[PATCH v5 09/27] clk: ti: add divider clock driver

25 Oct 2020

The patch adds support for TI divider clock binding. The driver uses
routines provided by the common clock framework (ccf).
The code is based on the drivers/clk/ti/divider.c driver of the Linux
kernel version 5.9-rc7.
For DT binding details see:
- Documentation/devicetree/bindings/clock/ti/divider.txt
Signed-off-by: Dario Binacchi dariobin@libero.it
---
Changes in v5:
- Move the clk-ti.c file to drivers/clk/ti with the name clk.c.
- Move the clk-ti.h file to drivers/clk/ti with the name clk.h.
- Move the clk-ti-divider.c file to drivers/clk/ti with the name
  clk-divider.c.
Changes in v4:
- Include device_compat.h header for dev_xxx macros.
- Fix compilation errors on the dev parameter of the dev_xx macros.
Changes in v3:
- Remove doc/device-tree-bindings/clock/ti,autoidle.txt.
- Remove doc/device-tree-bindings/clock/ti,divider.txt.
- Add to commit message the references to linux kernel dt binding
  documentation.
Changes in v2:
- Merged to patch [09/31] clk: ti: refactor mux and divider clock
  drivers.
drivers/clk/ti/Kconfig       |   6 +
 drivers/clk/ti/Makefile      |   3 +
 drivers/clk/ti/clk-divider.c | 381 +++++++++++++++++++++++++++++++++++
 drivers/clk/ti/clk-mux.c     |  27 +--
 drivers/clk/ti/clk.c         |  34 ++++
 drivers/clk/ti/clk.h         |  13 ++
 6 files changed, 439 insertions(+), 25 deletions(-)
 create mode 100644 drivers/clk/ti/clk-divider.c
 create mode 100644 drivers/clk/ti/clk.c
 create mode 100644 drivers/clk/ti/clk.h

diff --git a/drivers/clk/ti/Kconfig b/drivers/clk/ti/Kconfig
index c430dd9b8a..87eea86c6f 100644
--- a/drivers/clk/ti/Kconfig
+++ b/drivers/clk/ti/Kconfig
@@ -10,6 +10,12 @@ config CLK_TI_AM3_DPLL
      This enables the DPLL clock drivers support on AM33XX SoCs. The DPLL
      provides all interface clocks and functional clocks to the processor.
+config CLK_TI_DIVIDER
+	bool "TI divider clock driver"
+	depends on CLK && OF_CONTROL && CLK_CCF
+	help
+	  This enables the divider clock driver support on TI's SoCs.
+
 config CLK_TI_MUX
    bool "TI mux clock driver"
    depends on CLK && OF_CONTROL && CLK_CCF
diff --git a/drivers/clk/ti/Makefile b/drivers/clk/ti/Makefile
index 9e14b83cfe..fd7094cff0 100644
--- a/drivers/clk/ti/Makefile
+++ b/drivers/clk/ti/Makefile
@@ -3,5 +3,8 @@
 # Copyright (C) 2020 Dario Binacchi dariobin@libero.it
 #
+obj-$(CONFIG_ARCH_OMAP2PLUS) += clk.o
+
 obj-$(CONFIG_CLK_TI_AM3_DPLL) += clk-am3-dpll.o clk-am3-dpll-x2.o
+obj-$(CONFIG_CLK_TI_DIVIDER) += clk-divider.o
 obj-$(CONFIG_CLK_TI_MUX) += clk-mux.o
diff --git a/drivers/clk/ti/clk-divider.c b/drivers/clk/ti/clk-divider.c
new file mode 100644
index 0000000000..d448197b1f
--- /dev/null
+++ b/drivers/clk/ti/clk-divider.c
@@ -0,0 +1,381 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * TI divider clock support
+ *
+ * Copyright (C) 2020 Dario Binacchi dariobin@libero.it
+ *
