clk: sunxi: unify sun6i AHB1 clock with proper PLL6 pre-divider

This patch unifies the sun6i AHB1 clock, originally supported
with separate mux and divider clks. It also adds support for
the pre-divider on the PLL6 input, thus allowing the clock to
be muxed to PLL6 with proper clock rate calculation.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

Documentation/devicetree/bindings/clock/sunxi.txt

@@ -26,7 +26,7 @@ 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,sun6i-a31-ahb1-mux-clk" - for the AHB1 multiplexer on A31
+	"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
 	"allwinner,sun9i-a80-ahb0-gates-clk" - for the AHB0 gates on A80

drivers/clk/sunxi/clk-sunxi.c

@@ -20,11 +20,219 @@
 #include <linux/of_address.h>
 #include <linux/reset-controller.h>
 #include <linux/spinlock.h>
+#include <linux/log2.h>
 
 #include "clk-factors.h"
 
 static DEFINE_SPINLOCK(clk_lock);
 
+/**
+ * sun6i_a31_ahb1_clk_setup() - Setup function for a31 ahb1 composite clk
+ */
+
+#define SUN6I_AHB1_MAX_PARENTS		4
+#define SUN6I_AHB1_MUX_PARENT_PLL6	3
+#define SUN6I_AHB1_MUX_SHIFT		12
+/* un-shifted mask is what mux_clk expects */
+#define SUN6I_AHB1_MUX_MASK		0x3
+#define SUN6I_AHB1_MUX_GET_PARENT(reg)	((reg >> SUN6I_AHB1_MUX_SHIFT) & \
+					 SUN6I_AHB1_MUX_MASK)
+
+#define SUN6I_AHB1_DIV_SHIFT		4
+#define SUN6I_AHB1_DIV_MASK		(0x3 << SUN6I_AHB1_DIV_SHIFT)
+#define SUN6I_AHB1_DIV_GET(reg)		((reg & SUN6I_AHB1_DIV_MASK) >> \
+						SUN6I_AHB1_DIV_SHIFT)
+#define SUN6I_AHB1_DIV_SET(reg, div)	((reg & ~SUN6I_AHB1_DIV_MASK) | \
+						(div << SUN6I_AHB1_DIV_SHIFT))
+#define SUN6I_AHB1_PLL6_DIV_SHIFT	6
+#define SUN6I_AHB1_PLL6_DIV_MASK	(0x3 << SUN6I_AHB1_PLL6_DIV_SHIFT)
+#define SUN6I_AHB1_PLL6_DIV_GET(reg)	((reg & SUN6I_AHB1_PLL6_DIV_MASK) >> \
+						SUN6I_AHB1_PLL6_DIV_SHIFT)
+#define SUN6I_AHB1_PLL6_DIV_SET(reg, div) ((reg & ~SUN6I_AHB1_PLL6_DIV_MASK) | \
+						(div << SUN6I_AHB1_PLL6_DIV_SHIFT))
+
+struct sun6i_ahb1_clk {
+	struct clk_hw hw;
+	void __iomem *reg;
+};
+
+#define to_sun6i_ahb1_clk(_hw) container_of(_hw, struct sun6i_ahb1_clk, hw)
+
+static unsigned long sun6i_ahb1_clk_recalc_rate(struct clk_hw *hw,
+						unsigned long parent_rate)
+{
+	struct sun6i_ahb1_clk *ahb1 = to_sun6i_ahb1_clk(hw);
+	unsigned long rate;
+	u32 reg;
+
+	/* Fetch the register value */
+	reg = readl(ahb1->reg);
+
+	/* apply pre-divider first if parent is pll6 */
+	if (SUN6I_AHB1_MUX_GET_PARENT(reg) == SUN6I_AHB1_MUX_PARENT_PLL6)
+		parent_rate /= SUN6I_AHB1_PLL6_DIV_GET(reg) + 1;
+
+	/* clk divider */
+	rate = parent_rate >> SUN6I_AHB1_DIV_GET(reg);
+
+	return rate;
+}
+
+static long sun6i_ahb1_clk_round(unsigned long rate, u8 *divp, u8 *pre_divp,
+				 u8 parent, unsigned long parent_rate)
+{
+	u8 div, calcp, calcm = 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 pll6 */
+	if (parent == SUN6I_AHB1_MUX_PARENT_PLL6) {
+		if (div < 4)
+			calcp = 0;
+		else if (div / 2 < 4)
+			calcp = 1;
+		else if (div / 4 < 4)
+			calcp = 2;
+		else
+			calcp = 3;
+
+		calcm = DIV_ROUND_UP(div, 1 << calcp);
+	} else {
+		calcp = __roundup_pow_of_two(div);
+		calcp = calcp > 3 ? 3 : calcp;
+	}
+
+	/* we were asked to pass back divider values */
+	if (divp) {
+		*divp = calcp;
