clk: rockchip: implement linked gate clock support

Recent Rockchip SoCs have a new hardware block called Native Interface
Unit (NIU), which gates clocks to devices behind them. These clock
gates will only have a running output clock when all of the following
conditions are met:

1. the parent clock is enabled
2. the enable bit is set correctly
3. the linked clock is enabled

To handle them this code registers them as a normal gate type clock,
which takes care of condition 1 + 2. The linked clock is handled by
using runtime PM clocks. Handling it via runtime PM requires setting
up a struct device for each of these clocks with a driver attached
to use the correct runtime PM operations. Thus the complete handling
of these clocks has been moved into its own driver.

Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Link: https://lore.kernel.org/r/20241211165957.94922-5-sebastian.reichel@collabora.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>

drivers/clk/rockchip/Makefile

@@ -13,6 +13,7 @@ clk-rockchip-y += clk-inverter.o
 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-$(CONFIG_RESET_CONTROLLER) += softrst.o
 
 obj-$(CONFIG_CLK_PX30)          += clk-px30.o

drivers/clk/rockchip/clk-rk3588.c

@@ -12,25 +12,6 @@
 #include <dt-bindings/clock/rockchip,rk3588-cru.h>
 #include "clk.h"
 
-/*
- * Recent Rockchip SoCs have a new hardware block called Native Interface
- * Unit (NIU), which gates clocks to devices behind them. These effectively
- * need two parent clocks.
- *
- * Downstream enables the linked clock via runtime PM whenever the gate is
- * enabled. This implementation uses separate clock nodes for each of the
- * linked gate clocks, which leaks parts of the clock tree into DT.
- *
- * The GATE_LINK macro instead takes the second parent via 'linkname', but
- * ignores the information. Once the clock framework is ready to handle it, the
- * information should be passed on here. But since these clocks are required to
- * access multiple relevant IP blocks, such as PCIe or USB, we mark all linked
- * clocks critical until a better solution is available. This will waste some
- * power, but avoids leaking implementation details into DT or hanging the
- * system.
- */
-#define GATE_LINK(_id, cname, pname, linkedclk, f, o, b, gf) \
-	GATE(_id, cname, pname, f, o, b, gf)
 #define RK3588_LINKED_CLK		CLK_IS_CRITICAL
 
 
@@ -2513,8 +2494,8 @@ static int clk_rk3588_probe(struct platform_device *pdev)
 	struct device *dev = &pdev->dev;
 	struct device_node *np = dev->of_node;
 
-	rockchip_clk_register_branches(ctx, rk3588_clk_branches,
+	rockchip_clk_register_late_branches(dev, ctx, rk3588_clk_branches,
-				       ARRAY_SIZE(rk3588_clk_branches));
+					    ARRAY_SIZE(rk3588_clk_branches));
 
 	rockchip_clk_finalize(ctx);
 

drivers/clk/rockchip/clk.c

@@ -19,6 +19,7 @@
 #include <linux/clk-provider.h>
 #include <linux/io.h>
 #include <linux/mfd/syscon.h>
+#include <linux/platform_device.h>
 #include <linux/regmap.h>
 #include <linux/reboot.h>
 
@@ -468,6 +469,29 @@ unsigned long rockchip_clk_find_max_clk_id(struct rockchip_clk_branch *list,
 }
 EXPORT_SYMBOL_GPL(rockchip_clk_find_max_clk_id);
 
+static struct platform_device *rockchip_clk_register_gate_link(
+		struct device *parent_dev,
+		struct rockchip_clk_provider *ctx,
+		struct rockchip_clk_branch *clkbr)
+{
+	struct rockchip_gate_link_platdata gate_link_pdata = {
+		.ctx = ctx,
+		.clkbr = clkbr,
+	};
+
+	struct platform_device_info pdevinfo = {
+		.parent = parent_dev,
+		.name = "rockchip-gate-link-clk",
+		.id = clkbr->id,
+		.fwnode = dev_fwnode(parent_dev),
+		.of_node_reused = true,
+		.data = &gate_link_pdata,
+		.size_data = sizeof(gate_link_pdata),
+	};
+
+	return platform_device_register_full(&pdevinfo);
+}
+
 void rockchip_clk_register_branches(struct rockchip_clk_provider *ctx,
 				    struct rockchip_clk_branch *list,
 				    unsigned int nr_clk)
@@ -593,6 +617,9 @@ void rockchip_clk_register_branches(struct rockchip_clk_provider *ctx,
 				list->div_width, list->div_flags,
 				ctx->reg_base, &ctx->lock);
 			break;
+		case branch_linked_gate:
+			/* must be registered late, fall-through for error message */
+			break;
 		}
 
 		/* none of the cases above matched */
@@ -613,6 +640,31 @@ void rockchip_clk_register_branches(struct rockchip_clk_provider *ctx,
 }
 EXPORT_SYMBOL_GPL(rockchip_clk_register_branches);
 
+void rockchip_clk_register_late_branches(struct device *dev,
+					 struct rockchip_clk_provider *ctx,
+					 struct rockchip_clk_branch *list,
+					 unsigned int nr_clk)
+{
+	unsigned int idx;
+
+	for (idx = 0; idx < nr_clk; idx++, list++) {
+		struct platform_device *pdev = NULL;
+
+		switch (list->branch_type) {
+		case branch_linked_gate:
+			pdev = rockchip_clk_register_gate_link(dev, ctx, list);
+			break;
+		default:
+			dev_err(dev, "unknown clock type %d\n", list->branch_type);
+			break;
+		}
+
+		if (!pdev)
+			dev_err(dev, "failed to register device for clock %s\n", list->name);
+	}
+}
+EXPORT_SYMBOL_GPL(rockchip_clk_register_late_branches);
+
 void rockchip_clk_register_armclk(struct rockchip_clk_provider *ctx,
 				  unsigned int lookup_id,
 				  const char *name, const char *const *parent_names,

drivers/clk/rockchip/clk.h

@@ -570,6 +570,7 @@ enum rockchip_clk_branch_type {
 	branch_divider,
 	branch_fraction_divider,
 	branch_gate,
+	branch_linked_gate,
 	branch_mmc,
 	branch_inverter,
 	branch_factor,
@@ -597,6 +598,7 @@ struct rockchip_clk_branch {
 	int				gate_offset;
 	u8				gate_shift;
 	u8				gate_flags;
+	unsigned int			linked_clk_id;
 	struct rockchip_clk_branch	*child;
 };
 
