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Subject[PATCH 2/2] clk: Add fractional scale clock support
Date
This patch adds fractional scale clock support.
Fractional scale clock is implemented for a single register field.
Output rate = parent_rate * scale / denominator
For example, for 1 / 8 fractional scale, denominator will be 8 and scale
will be computed and programmed accordingly.

Signed-off-by: Hoan Tran <hotran@apm.com>
Signed-off-by: Loc Ho <lho@apm.com>
---
drivers/clk/Makefile | 1 +
drivers/clk/clk-fractional-scale.c | 253 +++++++++++++++++++++++++++++++++++++
include/linux/clk-provider.h | 41 ++++++
3 files changed, 295 insertions(+)
create mode 100644 drivers/clk/clk-fractional-scale.c

diff --git a/drivers/clk/Makefile b/drivers/clk/Makefile
index dcc5e69..d7deddf 100644
--- a/drivers/clk/Makefile
+++ b/drivers/clk/Makefile
@@ -10,6 +10,7 @@ obj-$(CONFIG_COMMON_CLK) += clk-multiplier.o
obj-$(CONFIG_COMMON_CLK) += clk-mux.o
obj-$(CONFIG_COMMON_CLK) += clk-composite.o
obj-$(CONFIG_COMMON_CLK) += clk-fractional-divider.o
+obj-$(CONFIG_COMMON_CLK) += clk-fractional-scale.o
obj-$(CONFIG_COMMON_CLK) += clk-gpio.o
ifeq ($(CONFIG_OF), y)
obj-$(CONFIG_COMMON_CLK) += clk-conf.o
diff --git a/drivers/clk/clk-fractional-scale.c b/drivers/clk/clk-fractional-scale.c
new file mode 100644
index 0000000..1cf6f57
--- /dev/null
+++ b/drivers/clk/clk-fractional-scale.c
@@ -0,0 +1,253 @@
+/*
+ * Copyright (C) 2016 Applied Micro Circuits Corporation
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * Fractional scale clock is implemented for a single register field.
+ *
+ * Output rate = parent_rate * scale / denominator
+ *
+ * For example, for 1/8 fractional scale, denominator will be 8 and scale
+ * will be computed and programmed accordingly.
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/clkdev.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/of_address.h>
+#include <linux/slab.h>
+
+#define to_clk_sf(_hw) container_of(_hw, struct clk_fractional_scale, hw)
+
+static DEFINE_SPINLOCK(clk_lock);
+
+static unsigned long clk_fs_recalc_rate(struct clk_hw *hw,
+ unsigned long parent_rate)
+{
+ struct clk_fractional_scale *fd = to_clk_sf(hw);
+ unsigned long flags = 0;
+ u64 ret, scale;
+ u32 val;
+
+ if (fd->lock)
+ spin_lock_irqsave(fd->lock, flags);
+ else
+ __acquire(fd->lock);
+
+ val = clk_readl(fd->reg);
+
+ if (fd->lock)
+ spin_unlock_irqrestore(fd->lock, flags);
+ else
+ __release(fd->lock);
+
+ ret = (u64) parent_rate;
+
+ scale = (val & fd->mask) >> fd->shift;
+ if (fd->flags & CLK_FRACTIONAL_SCALE_INVERTED)
+ scale = fd->denom - scale;
+ else
+ scale++;
+
+ /* freq = parent_rate * scaler / denom */
+ do_div(ret, fd->denom);
+ ret *= scale;
+ if (ret == 0)
+ ret = (u64) parent_rate;
+
+ return ret;
+}
+
+static long clk_fs_round_rate(struct clk_hw *hw, unsigned long rate,
+ unsigned long *parent_rate)
+{
+ struct clk_fractional_scale *fd = to_clk_sf(hw);
+ u64 ret, scale;
+
+ if (!rate || rate >= *parent_rate)
+ return *parent_rate;
+
