[PATCH RFC 2/4] clk: qcom: Add generic clkref_en support

[Qiang Yu <qiang.yu@oss.qualcomm.com>]

Before XO refclk is distributed to PCIe/USB/eDP PHYs, it passes through
a QREF block. QREF is powered by dedicated LDO rails, and the clkref_en
register controls whether refclk is gated through to the PHY side.

These clkref controls are different from typical GCC branch clocks:
- only a single enable bit is present, without branch-style config bits
- regulators must be voted before enable and unvoted after disable

Model this as a dedicated clk_ref clock type with custom clk_ops instead
of reusing struct clk_branch semantics.

Also provide a common registration/probe API so the same clkref model
can be reused regardless of where clkref_en registers are placed, e.g.
TCSR on glymur and TLMM on SM8750.

Signed-off-by: Qiang Yu <qiang.yu@oss.qualcomm.com>
---
 drivers/clk/qcom/Makefile  |   1 +
 drivers/clk/qcom/clk-ref.c | 202 +++++++++++++++++++++++++++++++++++++++++++++
 include/linux/clk/qcom.h   |  69 ++++++++++++++++
 3 files changed, 272 insertions(+)

diff --git a/drivers/clk/qcom/Makefile b/drivers/clk/qcom/Makefile
index b818fd5af8bfb85a51ee90fdc3baa93af30dc39a..c5effc18efd80dd6c25a5398d723cec0f66fe0e6 100644
--- a/drivers/clk/qcom/Makefile
+++ b/drivers/clk/qcom/Makefile
@@ -8,6 +8,7 @@ clk-qcom-y += clk-pll.o
 clk-qcom-y += clk-rcg.o
 clk-qcom-y += clk-rcg2.o
 clk-qcom-y += clk-branch.o
+clk-qcom-y += clk-ref.o
 clk-qcom-y += clk-regmap-divider.o
 clk-qcom-y += clk-regmap-mux.o
 clk-qcom-y += clk-regmap-mux-div.o
diff --git a/drivers/clk/qcom/clk-ref.c b/drivers/clk/qcom/clk-ref.c
new file mode 100644
index 0000000000000000000000000000000000000000..ea2ed03460f28c6dae089e19cc07a5697b9f3d35
--- /dev/null
+++ b/drivers/clk/qcom/clk-ref.c
@@ -0,0 +1,202 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2026, Qualcomm Technologies, Inc. and/or its subsidiaries.
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/clk/qcom.h>
+#include <linux/delay.h>
+#include <linux/err.h>
+#include <linux/export.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
+#include <linux/slab.h>
+
+#define QCOM_CLK_REF_EN_MASK BIT(0)
+
+struct qcom_clk_ref_provider {
+	struct qcom_clk_ref *refs;
+	size_t num_refs;
+};
+
+static inline struct qcom_clk_ref *to_qcom_clk_ref(struct clk_hw *hw)
+{
+	return container_of(hw, struct qcom_clk_ref, hw);
+}
+
+static const struct clk_parent_data qcom_clk_ref_parent_data = {
+	.index = 0,
+};
+
+static int qcom_clk_ref_prepare(struct clk_hw *hw)
+{
+	struct qcom_clk_ref *rclk = to_qcom_clk_ref(hw);
+	int ret;
+
+	if (!rclk->desc.num_regulators)
+		return 0;
+
+	ret = regulator_bulk_enable(rclk->desc.num_regulators, rclk->regulators);
+	if (ret)
+		pr_err("Failed to enable regulators for %s: %d\n",
+		       clk_hw_get_name(hw), ret);
+
+	return ret;
+}
+
+static void qcom_clk_ref_unprepare(struct clk_hw *hw)
+{
+	struct qcom_clk_ref *rclk = to_qcom_clk_ref(hw);
+
