clk: rockchip: introduce GRF gates

Some rockchip SoCs, namely the RK3576, have bits in a General Register
File (GRF) that act just like clock gates. The downstream vendor kernel
simply maps over the already mapped GRF range with a generic clock gate
driver. This solution isn't suitable for upstream, as a memory range
will be in use by multiple drivers at the same time, and it leaks
implementation details into the device tree.

Instead, implement this with a new clock branch type in the Rockchip
clock driver: GRF gates. Somewhat akin to MUXGRF, this clock branch
depends on the type of GRF, but functions like a gate instead.

Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
Link: https://lore.kernel.org/r/20250502-rk3576-sai-v3-3-376cef19dd7c@collabora.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

drivers/clk/rockchip/Makefile

@@ -14,6 +14,7 @@ clk-rockchip-y += clk-mmc-phase.o
 clk-rockchip-y += clk-muxgrf.o
 clk-rockchip-y += clk-ddr.o
 clk-rockchip-y += gate-link.o
+clk-rockchip-y += gate-grf.o
 clk-rockchip-$(CONFIG_RESET_CONTROLLER) += softrst.o
 
 obj-$(CONFIG_CLK_PX30)          += clk-px30.o

drivers/clk/rockchip/clk.c

@@ -509,7 +509,7 @@ void rockchip_clk_register_branches(struct rockchip_clk_provider *ctx,
 		clk = NULL;
 
 		/* for GRF-dependent branches, choose the right grf first */
-		if (list->branch_type == branch_muxgrf &&
+		if ((list->branch_type == branch_muxgrf || list->branch_type == branch_grf_gate) &&
 				list->grf_type != grf_type_sys) {
 			hash_for_each_possible(ctx->aux_grf_table, agrf, node, list->grf_type) {
 				if (agrf->type == list->grf_type) {
@@ -588,6 +588,13 @@ void rockchip_clk_register_branches(struct rockchip_clk_provider *ctx,
 				ctx->reg_base + list->gate_offset,
 				list->gate_shift, list->gate_flags, &ctx->lock);
 			break;
+		case branch_grf_gate:
+			flags |= CLK_SET_RATE_PARENT;
+			clk = rockchip_clk_register_gate_grf(list->name,
+				list->parent_names[0], flags, grf,
+				list->gate_offset, list->gate_shift,
+				list->gate_flags);
+			break;
 		case branch_composite:
 			clk = rockchip_clk_register_branch(list->name,
 				list->parent_names, list->num_parents,

drivers/clk/rockchip/clk.h

@@ -647,6 +647,11 @@ struct clk *rockchip_clk_register_muxgrf(const char *name,
 				int flags, struct regmap *grf, int reg,
 				int shift, int width, int mux_flags);
 
+struct clk *rockchip_clk_register_gate_grf(const char *name,
+				const char *parent_name, unsigned long flags,
+				struct regmap *regmap, unsigned int reg,
+				unsigned int shift, u8 gate_flags);
+
 #define PNAME(x) static const char *const x[] __initconst
 
 enum rockchip_clk_branch_type {
@@ -656,6 +661,7 @@ enum rockchip_clk_branch_type {
 	branch_divider,
 	branch_fraction_divider,
 	branch_gate,
+	branch_grf_gate,
 	branch_linked_gate,
 	branch_mmc,
 	branch_inverter,
@@ -985,6 +991,20 @@ struct rockchip_clk_branch {
 		.gate_flags	= gf,				\
 	}
 