+ /* freq = parent_rate * scaler / denom */
+ ret = rate * fd->denom;
+ scale = ret / *parent_rate;
+
+ ret = (u64) *parent_rate * scale;
+ do_div(ret, fd->denom);
+
+ return ret;
+}
+
+static int clk_fs_set_rate(struct clk_hw *hw, unsigned long rate,
+ unsigned long parent_rate)
+{
+ struct clk_fractional_scale *fd = to_clk_sf(hw);
+ unsigned long flags = 0;
+ u64 scale, ret;
+ u32 val;
+
+ /*
+ * Compute the scaler:
+ *
+ * freq = parent_rate * scaler / denom, or
+ * scaler = freq * denom / parent_rate
+ */
+ ret = rate * fd->denom;
+ scale = ret / (u64)parent_rate;
+
+ /* Check if inverted */
+ if (fd->flags & CLK_FRACTIONAL_SCALE_INVERTED)
+ scale = fd->denom - scale;
+ else
+ scale--;
+
+ if (fd->lock)
+ spin_lock_irqsave(fd->lock, flags);
+ else
+ __acquire(fd->lock);
+
+ val = clk_readl(fd->reg);
+ val &= ~fd->mask;
+ val |= (scale << fd->shift);
+ clk_writel(val, fd->reg);
+
+ if (fd->lock)
+ spin_unlock_irqrestore(fd->lock, flags);
+ else
+ __release(fd->lock);
+
+ return 0;
+}
+
+const struct clk_ops clk_fractional_scale_ops = {
+ .recalc_rate = clk_fs_recalc_rate,
+ .round_rate = clk_fs_round_rate,
+ .set_rate = clk_fs_set_rate,
+};
+EXPORT_SYMBOL_GPL(clk_fractional_scale_ops);
+
+struct clk_hw *clk_hw_register_fractional_scale(struct device *dev,
+ const char *name, const char *parent_name, unsigned long flags,
+ void __iomem *reg, u8 shift, u8 width, u64 denom,
+ u32 clk_flags, spinlock_t *lock)
+{
+ struct clk_fractional_scale *fd;
+ struct clk_init_data init;
+ struct clk_hw *hw;
+ int ret;
+
+ fd = kzalloc(sizeof(*fd), GFP_KERNEL);
+ if (!fd)
+ return ERR_PTR(-ENOMEM);
+
+ init.name = name;
+ init.ops = &clk_fractional_scale_ops;
+ init.flags = flags | CLK_IS_BASIC;
+ init.parent_names = parent_name ? &parent_name : NULL;
+ init.num_parents = parent_name ? 1 : 0;
+
+ fd->reg = reg;
+ fd->shift = shift;
+ fd->mask = (BIT(width) - 1) << shift;
+ fd->denom = denom;
+ fd->flags = clk_flags;
+ fd->lock = lock;
+ fd->hw.init = &init;
+
+ hw = &fd->hw;
+ ret = clk_hw_register(dev, hw);
+ if (ret) {
+ kfree(fd);
+ hw = ERR_PTR(ret);
+ }
+
+ return hw;
+}
+EXPORT_SYMBOL_GPL(clk_hw_register_fractional_scale);
+
+struct clk *clk_register_fractional_scale(struct device *dev,
+ const char *name, const char *parent_name, unsigned long flags,
+ void __iomem *reg, u8 shift, u8 width, u64 denom,
+ u32 clk_flags, spinlock_t *lock)
+{
+ struct clk_hw *hw;
+
+ hw = clk_hw_register_fractional_scale(dev, name, parent_name, flags,
+ reg, shift, width, denom,
+ clk_flags, lock);
+ if (IS_ERR(hw))
+ return ERR_CAST(hw);
+
+ return hw->clk;
+}
+EXPORT_SYMBOL_GPL(clk_register_fractional_scale);
+
+void clk_hw_unregister_fractional_scale(struct clk_hw *hw)
+{
+ struct clk_fractional_scale *fd;
+
+ fd = to_clk_sf(hw);
+
+ clk_hw_unregister(hw);
+ kfree(fd);
+}
+EXPORT_SYMBOL_GPL(clk_hw_unregister_fractional_scale);
+
+static void __init clk_fractional_scale_init(struct device_node *np)
+{
+ const char *clk_name = np->full_name;
+ u32 shift, width, inverted;
+ void __iomem *csr_reg;
+ struct resource res;
