clk: sunxi: Add sun9i A80 cpus (cpu special) clock support

The "cpus" clock is the clock for the embedded processor in the A80.
It is also part of the PRCM clock tree. This clock includes a pre-
divider on one of its inputs. For now we are using a custom clock
driver for it. In the future we may want to develop a generalized
driver for these types of clocks, which also includes the AHB clock
driver on sun[5678]i.
Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

Documentation/devicetree/bindings/clock/sunxi.txt

@@ -27,6 +27,7 @@ Required properties:
 	"allwinner,sun5i-a10s-ahb-gates-clk" - for the AHB gates on A10s
 	"allwinner,sun7i-a20-ahb-gates-clk" - for the AHB gates on A20
 	"allwinner,sun6i-a31-ar100-clk" - for the AR100 on A31
+	"allwinner,sun9i-a80-cpus-clk" - for the CPUS on A80
 	"allwinner,sun6i-a31-ahb1-clk" - for the AHB1 clock on A31
 	"allwinner,sun6i-a31-ahb1-gates-clk" - for the AHB1 gates on A31
 	"allwinner,sun8i-a23-ahb1-gates-clk" - for the AHB1 gates on A23

drivers/clk/sunxi/Makefile

@@ -15,6 +15,8 @@ obj-y += clk-sun9i-core.o
 obj-y += clk-sun9i-mmc.o
 obj-y += clk-usb.o
 
+obj-$(CONFIG_MACH_SUN9I) += clk-sun9i-cpus.o
+
 obj-$(CONFIG_MFD_SUN6I_PRCM) += \
 	clk-sun6i-ar100.o clk-sun6i-apb0.o clk-sun6i-apb0-gates.o \
 	clk-sun8i-apb0.o