+	if (rclk->desc.num_regulators)
+		regulator_bulk_disable(rclk->desc.num_regulators, rclk->regulators);
+}
+
+static int qcom_clk_ref_enable(struct clk_hw *hw)
+{
+	struct qcom_clk_ref *rclk = to_qcom_clk_ref(hw);
+	int ret;
+
+	ret = regmap_update_bits(rclk->regmap, rclk->desc.offset, QCOM_CLK_REF_EN_MASK,
+				 QCOM_CLK_REF_EN_MASK);
+	if (ret)
+		return ret;
+
+	udelay(10);
+
+	return 0;
+}
+
+static void qcom_clk_ref_disable(struct clk_hw *hw)
+{
+	struct qcom_clk_ref *rclk = to_qcom_clk_ref(hw);
+
+	regmap_update_bits(rclk->regmap, rclk->desc.offset, QCOM_CLK_REF_EN_MASK, 0);
+	udelay(10);
+}
+
+static int qcom_clk_ref_is_enabled(struct clk_hw *hw)
+{
+	struct qcom_clk_ref *rclk = to_qcom_clk_ref(hw);
+	u32 val;
+	int ret;
+
+	ret = regmap_read(rclk->regmap, rclk->desc.offset, &val);
+	if (ret)
+		return ret;
+
+	return !!(val & QCOM_CLK_REF_EN_MASK);
+}
+
+static const struct clk_ops qcom_clk_ref_ops = {
+	.prepare = qcom_clk_ref_prepare,
+	.unprepare = qcom_clk_ref_unprepare,
+	.enable = qcom_clk_ref_enable,
+	.disable = qcom_clk_ref_disable,
+	.is_enabled = qcom_clk_ref_is_enabled,
+};
+
+static int qcom_clk_ref_register(struct device *dev, struct regmap *regmap,
+				 struct qcom_clk_ref *clk_refs,
+				 const struct qcom_clk_ref_desc *descs,
+				 size_t num_clk_refs)
+{
+	const struct qcom_clk_ref_desc *desc;
+	struct qcom_clk_ref *clk_ref;
+	size_t clk_idx;
+	unsigned int i;
+	int ret;
+
+	for (clk_idx = 0; clk_idx < num_clk_refs; clk_idx++) {
+		clk_ref = &clk_refs[clk_idx];
+		desc = &descs[clk_idx];
+
+		if (!desc->name)
+			return -EINVAL;
+
+		clk_ref->regmap = regmap;
+		clk_ref->desc = *desc;
+
+		if (clk_ref->desc.num_regulators) {
+			clk_ref->regulators = devm_kcalloc(dev, clk_ref->desc.num_regulators,
+							   sizeof(*clk_ref->regulators),
+							   GFP_KERNEL);
+			if (!clk_ref->regulators)
+				return -ENOMEM;
+
+			for (i = 0; i < clk_ref->desc.num_regulators; i++)
+				clk_ref->regulators[i].supply =
+					clk_ref->desc.regulator_names[i];
+
+			ret = devm_regulator_bulk_get(dev, clk_ref->desc.num_regulators,
+						      clk_ref->regulators);
+			if (ret)
+				return dev_err_probe(dev, ret,
+						     "Failed to get regulators for %s\n",
+						     clk_ref->desc.name);
+		}
+
+		clk_ref->init_data.name = clk_ref->desc.name;
+		clk_ref->init_data.parent_data = &qcom_clk_ref_parent_data;
+		clk_ref->init_data.num_parents = 1;
+		clk_ref->init_data.ops = &qcom_clk_ref_ops;
+		clk_ref->hw.init = &clk_ref->init_data;
+
+		ret = devm_clk_hw_register(dev, &clk_ref->hw);
+		if (ret)
+			return ret;
+	}
+
+	return 0;
+}
+
+static struct clk_hw *qcom_clk_ref_provider_get(struct of_phandle_args *clkspec, void *data)
+{
+	struct qcom_clk_ref_provider *provider = data;
+	unsigned int idx = clkspec->args[0];
+
+	if (idx >= provider->num_refs)
+		return ERR_PTR(-EINVAL);
+
+	return &provider->refs[idx].hw;
+}
+
+int qcom_clk_ref_probe(struct platform_device *pdev,