+#define GATE_GRF(_id, cname, pname, f, o, b, gf, gt)		\
+	{							\
+		.id		= _id,				\
+		.branch_type	= branch_grf_gate,		\
+		.name		= cname,			\
+		.parent_names	= (const char *[]){ pname },	\
+		.num_parents	= 1,				\
+		.flags		= f,				\
+		.gate_offset	= o,				\
+		.gate_shift	= b,				\
+		.gate_flags	= gf,				\
+		.grf_type	= gt,				\
+	}
+
 #define GATE_LINK(_id, cname, pname, linkedclk, f, o, b, gf)	\
 	{							\
 		.id		= _id,				\

drivers/clk/rockchip/gate-grf.c

@@ -0,0 +1,105 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2025 Collabora Ltd.
+ * Author: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
+ *
+ * Certain clocks on Rockchip are "gated" behind an additional register bit
+ * write in a GRF register, such as the SAI MCLKs on RK3576. This code
+ * implements a clock driver for these types of gates, based on regmaps.
+ */
+
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>
+#include "clk.h"
+
+struct rockchip_gate_grf {
+	struct clk_hw		hw;
+	struct regmap		*regmap;
+	unsigned int		reg;
+	unsigned int		shift;
+	u8			flags;
+};
+
+#define to_gate_grf(_hw) container_of(_hw, struct rockchip_gate_grf, hw)
+
+static int rockchip_gate_grf_enable(struct clk_hw *hw)
+{
+	struct rockchip_gate_grf *gate = to_gate_grf(hw);
+	u32 val = !(gate->flags & CLK_GATE_SET_TO_DISABLE) ? BIT(gate->shift) : 0;
+	u32 hiword = ((gate->flags & CLK_GATE_HIWORD_MASK) ? 1 : 0) << (gate->shift + 16);
+	int ret;
+
+	ret = regmap_update_bits(gate->regmap, gate->reg,
+				 hiword | BIT(gate->shift), hiword | val);
+
+	return ret;
+}
+
+static void rockchip_gate_grf_disable(struct clk_hw *hw)
+{
+	struct rockchip_gate_grf *gate = to_gate_grf(hw);
+	u32 val = !(gate->flags & CLK_GATE_SET_TO_DISABLE) ? 0 : BIT(gate->shift);
+	u32 hiword = ((gate->flags & CLK_GATE_HIWORD_MASK) ? 1 : 0) << (gate->shift + 16);
+
+	regmap_update_bits(gate->regmap, gate->reg,
+			   hiword | BIT(gate->shift), hiword | val);
+}
+
+static int rockchip_gate_grf_is_enabled(struct clk_hw *hw)
+{
+	struct rockchip_gate_grf *gate = to_gate_grf(hw);
+	bool invert = !!(gate->flags & CLK_GATE_SET_TO_DISABLE);
+	int ret;
+
+	ret = regmap_test_bits(gate->regmap, gate->reg, BIT(gate->shift));
+	if (ret < 0)
+		ret = 0;
+
+	return invert ? 1 - ret : ret;
+
+}
+
+static const struct clk_ops rockchip_gate_grf_ops = {
+	.enable = rockchip_gate_grf_enable,
+	.disable = rockchip_gate_grf_disable,
+	.is_enabled = rockchip_gate_grf_is_enabled,
+};
+
+struct clk *rockchip_clk_register_gate_grf(const char *name,
+		const char *parent_name, unsigned long flags,
+		struct regmap *regmap, unsigned int reg, unsigned int shift,
+		u8 gate_flags)
+{
+	struct rockchip_gate_grf *gate;
+	struct clk_init_data init;
+	struct clk *clk;
+
+	if (IS_ERR(regmap)) {
+		pr_err("%s: regmap not available\n", __func__);
+		return ERR_PTR(-EOPNOTSUPP);
+	}
+
+	gate = kzalloc(sizeof(*gate), GFP_KERNEL);
+	if (!gate)
+		return ERR_PTR(-ENOMEM);
+
+	init.name = name;
+	init.flags = flags;
+	init.num_parents = parent_name ? 1 : 0;
+	init.parent_names = parent_name ? &parent_name : NULL;
+	init.ops = &rockchip_gate_grf_ops;
+
+	gate->hw.init = &init;
+	gate->regmap = regmap;
+	gate->reg = reg;
+	gate->shift = shift;
+	gate->flags = gate_flags;
+
+	clk = clk_register(NULL, &gate->hw);
+	if (IS_ERR(clk))
+		kfree(gate);
+
+	return clk;
+}