[RFC PATCH 05/11] clk: imx8mn: add divider driver

[Dario Binacchi]

The patch adds support for imx8mn divider clocks to be initialized
directly from the device tree. Currently all i.MX divider clocks are
initialized by legacy code with hardwired parameters.

So, let's start with this specific clock driver and hope that other
variants can be handled in the future, causing the legacy code to be
removed.

Signed-off-by: Dario Binacchi <dario.binacchi@xxxxxxxxxxxxxxxxxxxx>
---

 drivers/clk/imx/Makefile      |   1 +
 drivers/clk/imx/clk-divider.c | 235 ++++++++++++++++++++++++++++++++++
 2 files changed, 236 insertions(+)
 create mode 100644 drivers/clk/imx/clk-divider.c

diff --git a/drivers/clk/imx/Makefile b/drivers/clk/imx/Makefile
index 1cffc5bebbe1..0e4337f0a020 100644
--- a/drivers/clk/imx/Makefile
+++ b/drivers/clk/imx/Makefile
@@ -7,6 +7,7 @@ mxc-clk-objs += clk-composite-8m.o
 mxc-clk-objs += clk-composite-93.o
 mxc-clk-objs += clk-fracn-gppll.o
 mxc-clk-objs += clk-cpu.o
+mxc-clk-objs += clk-divider.o
 mxc-clk-objs += clk-divider-gate.o
 mxc-clk-objs += clk-fixup-div.o
 mxc-clk-objs += clk-fixup-mux.o
diff --git a/drivers/clk/imx/clk-divider.c b/drivers/clk/imx/clk-divider.c
new file mode 100644
index 000000000000..4617aa906de4
--- /dev/null
+++ b/drivers/clk/imx/clk-divider.c
@@ -0,0 +1,235 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (c) 2022 Amarula Solutions
+ *
+ * Dario Binacchi <dario.binacchi@xxxxxxxxxxxxxxxxxxxx>
+ */
+
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/regmap.h>
+
+#include "clk.h"
+
+#undef pr_fmt
+#define pr_fmt(fmt) "%s: " fmt, __func__
+
+#define to_clk_imx_divider(_hw) container_of(_hw, struct clk_imx_divider, hw)
+
+struct clk_imx_divider {
+	struct clk_hw hw;
+	struct imx_clk_reg reg;
+	u8 shift;
+	u8 width;
+};
+
+static int imx_clk_divider_write(const struct imx_clk_reg *reg, u32 val)
+{
+	int ret = 0;
+
+	if (reg->base) {
+		writel(val, reg->base + reg->offset);
+	} else if (reg->regmap) {
+		ret = regmap_write(reg->regmap, reg->offset, val);
+	} else {
+		pr_err("memory address not set\n");
+		ret = -EIO;
+	}
+
+	return ret;
+}
+
+static int imx_clk_divider_read(const struct imx_clk_reg *reg, u32 *val)
+{
+	int ret = 0;
+
+	if (reg->base) {
+		*val = readl(reg->base + reg->offset);
+	} else if (reg->regmap) {
+		ret = regmap_read(reg->regmap, reg->offset, val);
+	} else {
+		pr_err("memory address not set\n");
+		ret = -EIO;
+	}
+
+	return ret;
+}
+
+static unsigned long imx_clk_divider_recalc_rate(struct clk_hw *hw,
+						 unsigned long parent_rate)
+{
+	struct clk_imx_divider *divider = to_clk_imx_divider(hw);
+	unsigned int val;
+	int ret;
+
+	ret = imx_clk_divider_read(&divider->reg, &val);
+	if (ret)
+		return 0;
+
+	val >>= divider->shift;
+	val &= clk_div_mask(divider->width);
+
+	return divider_recalc_rate(hw, parent_rate, val, NULL, 0,
+				   divider->width);
+}
+
+static long imx_clk_divider_round_rate(struct clk_hw *hw, unsigned long rate,
+				       unsigned long *prate)
+{
+	struct clk_imx_divider *divider = to_clk_imx_divider(hw);
+
+	return divider_round_rate(hw, rate, prate, NULL, divider->width, 0);
+}
+
+static int imx_clk_divider_determine_rate(struct clk_hw *hw,
+					  struct clk_rate_request *req)
+{
+	struct clk_imx_divider *divider = to_clk_imx_divider(hw);
+
+	return divider_determine_rate(hw, req, NULL, divider->width, 0);
+}
+
+static int imx_clk_divider_set_rate(struct clk_hw *hw, unsigned long rate,
+				    unsigned long parent_rate)