+		       const struct regmap_config *config,
+		       const struct qcom_clk_ref_desc *descs,
+		       size_t num_clk_refs)
+{
+	struct qcom_clk_ref_provider *provider;
+	struct device *dev = &pdev->dev;
+	struct regmap *regmap;
+	void __iomem *base;
+	int ret;
+
+	base = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(base))
+		return PTR_ERR(base);
+
+	regmap = devm_regmap_init_mmio(dev, base, config);
+	if (IS_ERR(regmap))
+		return PTR_ERR(regmap);
+
+	provider = devm_kzalloc(dev, sizeof(*provider), GFP_KERNEL);
+	if (!provider)
+		return -ENOMEM;
+
+	provider->refs = devm_kcalloc(dev, num_clk_refs, sizeof(*provider->refs),
+				      GFP_KERNEL);
+	if (!provider->refs)
+		return -ENOMEM;
+
+	provider->num_refs = num_clk_refs;
+
+	ret = qcom_clk_ref_register(dev, regmap, provider->refs, descs,
+				    provider->num_refs);
+	if (ret)
+		return ret;
+
+	return devm_of_clk_add_hw_provider(dev, qcom_clk_ref_provider_get, provider);
+}
+EXPORT_SYMBOL_GPL(qcom_clk_ref_probe);
diff --git a/include/linux/clk/qcom.h b/include/linux/clk/qcom.h
new file mode 100644
index 0000000000000000000000000000000000000000..1066ef46ac21e9db1f3440faf81ba52afdf1faf2
--- /dev/null
+++ b/include/linux/clk/qcom.h
@@ -0,0 +1,69 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (c) 2026, Qualcomm Technologies, Inc. and/or its subsidiaries.
+ */
+
+#ifndef __LINUX_CLK_QCOM_H
+#define __LINUX_CLK_QCOM_H
+
+#include <linux/clk-provider.h>
+#include <linux/errno.h>
+#include <linux/kconfig.h>
+#include <linux/regmap.h>
+#include <linux/types.h>
+
+struct device;
+struct platform_device;
+struct regulator_bulk_data;
+
+/**
+ * struct qcom_clk_ref_desc - description of a simple XO reference gate
+ * @name: clock name
+ * @offset: register offset
+ * @regulator_names: optional per-clock regulator names
+ * @num_regulators: number of entries in @regulator_names
+ */
+struct qcom_clk_ref_desc {
+	const char *name;
+	u32 offset;
+	const char * const *regulator_names;
+	unsigned int num_regulators;
+};
+
+/**
+ * struct qcom_clk_ref - runtime state for a qcom reference gate
+ * @hw: clock hardware handle
+ * @init_data: clock init data
+ * @regmap: register map backing the gate register
+ * @desc: clock descriptor copied at registration
+ * @regulators: optional regulator handles
+ */
+struct qcom_clk_ref {
+	struct clk_hw hw;
+	struct clk_init_data init_data;
+	struct regmap *regmap;
+	struct qcom_clk_ref_desc desc;
+	struct regulator_bulk_data *regulators;
+};
+
+#if IS_ENABLED(CONFIG_COMMON_CLK_QCOM)
+
+int qcom_clk_ref_probe(struct platform_device *pdev,
+		       const struct regmap_config *config,
+		       const struct qcom_clk_ref_desc *descs,
+		       size_t num_clk_refs);
+
+#else
+
+static inline int
+qcom_clk_ref_probe(struct platform_device *pdev,
+		   const struct regmap_config *config,
+		   const struct qcom_clk_ref_desc *descs,
+		   size_t num_clk_refs)
+{
+	return -EOPNOTSUPP;
+}
+
+#endif
+
+#endif

-- 
2.34.1