+ * Loosely based on Linux kernel drivers/clk/ti/divider.c
+ */
+
+#include <common.h>
+#include <clk.h>
+#include <clk-uclass.h>
+#include <div64.h>
+#include <dm.h>
+#include <dm/device_compat.h>
+#include <asm/io.h>
+#include <linux/clk-provider.h>
+#include <linux/kernel.h>
+#include <linux/log2.h>
+#include "clk.h"
+
+/*
+ * The reverse of DIV_ROUND_UP: The maximum number which
+ * divided by m is r
+ */
+#define MULT_ROUND_UP(r, m) ((r) * (m) + (m) - 1)
+
+struct clk_ti_divider_priv {
+	struct clk parent;
+	fdt_addr_t reg;
+	const struct clk_div_table *table;
+	u8 shift;
+	u8 flags;
+	u8 div_flags;
+	s8 latch;
+	u16 min;
+	u16 max;
+	u16 mask;
+};
+
+static unsigned int _get_div(const struct clk_div_table *table, ulong flags,
+			     unsigned int val)
+{
+	if (flags & CLK_DIVIDER_ONE_BASED)
+		return val;
+
+	if (flags & CLK_DIVIDER_POWER_OF_TWO)
+		return 1 << val;
+
+	if (table)
+		return clk_divider_get_table_div(table, val);
+
+	return val + 1;
+}
+
+static unsigned int _get_val(const struct clk_div_table *table, ulong flags,
+			     unsigned int div)
+{
+	if (flags & CLK_DIVIDER_ONE_BASED)
+		return div;
+
+	if (flags & CLK_DIVIDER_POWER_OF_TWO)
+		return __ffs(div);
+
+	if (table)
+		return clk_divider_get_table_val(table, div);
+
+	return div - 1;
+}
+
+static int _div_round_up(const struct clk_div_table *table, ulong parent_rate,
+			 ulong rate)
+{
+	const struct clk_div_table *clkt;
+	int up = INT_MAX;
+	int div = DIV_ROUND_UP_ULL((u64)parent_rate, rate);
+
+	for (clkt = table; clkt->div; clkt++) {
+		if (clkt->div == div)
+			return clkt->div;
+		else if (clkt->div < div)
+			continue;
+
+		if ((clkt->div - div) < (up - div))
+			up = clkt->div;
+	}
+
+	return up;
+}
+
+static int _div_round(const struct clk_div_table *table, ulong parent_rate,
+		      ulong rate)
+{
+	if (table)
+		return _div_round_up(table, parent_rate, rate);
+
+	return DIV_ROUND_UP(parent_rate, rate);
+}
+
+static int clk_ti_divider_best_div(struct clk *clk, ulong rate,
+				   ulong *best_parent_rate)
+{
+	struct clk_ti_divider_priv *priv = dev_get_priv(clk->dev);
+	ulong parent_rate, parent_round_rate, max_div;
+	ulong best_rate, r;
+	int i, best_div = 0;
+
+	parent_rate = clk_get_rate(&priv->parent);
+	if (IS_ERR_VALUE(parent_rate))
+		return parent_rate;
+
+	if (!rate)
+		rate = 1;
+
+	if (!(clk->flags & CLK_SET_RATE_PARENT)) {
+		best_div = _div_round(priv->table, parent_rate, rate);
+		if (best_div == 0)
+			best_div = 1;
+
+		if (best_div > priv->max)
+			best_div = priv->max;
+
+		*best_parent_rate = parent_rate;
+		return best_div;
+	}
+
+	max_div = min(ULONG_MAX / rate, (ulong)priv->max);
+	for (best_rate = 0, i = 1; i <= max_div; i++) {
+		if (!clk_divider_is_valid_div(priv->table, priv->div_flags, i))
+			continue;
+
+		/*
+		 * It's the most ideal case if the requested rate can be
+		 * divided from parent clock without needing to change
+		 * parent rate, so return the divider immediately.
