@ -218,6 +219,36 @@ static int j721e_pcie_set_lane_count(struct j721e_pcie *pcie,
 	return ret;
 }
 
+static int j721e_enable_acspcie_refclk(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_DISABLE_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) {
+		dev_err(dev,
+			"ti,syscon-acspcie-proxy-ctrl has invalid arguments\n");
+		return ret;
+	}
+
+	/* Clear PAD IO disable bits to enable refclk output */
+	val = ~(args.args[0]);
+	ret = regmap_update_bits(syscon, 0, mask, val);
+	if (ret) {
+		dev_err(dev, "failed to enable ACSPCIE refclk: %d\n", ret);
+		return ret;
+	}
+
+	return 0;
+}
+
 static int j721e_pcie_ctrl_init(struct j721e_pcie *pcie)
 {
 	struct device *dev = pcie->dev;
@@ -257,7 +288,13 @@ static int j721e_pcie_ctrl_init(struct j721e_pcie *pcie)
 		return ret;
 	}
 
-	return 0;
+	/* Enable ACSPCIE refclk output if the optional property exists */
+	syscon = syscon_regmap_lookup_by_phandle_optional(node,
+						"ti,syscon-acspcie-proxy-ctrl");
+	if (!syscon)
+		return 0;
+
+	return j721e_enable_acspcie_refclk(pcie, syscon);
 }
 
 static int cdns_ti_pcie_config_read(struct pci_bus *bus, unsigned int devfn,
-- 
2.51.0