---

yaml
---
r: 100800
b: refs/heads/master
c: 88b8ba9
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 542313cc98e72d026d2df86f515699dfaface460
+refs/heads/master: 88b8ba90570067178d32c654ad95786041e86e86

trunk/arch/arm/mach-omap2/clock.c

@@ -41,6 +41,24 @@
 
 #define MAX_CLOCK_ENABLE_WAIT		100000
 
+/* DPLL rate rounding: minimum DPLL multiplier, divider values */
+#define DPLL_MIN_MULTIPLIER		1
+#define DPLL_MIN_DIVIDER		1
+
+/* Possible error results from _dpll_test_mult */
+#define DPLL_MULT_UNDERFLOW		(1 << 0)
+
+/*
+ * Scale factor to mitigate roundoff errors in DPLL rate rounding.
+ * The higher the scale factor, the greater the risk of arithmetic overflow,
+ * but the closer the rounded rate to the target rate.  DPLL_SCALE_FACTOR
+ * must be a power of DPLL_SCALE_BASE.
+ */
+#define DPLL_SCALE_FACTOR		64
+#define DPLL_SCALE_BASE			2
+#define DPLL_ROUNDING_VAL		((DPLL_SCALE_BASE / 2) * \
+					 (DPLL_SCALE_FACTOR / DPLL_SCALE_BASE))
+
 u8 cpu_mask;
 
 /*-------------------------------------------------------------------------
@@ -95,7 +113,7 @@ u32 omap2_get_dpll_rate(struct clk *clk)
 {
 	long long dpll_clk;
 	u32 dpll_mult, dpll_div, dpll;
-	const struct dpll_data *dd;
+	struct dpll_data *dd;
 
 	dd = clk->dpll_data;
 	/* REVISIT: What do we return on error? */
@@ -724,6 +742,184 @@ int omap2_clk_set_parent(struct clk *clk, struct clk *new_parent)
 	return 0;
 }
 