@@ -895,6 +897,20 @@ struct rockchip_clk_branch {
 		.gate_flags	= gf,				\
 	}
 
+#define GATE_LINK(_id, cname, pname, linkedclk, f, o, b, gf)	\
+	{							\
+		.id		= _id,				\
+		.branch_type	= branch_linked_gate,		\
+		.name		= cname,			\
+		.parent_names	= (const char *[]){ pname },	\
+		.linked_clk_id	= linkedclk,			\
+		.num_parents	= 1,				\
+		.flags		= f,				\
+		.gate_offset	= o,				\
+		.gate_shift	= b,				\
+		.gate_flags	= gf,				\
+	}
+
 #define MMC(_id, cname, pname, offset, shift)			\
 	{							\
 		.id		= _id,				\
@@ -1034,6 +1050,11 @@ static inline void rockchip_clk_set_lookup(struct rockchip_clk_provider *ctx,
 	ctx->clk_data.clks[id] = clk;
 }
 
+struct rockchip_gate_link_platdata {
+	struct rockchip_clk_provider *ctx;
+	struct rockchip_clk_branch *clkbr;
+};
+
 struct rockchip_clk_provider *rockchip_clk_init(struct device_node *np,
 			void __iomem *base, unsigned long nr_clks);
 struct rockchip_clk_provider *rockchip_clk_init_early(struct device_node *np,
@@ -1046,6 +1067,10 @@ unsigned long rockchip_clk_find_max_clk_id(struct rockchip_clk_branch *list,
 void rockchip_clk_register_branches(struct rockchip_clk_provider *ctx,
 				    struct rockchip_clk_branch *list,
 				    unsigned int nr_clk);
+void rockchip_clk_register_late_branches(struct device *dev,
+					 struct rockchip_clk_provider *ctx,
+					 struct rockchip_clk_branch *list,
+					 unsigned int nr_clk);
 void rockchip_clk_register_plls(struct rockchip_clk_provider *ctx,
 				struct rockchip_pll_clock *pll_list,
 				unsigned int nr_pll, int grf_lock_offset);

drivers/clk/rockchip/gate-link.c

@@ -0,0 +1,85 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2024 Collabora Ltd.
+ * Author: Sebastian Reichel <sebastian.reichel@collabora.com>
+ */
+
+#include <linux/clk.h>
+#include <linux/platform_device.h>
+#include <linux/pm_clock.h>
+#include <linux/pm_runtime.h>
+#include <linux/property.h>
+#include "clk.h"
+
+static int rk_clk_gate_link_register(struct device *dev,
+				     struct rockchip_clk_provider *ctx,
+				     struct rockchip_clk_branch *clkbr)
+{
+	unsigned long flags = clkbr->flags | CLK_SET_RATE_PARENT;
+	struct clk *clk;
+
+	clk = clk_register_gate(dev, clkbr->name, clkbr->parent_names[0],
+				flags, ctx->reg_base + clkbr->gate_offset,
+				clkbr->gate_shift, clkbr->gate_flags,
+				&ctx->lock);
+
+	if (IS_ERR(clk))
+		return PTR_ERR(clk);
+
+	rockchip_clk_set_lookup(ctx, clk, clkbr->id);
+	return 0;
+}
+
+static int rk_clk_gate_link_probe(struct platform_device *pdev)
+{
+	struct rockchip_gate_link_platdata *pdata;
+	struct device *dev = &pdev->dev;
+	struct clk *linked_clk;
+	int ret;
+
+	pdata = dev_get_platdata(dev);
+	if (!pdata)
+		return dev_err_probe(dev, -ENODEV, "missing platform data");
+
+	ret = devm_pm_runtime_enable(dev);
+	if (ret)
+		return ret;
+
+	ret = devm_pm_clk_create(dev);
+	if (ret)
+		return ret;
+
+	linked_clk = rockchip_clk_get_lookup(pdata->ctx, pdata->clkbr->linked_clk_id);
+	ret = pm_clk_add_clk(dev, linked_clk);
+	if (ret)
+		return ret;
+
+	ret = rk_clk_gate_link_register(dev, pdata->ctx, pdata->clkbr);
+	if (ret)
+		goto err;
+
+	return 0;
+
+err:
+	pm_clk_remove_clk(dev, linked_clk);
+	return ret;
+}
+
+static const struct dev_pm_ops rk_clk_gate_link_pm_ops = {
+	SET_RUNTIME_PM_OPS(pm_clk_suspend, pm_clk_resume, NULL)
+};
+
+static struct platform_driver rk_clk_gate_link_driver = {
+	.probe		= rk_clk_gate_link_probe,
+	.driver		= {
+		.name	= "rockchip-gate-link-clk",
+		.pm = &rk_clk_gate_link_pm_ops,
+		.suppress_bind_attrs = true,
+	},
+};
+
+static int __init rk_clk_gate_link_drv_register(void)
+{
+	return platform_driver_register(&rk_clk_gate_link_driver);
+}
+core_initcall(rk_clk_gate_link_drv_register);