drivers/clk/sunxi/clk-sun9i-cpus.c

+/*
+ * Copyright (C) 2015 Chen-Yu Tsai
+ *
+ * Chen-Yu Tsai <wens@csie.org>
+ *
+ * Allwinner A80 CPUS clock driver
+ *
+ */
+
+#include <linux/clk.h>
+#include <linux/clk-provider.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+
+static DEFINE_SPINLOCK(sun9i_a80_cpus_lock);
+
+/**
+ * sun9i_a80_cpus_clk_setup() - Setup function for a80 cpus composite clk
+ */
+
+#define SUN9I_CPUS_MAX_PARENTS		4
+#define SUN9I_CPUS_MUX_PARENT_PLL4	3
+#define SUN9I_CPUS_MUX_SHIFT		16
+#define SUN9I_CPUS_MUX_MASK		GENMASK(17, 16)
+#define SUN9I_CPUS_MUX_GET_PARENT(reg)	((reg & SUN9I_CPUS_MUX_MASK) >> \
+						SUN9I_CPUS_MUX_SHIFT)
+
+#define SUN9I_CPUS_DIV_SHIFT		4
+#define SUN9I_CPUS_DIV_MASK		GENMASK(5, 4)
+#define SUN9I_CPUS_DIV_GET(reg)		((reg & SUN9I_CPUS_DIV_MASK) >> \
+						SUN9I_CPUS_DIV_SHIFT)
+#define SUN9I_CPUS_DIV_SET(reg, div)	((reg & ~SUN9I_CPUS_DIV_MASK) | \
+						(div << SUN9I_CPUS_DIV_SHIFT))
+#define SUN9I_CPUS_PLL4_DIV_SHIFT	8
+#define SUN9I_CPUS_PLL4_DIV_MASK	GENMASK(12, 8)
+#define SUN9I_CPUS_PLL4_DIV_GET(reg)	((reg & SUN9I_CPUS_PLL4_DIV_MASK) >> \
+						SUN9I_CPUS_PLL4_DIV_SHIFT)
+#define SUN9I_CPUS_PLL4_DIV_SET(reg, div) ((reg & ~SUN9I_CPUS_PLL4_DIV_MASK) | \
+						(div << SUN9I_CPUS_PLL4_DIV_SHIFT))
+
+struct sun9i_a80_cpus_clk {
+	struct clk_hw hw;
+	void __iomem *reg;
+};
+
+#define to_sun9i_a80_cpus_clk(_hw) container_of(_hw, struct sun9i_a80_cpus_clk, hw)
+
+static unsigned long sun9i_a80_cpus_clk_recalc_rate(struct clk_hw *hw,
+						    unsigned long parent_rate)
+{
+	struct sun9i_a80_cpus_clk *cpus = to_sun9i_a80_cpus_clk(hw);
+	unsigned long rate;
+	u32 reg;
+
+	/* Fetch the register value */
+	reg = readl(cpus->reg);
+
+	/* apply pre-divider first if parent is pll4 */
+	if (SUN9I_CPUS_MUX_GET_PARENT(reg) == SUN9I_CPUS_MUX_PARENT_PLL4)
+		parent_rate /= SUN9I_CPUS_PLL4_DIV_GET(reg) + 1;
+
+	/* clk divider */
+	rate = parent_rate / (SUN9I_CPUS_DIV_GET(reg) + 1);
+
+	return rate;
+}
+
+static long sun9i_a80_cpus_clk_round(unsigned long rate, u8 *divp, u8 *pre_divp,
+				     u8 parent, unsigned long parent_rate)
+{
+	u8 div, pre_div = 1;
+
+	/*
+	 * clock can only divide, so we will never be able to achieve
+	 * frequencies higher than the parent frequency
+	 */
+	if (parent_rate && rate > parent_rate)
+		rate = parent_rate;
+
+	div = DIV_ROUND_UP(parent_rate, rate);
+
+	/* calculate pre-divider if parent is pll4 */
+	if (parent == SUN9I_CPUS_MUX_PARENT_PLL4 && div > 4) {
+		/* pre-divider is 1 ~ 32 */
+		if (div < 32) {
+			pre_div = div;
+			div = 1;
+		} else if (div < 64) {
+			pre_div = DIV_ROUND_UP(div, 2);
+			div = 2;
+		} else if (div < 96) {
+			pre_div = DIV_ROUND_UP(div, 3);
+			div = 3;
+		} else {
+			pre_div = DIV_ROUND_UP(div, 4);
+			div = 4;
+		}
+	}
+
+	/* we were asked to pass back divider values */
+	if (divp) {
+		*divp = div - 1;
+		*pre_divp = pre_div - 1;
+	}
+
+	return parent_rate / pre_div / div;
+}
+
+static int sun9i_a80_cpus_clk_determine_rate(struct clk_hw *clk,
+					     struct clk_rate_request *req)
+{
+	struct clk_hw *parent, *best_parent = NULL;
+	int i, num_parents;
+	unsigned long parent_rate, best = 0, child_rate, best_child_rate = 0;
+	unsigned long rate = req->rate;
+