+ struct clk *clk;
+ u32 flags = 0;
+ u64 denom;
+ int rc;
+
+ /* Check if the entry is disabled */
+ if (!of_device_is_available(np))
+ return;
+
+ /* Parse the DTS register for resource */
+ rc = of_address_to_resource(np, 0, &res);
+ if (rc != 0) {
+ pr_err("No DTS register for %s\n", np->full_name);
+ return;
+ }
+ csr_reg = of_iomap(np, 0);
+ if (csr_reg == NULL) {
+ pr_err("Unable to map resource for %s\n", np->full_name);
+ return;
+ }
+ if (of_property_read_u32(np, "clock-shift", &shift))
+ shift = 0;
+ if (of_property_read_u32(np, "clock-width", &width))
+ width = 32;
+ if (of_property_read_u64(np, "clock-denom", &denom))
+ denom = BIT(width);
+ if (of_property_read_u32(np, "clock-inverted", &inverted))
+ inverted = 0;
+ of_property_read_string(np, "clock-output-names", &clk_name);
+
+ if (inverted)
+ flags |= CLK_FRACTIONAL_SCALE_INVERTED;
+
+ clk = clk_register_fractional_scale(NULL, clk_name,
+ of_clk_get_parent_name(np, 0), 0,
+ csr_reg, shift, width, denom,
+ flags, &clk_lock);
+ if (!IS_ERR(clk)) {
+ of_clk_add_provider(np, of_clk_src_simple_get, clk);
+ clk_register_clkdev(clk, clk_name, NULL);
+ pr_debug("Add %s clock\n", clk_name);
+ } else {
+ if (csr_reg)
+ iounmap(csr_reg);
+ }
+}
+
+CLK_OF_DECLARE(fractional_scale_clock, "fractional-scale-clock",
+ clk_fractional_scale_init);
diff --git a/include/linux/clk-provider.h b/include/linux/clk-provider.h
index 0c72204..7d33bc0 100644
--- a/include/linux/clk-provider.h
+++ b/include/linux/clk-provider.h
@@ -578,6 +578,47 @@ struct clk_hw *clk_hw_register_fractional_divider(struct device *dev,
void clk_hw_unregister_fractional_divider(struct clk_hw *hw);

/**
+ * struct clk_fractional_scale - Fractional scale clock
+ *
+ * @hw: handle between common and hardware-specific interfaces
+ * @reg: register containing the fractional scale multiplier (scaler)
+ * @shift: shift to the unit bit field
+ * @width: width of the unit bit field
+ * @denom: 1/denominator unit
+ * @lock: register lock
+ *
+ * Clock with fractional scale affecting its output frequency.
+ *
+ * Flags:
+ * CLK_FRACTIONAL_SCALE_INVERTED - by default the scaler is the value read
+ * from the register plus one. For example,
+ * 0 for (0 + 1) / denom,
+ * 1 for (1 + 1) / denom and etc.
+ * If this flag is set, it is
+ * 0 for (denom - 0) / denom,
+ * 1 for (denom - 1) / denom and etc.
+ */
+
+struct clk_fractional_scale {
+ struct clk_hw hw;
+ void __iomem *reg;
+ u8 shift;
+ u32 mask;
+ u64 denom;
+ u32 flags;
+ spinlock_t *lock;
+};
+
+#define CLK_FRACTIONAL_SCALE_INVERTED BIT(0)
+
+extern const struct clk_ops clk_fractional_scale_ops;
+struct clk *clk_register_fractional_scale(struct device *dev,
+ const char *name, const char *parent_name, unsigned long flags,
+ void __iomem *reg, u8 shift, u8 width, u64 denom,
+ u32 clk_flags, spinlock_t *lock);
+
+
+/**
* struct clk_multiplier - adjustable multiplier clock
*
* @hw: handle between common and hardware-specific interfaces
--
1.9.1
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