+		 */
+		if ((rate * i) == parent_rate) {
+			*best_parent_rate = parent_rate;
+			dev_dbg(clk->dev, "rate=%ld, best_rate=%ld, div=%d\n",
+				rate, rate, i);
+			return i;
+		}
+
+		parent_round_rate = clk_round_rate(&priv->parent,
+						   MULT_ROUND_UP(rate, i));
+		if (IS_ERR_VALUE(parent_round_rate))
+			continue;
+
+		r = DIV_ROUND_UP(parent_round_rate, i);
+		if (r <= rate && r > best_rate) {
+			best_div = i;
+			best_rate = r;
+			*best_parent_rate = parent_round_rate;
+			if (best_rate == rate)
+				break;
+		}
+	}
+
+	if (best_div == 0) {
+		best_div = priv->max;
+		parent_round_rate = clk_round_rate(&priv->parent, 1);
+		if (IS_ERR_VALUE(parent_round_rate))
+			return parent_round_rate;
+	}
+
+	dev_dbg(clk->dev, "rate=%ld, best_rate=%ld, div=%d\n", rate, best_rate,
+		best_div);
+
+	return best_div;
+}
+
+static ulong clk_ti_divider_round_rate(struct clk *clk, ulong rate)
+{
+	ulong parent_rate;
+	int div;
+
+	div = clk_ti_divider_best_div(clk, rate, &parent_rate);
+	if (div < 0)
+		return div;
+
+	return DIV_ROUND_UP(parent_rate, div);
+}
+
+static ulong clk_ti_divider_set_rate(struct clk *clk, ulong rate)
+{
+	struct clk_ti_divider_priv *priv = dev_get_priv(clk->dev);
+	ulong parent_rate;
+	int div;
+	u32 val, v;
+
+	div = clk_ti_divider_best_div(clk, rate, &parent_rate);
+	if (div < 0)
+		return div;
+
+	if (clk->flags & CLK_SET_RATE_PARENT) {
+		parent_rate = clk_set_rate(&priv->parent, parent_rate);
+		if (IS_ERR_VALUE(parent_rate))
+			return parent_rate;
+	}
+
+	val = _get_val(priv->table, priv->div_flags, div);
+
+	v = readl(priv->reg);
+	v &= ~(priv->mask << priv->shift);
+	v |= val << priv->shift;
+	writel(v, priv->reg);
+	clk_ti_latch(priv->reg, priv->latch);
+
+	return clk_get_rate(clk);
+}
+
+static ulong clk_ti_divider_get_rate(struct clk *clk)
+{
+	struct clk_ti_divider_priv *priv = dev_get_priv(clk->dev);
+	ulong rate, parent_rate;
+	unsigned int div;
+	u32 v;
+
+	parent_rate = clk_get_rate(&priv->parent);
+	if (IS_ERR_VALUE(parent_rate))
+		return parent_rate;
+
+	v = readl(priv->reg) >> priv->shift;
+	v &= priv->mask;
+
+	div = _get_div(priv->table, priv->div_flags, v);
+	if (!div) {
+		if (!(priv->div_flags & CLK_DIVIDER_ALLOW_ZERO))
+			dev_warn(clk->dev,
+				 "zero divisor and CLK_DIVIDER_ALLOW_ZERO not set\n");
+		return parent_rate;
+	}
+
+	rate = DIV_ROUND_UP(parent_rate, div);
+	dev_dbg(clk->dev, "rate=%ld\n", rate);
+	return rate;
+}
+
+static int clk_ti_divider_request(struct clk *clk)
+{
+	struct clk_ti_divider_priv *priv = dev_get_priv(clk->dev);
+
+	clk->flags = priv->flags;
+	return 0;
+}
+
+const struct clk_ops clk_ti_divider_ops = {
+	.request = clk_ti_divider_request,
+	.round_rate = clk_ti_divider_round_rate,
+	.get_rate = clk_ti_divider_get_rate,