+{
+	struct clk_imx_divider *divider = to_clk_imx_divider(hw);
+	unsigned int val;
+	int div, ret;
+
+	div = divider_get_val(rate, parent_rate, NULL, divider->width, 0);
+	if (div < 0)
+		return div;
+
+	ret = imx_clk_divider_read(&divider->reg, &val);
+	if (ret)
+		return ret;
+
+	val &= ~(clk_div_mask(divider->width) << divider->shift);
+	val |= div << divider->shift;
+	return imx_clk_divider_write(&divider->reg, val);
+}
+
+const struct clk_ops imx_clk_divider_ops = {
+	.recalc_rate = imx_clk_divider_recalc_rate,
+	.round_rate = imx_clk_divider_round_rate,
+	.determine_rate = imx_clk_divider_determine_rate,
+	.set_rate = imx_clk_divider_set_rate,
+};
+
+static void imx_clk_hw_unregister_divider(struct clk_hw *hw)
+{
+	struct clk_imx_divider *divider = to_clk_imx_divider(hw);
+
+	clk_hw_unregister(hw);
+	kfree(divider);
+}
+
+static struct clk_hw *imx_clk_hw_register_divider(struct device_node *node,
+						  const char *name,
+						  unsigned long flags,
+						  struct imx_clk_reg *reg,
+						  u8 shift, u8 width)
+{
+	struct clk_parent_data pdata = { .index = 0 };
+	struct clk_init_data init = { NULL };
+	struct clk_imx_divider *divider;
+	struct clk_hw *hw;
+	int ret;
+
+	divider = kzalloc(sizeof(*divider), GFP_KERNEL);
+	if (!divider)
+		return ERR_PTR(-ENOMEM);
+
+	init.name = name;
+	init.flags = flags;
+	init.ops = &imx_clk_divider_ops;
+	init.parent_data = &pdata;
+	init.num_parents = 1;
+
+	memcpy(&divider->reg, reg, sizeof(*reg));
+	divider->shift = shift;
+	divider->width = width;
+	divider->hw.init = &init;
+
+	hw = &divider->hw;
+	ret = of_clk_hw_register(node, hw);
+	if (ret) {
+		kfree(divider);
+		return ERR_PTR(ret);
+	}
+
+	return hw;
+}
+
+/**
+ * of_imx_divider_clk_setup() - Setup function for imx gate clock
+ * @node:	device node for the clock
+ */
+static void __init of_imx_divider_clk_setup(struct device_node *node)
+{
+	struct clk_hw *hw;
+	struct imx_clk_reg reg = {};
+	const char *name = node->name;
+	u8 shift = 0;
+	u8 width;
+	u32 flags = 0;
+	u32 val;
+
+	reg.regmap = syscon_regmap_lookup_by_phandle(node, "fsl,anatop");
+	if (!IS_ERR(reg.regmap)) {
+		if (of_property_read_u32_index(node, "fsl,anatop", 1, &val)) {
+			pr_err("missing register offset for %pOFn\n", node);
+			return;
+		}
+
+		reg.offset = val;
+	} else {
+		reg.base = of_iomap(node, 0);
+		if (IS_ERR(reg.base)) {
+			pr_err("failed to get register address for %pOFn\n",
+			       node);
+			return;
+		}
+	}
+
+	if (!of_property_read_u32(node, "fsl,bit-shift", &val))
+		shift = val;
+
+	if (of_property_read_u32(node, "fsl,width", &val)) {
+		pr_err("missing width for %pOFn\n", node);
+		return;
+
+	}
+
+	width = val;
+
+	if (of_property_read_bool(node, "fsl,ops-parent-enable"))
+		flags |= CLK_OPS_PARENT_ENABLE;
+
+	if (of_property_read_bool(node, "fsl,set-rate-parent"))
+		flags |= CLK_SET_RATE_PARENT;
+
+	if (of_clk_get_parent_count(node) != 1) {
+		pr_err("%pOFn must have 1 parent clock\n", node);
+		return;
+	}
+
+	of_property_read_string(node, "clock-output-names", &name);
+
+	hw = imx_clk_hw_register_divider(node, name, flags, &reg, shift, width);
+	if (IS_ERR(hw))
+		return;
+
+	if (of_clk_add_hw_provider(node, of_clk_hw_simple_get, hw)) {
+		imx_clk_hw_unregister_divider(hw);
+		return;
+	}
+
+	pr_debug("name: %s, offset: 0x%x, shift: %d, width: %d\n", name,
+		 reg.offset, shift, width);
+}
+CLK_OF_DECLARE(fsl_imx8mn_divider_clk, "fsl,imx8mn-divider-clock",
+	       of_imx_divider_clk_setup);
-- 
2.32.0