+		*pre_divp = calcm - 1;
+	}
+
+	return (parent_rate / calcm) >> calcp;
+}
+
+static long sun6i_ahb1_clk_determine_rate(struct clk_hw *hw, unsigned long rate,
+					  unsigned long *best_parent_rate,
+					  struct clk_hw **best_parent_clk)
+{
+	struct clk *clk = hw->clk, *parent, *best_parent = NULL;
+	int i, num_parents;
+	unsigned long parent_rate, best = 0, child_rate, best_child_rate = 0;
+
+	/* find the parent that can help provide the fastest rate <= rate */
+	num_parents = __clk_get_num_parents(clk);
+	for (i = 0; i < num_parents; i++) {
+		parent = clk_get_parent_by_index(clk, i);
+		if (!parent)
+			continue;
+		if (__clk_get_flags(clk) & CLK_SET_RATE_PARENT)
+			parent_rate = __clk_round_rate(parent, rate);
+		else
+			parent_rate = __clk_get_rate(parent);
+
+		child_rate = sun6i_ahb1_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)
+		*best_parent_clk = __clk_get_hw(best_parent);
+	*best_parent_rate = best;
+
+	return best_child_rate;
+}
+
+static int sun6i_ahb1_clk_set_rate(struct clk_hw *hw, unsigned long rate,
+				   unsigned long parent_rate)
+{
+	struct sun6i_ahb1_clk *ahb1 = to_sun6i_ahb1_clk(hw);
+	unsigned long flags;
+	u8 div, pre_div, parent;
+	u32 reg;
+
+	spin_lock_irqsave(&clk_lock, flags);
+
+	reg = readl(ahb1->reg);
+
+	/* need to know which parent is used to apply pre-divider */
+	parent = SUN6I_AHB1_MUX_GET_PARENT(reg);
+	sun6i_ahb1_clk_round(rate, &div, &pre_div, parent, parent_rate);
+
+	reg = SUN6I_AHB1_DIV_SET(reg, div);
+	reg = SUN6I_AHB1_PLL6_DIV_SET(reg, pre_div);
+	writel(reg, ahb1->reg);
+
+	spin_unlock_irqrestore(&clk_lock, flags);
+
+	return 0;
+}
+
+static const struct clk_ops sun6i_ahb1_clk_ops = {
+	.determine_rate	= sun6i_ahb1_clk_determine_rate,
+	.recalc_rate	= sun6i_ahb1_clk_recalc_rate,
+	.set_rate	= sun6i_ahb1_clk_set_rate,
+};
+
+static void __init sun6i_ahb1_clk_setup(struct device_node *node)
+{
+	struct clk *clk;
+	struct sun6i_ahb1_clk *ahb1;
+	struct clk_mux *mux;
+	const char *clk_name = node->name;
+	const char *parents[SUN6I_AHB1_MAX_PARENTS];
+	void __iomem *reg;
+	int i = 0;
+
+	reg = of_io_request_and_map(node, 0, of_node_full_name(node));
+
+	/* we have a mux, we will have >1 parents */
+	while (i < SUN6I_AHB1_MAX_PARENTS &&
+	       (parents[i] = of_clk_get_parent_name(node, i)) != NULL)
+		i++;
+
+	of_property_read_string(node, "clock-output-names", &clk_name);
+
+	ahb1 = kzalloc(sizeof(struct sun6i_ahb1_clk), GFP_KERNEL);
+	if (!ahb1)
+		return;
+
+	mux = kzalloc(sizeof(struct clk_mux), GFP_KERNEL);
+	if (!mux) {
+		kfree(ahb1);
+		return;
+	}
+
+	/* set up clock properties */
+	mux->reg = reg;
+	mux->shift = SUN6I_AHB1_MUX_SHIFT;
+	mux->mask = SUN6I_AHB1_MUX_MASK;
+	mux->lock = &clk_lock;
+	ahb1->reg = reg;
+
+	clk = clk_register_composite(NULL, clk_name, parents, i,
+				     &mux->hw, &clk_mux_ops,
+				     &ahb1->hw, &sun6i_ahb1_clk_ops,
+				     NULL, NULL, 0);
+
+	if (!IS_ERR(clk)) {
+		of_clk_add_provider(node, of_clk_src_simple_get, clk);
+		clk_register_clkdev(clk, clk_name, NULL);
+	}
+}
+CLK_OF_DECLARE(sun6i_a31_ahb1, "allwinner,sun6i-a31-ahb1-clk", sun6i_ahb1_clk_setup);
+
 /* Maximum number of parents our clocks have */
 #define SUNXI_MAX_PARENTS	5