+	.set_rate = clk_ti_divider_set_rate
+};
+
+static int clk_ti_divider_remove(struct udevice *dev)
+{
+	struct clk_ti_divider_priv *priv = dev_get_priv(dev);
+	int err;
+
+	err = clk_release_all(&priv->parent, 1);
+	if (err) {
+		dev_err(dev, "failed to release parent clock\n");
+		return err;
+	}
+
+	return 0;
+}
+
+static int clk_ti_divider_probe(struct udevice *dev)
+{
+	struct clk_ti_divider_priv *priv = dev_get_priv(dev);
+	int err;
+
+	err = clk_get_by_index(dev, 0, &priv->parent);
+	if (err) {
+		dev_err(dev, "failed to get parent clock\n");
+		return err;
+	}
+
+	return 0;
+}
+
+static int clk_ti_divider_ofdata_to_platdata(struct udevice *dev)
+{
+	struct clk_ti_divider_priv *priv = dev_get_priv(dev);
+	struct clk_div_table *table = NULL;
+	u32 val, valid_div;
+	u32 min_div = 0;
+	u32 max_val, max_div = 0;
+	u16 mask;
+	int i, div_num;
+
+	priv->reg = dev_read_addr(dev);
+	dev_dbg(dev, "reg=0x%08lx\n", priv->reg);
+	priv->shift = dev_read_u32_default(dev, "ti,bit-shift", 0);
+	priv->latch = dev_read_s32_default(dev, "ti,latch-bit", -EINVAL);
+	if (dev_read_bool(dev, "ti,index-starts-at-one"))
+		priv->div_flags |= CLK_DIVIDER_ONE_BASED;
+
+	if (dev_read_bool(dev, "ti,index-power-of-two"))
+		priv->div_flags |= CLK_DIVIDER_POWER_OF_TWO;
+
+	if (dev_read_bool(dev, "ti,set-rate-parent"))
+		priv->flags |= CLK_SET_RATE_PARENT;
+
+	if (dev_read_prop(dev, "ti,dividers", &div_num)) {
+		div_num /= sizeof(u32);
+
+		/* Determine required size for divider table */
+		for (i = 0, valid_div = 0; i < div_num; i++) {
+			dev_read_u32_index(dev, "ti,dividers", i, &val);
+			if (val)
+				valid_div++;
+		}
+
+		if (!valid_div) {
+			dev_err(dev, "no valid dividers\n");
+			return -EINVAL;
+		}
+
+		table = calloc(valid_div + 1, sizeof(*table));
+		if (!table)
+			return -ENOMEM;
+
+		for (i = 0, valid_div = 0; i < div_num; i++) {
+			dev_read_u32_index(dev, "ti,dividers", i, &val);
+			if (!val)
+				continue;
+
+			table[valid_div].div = val;
+			table[valid_div].val = i;
+			valid_div++;
+			if (val > max_div)
+				max_div = val;
+
+			if (!min_div || val < min_div)
+				min_div = val;
+		}
+
+		max_val = max_div;
+	} else {
+		/* Divider table not provided, determine min/max divs */
+		min_div = dev_read_u32_default(dev, "ti,min-div", 1);
+		if (dev_read_u32(dev, "ti,max-div", &max_div)) {
+			dev_err(dev, "missing 'max-div' property\n");
+			return -EFAULT;
+		}
+
+		max_val = max_div;
+		if (!(priv->div_flags & CLK_DIVIDER_ONE_BASED) &&
+		    !(priv->div_flags & CLK_DIVIDER_POWER_OF_TWO))
+			max_val--;
+	}
+
+	priv->table = table;
+	priv->min = min_div;
+	priv->max = max_div;
+
+	if (priv->div_flags & CLK_DIVIDER_POWER_OF_TWO)
+		mask = fls(max_val) - 1;
+	else
+		mask = max_val;
+
+	priv->mask = (1 << fls(mask)) - 1;