+	/* find the parent that can help provide the fastest rate <= rate */
+	num_parents = clk_hw_get_num_parents(clk);
+	for (i = 0; i < num_parents; i++) {
+		parent = clk_hw_get_parent_by_index(clk, i);
+		if (!parent)
+			continue;
+		if (clk_hw_get_flags(clk) & CLK_SET_RATE_PARENT)
+			parent_rate = clk_hw_round_rate(parent, rate);
+		else
+			parent_rate = clk_hw_get_rate(parent);
+
+		child_rate = sun9i_a80_cpus_clk_round(rate, NULL, NULL, i,
+						      parent_rate);
+
+		if (child_rate <= rate && child_rate > best_child_rate) {
+			best_parent = parent;
+			best = parent_rate;
+			best_child_rate = child_rate;
+		}
+	}
+
+	if (!best_parent)
+		return -EINVAL;
+
+	req->best_parent_hw = best_parent;
+	req->best_parent_rate = best;
+	req->rate = best_child_rate;
+
+	return 0;
+}
+
+static int sun9i_a80_cpus_clk_set_rate(struct clk_hw *hw, unsigned long rate,
+				       unsigned long parent_rate)
+{
+	struct sun9i_a80_cpus_clk *cpus = to_sun9i_a80_cpus_clk(hw);
+	unsigned long flags;
+	u8 div, pre_div, parent;
+	u32 reg;
+
+	spin_lock_irqsave(&sun9i_a80_cpus_lock, flags);
+
+	reg = readl(cpus->reg);
+
+	/* need to know which parent is used to apply pre-divider */
+	parent = SUN9I_CPUS_MUX_GET_PARENT(reg);
+	sun9i_a80_cpus_clk_round(rate, &div, &pre_div, parent, parent_rate);
+
+	reg = SUN9I_CPUS_DIV_SET(reg, div);
+	reg = SUN9I_CPUS_PLL4_DIV_SET(reg, pre_div);
+	writel(reg, cpus->reg);
+
+	spin_unlock_irqrestore(&sun9i_a80_cpus_lock, flags);
+
+	return 0;
+}
+
+static const struct clk_ops sun9i_a80_cpus_clk_ops = {
+	.determine_rate	= sun9i_a80_cpus_clk_determine_rate,
+	.recalc_rate	= sun9i_a80_cpus_clk_recalc_rate,
+	.set_rate	= sun9i_a80_cpus_clk_set_rate,
+};
+
+static void sun9i_a80_cpus_setup(struct device_node *node)
+{
+	const char *clk_name = node->name;
+	const char *parents[SUN9I_CPUS_MAX_PARENTS];
+	struct resource res;
+	struct sun9i_a80_cpus_clk *cpus;
+	struct clk_mux *mux;
+	struct clk *clk;
+	int ret;
+
+	cpus = kzalloc(sizeof(*cpus), GFP_KERNEL);
+	if (!cpus)
+		return;
+
+	cpus->reg = of_io_request_and_map(node, 0, of_node_full_name(node));
+	if (IS_ERR(cpus->reg))
+		goto err_free_cpus;
+
+	of_property_read_string(node, "clock-output-names", &clk_name);
+
+	/* we have a mux, we will have >1 parents */
+	ret = of_clk_parent_fill(node, parents, SUN9I_CPUS_MAX_PARENTS);
+
+	mux = kzalloc(sizeof(*mux), GFP_KERNEL);
+	if (!mux)
+		goto err_unmap;
+
+	/* set up clock properties */
+	mux->reg = cpus->reg;
+	mux->shift = SUN9I_CPUS_MUX_SHIFT;
+	/* un-shifted mask is what mux_clk expects */
+	mux->mask = SUN9I_CPUS_MUX_MASK >> SUN9I_CPUS_MUX_SHIFT;
+	mux->lock = &sun9i_a80_cpus_lock;
+
+	clk = clk_register_composite(NULL, clk_name, parents, ret,
+				     &mux->hw, &clk_mux_ops,
+				     &cpus->hw, &sun9i_a80_cpus_clk_ops,
+				     NULL, NULL, 0);
+	if (IS_ERR(clk))
+		goto err_free_mux;
+
+	ret = of_clk_add_provider(node, of_clk_src_simple_get, clk);
+	if (ret)
+		goto err_unregister;
+
+	return;
+
+err_unregister:
+	clk_unregister(clk);
+err_free_mux:
+	kfree(mux);
+err_unmap:
+	iounmap(cpus->reg);
+	of_address_to_resource(node, 0, &res);
+	release_mem_region(res.start, resource_size(&res));
+err_free_cpus:
+	kfree(cpus);
+}
+CLK_OF_DECLARE(sun9i_a80_cpus, "allwinner,sun9i-a80-cpus-clk",
+	       sun9i_a80_cpus_setup);