+	return 0;
+}
+
+static const struct udevice_id clk_ti_divider_of_match[] = {
+	{.compatible = "ti,divider-clock"},
+	{}
+};
+
+U_BOOT_DRIVER(clk_ti_divider) = {
+	.name = "ti_divider_clock",
+	.id = UCLASS_CLK,
+	.of_match = clk_ti_divider_of_match,
+	.ofdata_to_platdata = clk_ti_divider_ofdata_to_platdata,
+	.probe = clk_ti_divider_probe,
+	.remove = clk_ti_divider_remove,
+	.priv_auto_alloc_size = sizeof(struct clk_ti_divider_priv),
+	.ops = &clk_ti_divider_ops,
+};
diff --git a/drivers/clk/ti/clk-mux.c b/drivers/clk/ti/clk-mux.c
index 9720c84513..35470255af 100644
--- a/drivers/clk/ti/clk-mux.c
+++ b/drivers/clk/ti/clk-mux.c
@@ -13,6 +13,7 @@
 #include <clk-uclass.h>
 #include <asm/io.h>
 #include <linux/clk-provider.h>
+#include "clk.h"
struct clk_ti_mux_priv {
    struct clk_bulk parents;
@@ -24,30 +25,6 @@ struct clk_ti_mux_priv {
    s32 latch;
 };
-static void clk_ti_mux_rmw(u32 val, u32 mask, fdt_addr_t reg)
-{
-	u32 v;
-
-	v = readl(reg);
-	v &= ~mask;
-	v |= val;
-	writel(v, reg);
-}
-
-static void clk_ti_mux_latch(fdt_addr_t reg, s8 shift)
-{
-	u32 latch;
-
-	if (shift < 0)
-		return;
-
-	latch = 1 << shift;
-
-	clk_ti_mux_rmw(latch, latch, reg);
-	clk_ti_mux_rmw(0, latch, reg);
-	readl(reg);		/* OCP barrier */
-}
-
 static struct clk *clk_ti_mux_get_parent_by_index(struct clk_bulk *parents,
    					  int index)
 {
@@ -120,7 +97,7 @@ static int clk_ti_mux_set_parent(struct clk *clk, struct clk *parent)
val |= index << priv->shift;
    writel(val, priv->reg);
-	clk_ti_mux_latch(priv->reg, priv->latch);
+	clk_ti_latch(priv->reg, priv->latch);
    return 0;
 }
diff --git a/drivers/clk/ti/clk.c b/drivers/clk/ti/clk.c
new file mode 100644
index 0000000000..e44b90ad6a
--- /dev/null
+++ b/drivers/clk/ti/clk.c
@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * TI clock utilities
+ *
+ * Copyright (C) 2020 Dario Binacchi dariobin@libero.it
+ */
+
+#include <common.h>
+#include <asm/io.h>
+#include "clk.h"
+
+static void clk_ti_rmw(u32 val, u32 mask, fdt_addr_t reg)
+{
+	u32 v;
+
+	v = readl(reg);
+	v &= ~mask;
+	v |= val;
+	writel(v, reg);
+}
+
+void clk_ti_latch(fdt_addr_t reg, s8 shift)
+{
+	u32 latch;
+
+	if (shift < 0)
+		return;
+
+	latch = 1 << shift;
+
+	clk_ti_rmw(latch, latch, reg);
+	clk_ti_rmw(0, latch, reg);
+	readl(reg);		/* OCP barrier */
+}
diff --git a/drivers/clk/ti/clk.h b/drivers/clk/ti/clk.h
new file mode 100644
index 0000000000..601c3823f7
--- /dev/null
+++ b/drivers/clk/ti/clk.h
@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ * TI clock utilities header
+ *
+ * Copyright (C) 2020 Dario Binacchi dariobin@libero.it
+ */
+
+#ifndef _CLK_TI_H
+#define _CLK_TI_H
+
+void clk_ti_latch(fdt_addr_t reg, s8 shift);
+
+#endif /* #ifndef _CLK_TI_H */
-- 
2.17.1


    