+/* DPLL rate rounding code */
+
+/**
+ * omap2_dpll_set_rate_tolerance: set the error tolerance during rate rounding
+ * @clk: struct clk * of the DPLL
+ * @tolerance: maximum rate error tolerance
+ *
+ * Set the maximum DPLL rate error tolerance for the rate rounding
+ * algorithm.  The rate tolerance is an attempt to balance DPLL power
+ * saving (the least divider value "n") vs. rate fidelity (the least
+ * difference between the desired DPLL target rate and the rounded
+ * rate out of the algorithm).  So, increasing the tolerance is likely
+ * to decrease DPLL power consumption and increase DPLL rate error.
+ * Returns -EINVAL if provided a null clock ptr or a clk that is not a
+ * DPLL; or 0 upon success.
+ */
+int omap2_dpll_set_rate_tolerance(struct clk *clk, unsigned int tolerance)
+{
+	if (!clk || !clk->dpll_data)
+		return -EINVAL;
+
+	clk->dpll_data->rate_tolerance = tolerance;
+
+	return 0;
+}
+
+static unsigned long _dpll_compute_new_rate(unsigned long parent_rate, unsigned int m, unsigned int n)
+{
+	unsigned long long num;
+
+	num = (unsigned long long)parent_rate * m;
+	do_div(num, n);
+	return num;
+}
+
+/*
+ * _dpll_test_mult - test a DPLL multiplier value
+ * @m: pointer to the DPLL m (multiplier) value under test
+ * @n: current DPLL n (divider) value under test
+ * @new_rate: pointer to storage for the resulting rounded rate
+ * @target_rate: the desired DPLL rate
+ * @parent_rate: the DPLL's parent clock rate
+ *
+ * This code tests a DPLL multiplier value, ensuring that the
+ * resulting rate will not be higher than the target_rate, and that
+ * the multiplier value itself is valid for the DPLL.  Initially, the
+ * integer pointed to by the m argument should be prescaled by
+ * multiplying by DPLL_SCALE_FACTOR.  The code will replace this with
+ * a non-scaled m upon return.  This non-scaled m will result in a
+ * new_rate as close as possible to target_rate (but not greater than
+ * target_rate) given the current (parent_rate, n, prescaled m)
+ * triple. Returns DPLL_MULT_UNDERFLOW in the event that the
+ * non-scaled m attempted to underflow, which can allow the calling
+ * function to bail out early; or 0 upon success.
+ */
+static int _dpll_test_mult(int *m, int n, unsigned long *new_rate,
+			   unsigned long target_rate,
+			   unsigned long parent_rate)
+{
+	int flags = 0, carry = 0;
+
+	/* Unscale m and round if necessary */
+	if (*m % DPLL_SCALE_FACTOR >= DPLL_ROUNDING_VAL)
+		carry = 1;
+	*m = (*m / DPLL_SCALE_FACTOR) + carry;
+
+	/*
+	 * The new rate must be <= the target rate to avoid programming
+	 * a rate that is impossible for the hardware to handle
+	 */
+	*new_rate = _dpll_compute_new_rate(parent_rate, *m, n);
+	if (*new_rate > target_rate) {
+		(*m)--;
+		*new_rate = 0;
+	}
+
+	/* Guard against m underflow */
+	if (*m < DPLL_MIN_MULTIPLIER) {
+		*m = DPLL_MIN_MULTIPLIER;
+		*new_rate = 0;
+		flags = DPLL_MULT_UNDERFLOW;
+	}
+
+	if (*new_rate == 0)
+		*new_rate = _dpll_compute_new_rate(parent_rate, *m, n);
+
+	return flags;
+}
+
+/**
+ * omap2_dpll_round_rate - round a target rate for an OMAP DPLL
+ * @clk: struct clk * for a DPLL
+ * @target_rate: desired DPLL clock rate
+ *
+ * Given a DPLL, a desired target rate, and a rate tolerance, round
+ * the target rate to a possible, programmable rate for this DPLL.
+ * Rate tolerance is assumed to be set by the caller before this
+ * function is called.  Attempts to select the minimum possible n
+ * within the tolerance to reduce power consumption.  Stores the
+ * computed (m, n) in the DPLL's dpll_data structure so set_rate()
+ * will not need to call this (expensive) function again.  Returns ~0
+ * if the target rate cannot be rounded, either because the rate is
+ * too low or because the rate tolerance is set too tightly; or the
+ * rounded rate upon success.
+ */
+long omap2_dpll_round_rate(struct clk *clk, unsigned long target_rate)
+{
+	int m, n, r, e, scaled_max_m;
+	unsigned long scaled_rt_rp, new_rate;
+	int min_e = -1, min_e_m = -1, min_e_n = -1;
+
+	if (!clk || !clk->dpll_data)
+		return ~0;
+
+	pr_debug("clock: starting DPLL round_rate for clock %s, target rate "
+		 "%ld\n", clk->name, target_rate);
+
+	scaled_rt_rp = target_rate / (clk->parent->rate / DPLL_SCALE_FACTOR);
+	scaled_max_m = clk->dpll_data->max_multiplier * DPLL_SCALE_FACTOR;
+
+	clk->dpll_data->last_rounded_rate = 0;
+
+	for (n = clk->dpll_data->max_divider; n >= DPLL_MIN_DIVIDER; n--) {
+
+		/* Compute the scaled DPLL multiplier, based on the divider */
+		m = scaled_rt_rp * n;
+
+		/*
+		 * Since we're counting n down, a m overflow means we can
+		 * can immediately skip to the next n
+		 */
+		if (m > scaled_max_m)
+			continue;
+
+		r = _dpll_test_mult(&m, n, &new_rate, target_rate,
+				    clk->parent->rate);
+
+		e = target_rate - new_rate;
+		pr_debug("clock: n = %d: m = %d: rate error is %d "
+			 "(new_rate = %ld)\n", n, m, e, new_rate);
+
+		if (min_e == -1 ||
+		    min_e >= (int)(abs(e) - clk->dpll_data->rate_tolerance)) {
+			min_e = e;
+			min_e_m = m;
+			min_e_n = n;
+
+			pr_debug("clock: found new least error %d\n", min_e);
+		}
+
+		/*
+		 * Since we're counting n down, a m underflow means we
+		 * can bail out completely (since as n decreases in
+		 * the next iteration, there's no way that m can
+		 * increase beyond the current m)
+		 */
+		if (r & DPLL_MULT_UNDERFLOW)
+			break;
+	}
+
+	if (min_e < 0) {
+		pr_debug("clock: error: target rate or tolerance too low\n");
+		return ~0;
+	}
+
+	clk->dpll_data->last_rounded_m = min_e_m;
+	clk->dpll_data->last_rounded_n = min_e_n;
+	clk->dpll_data->last_rounded_rate =
+		_dpll_compute_new_rate(clk->parent->rate, min_e_m,  min_e_n);
+
+	pr_debug("clock: final least error: e = %d, m = %d, n = %d\n",
+		 min_e, min_e_m, min_e_n);
+	pr_debug("clock: final rate: %ld  (target rate: %ld)\n",
+		 clk->dpll_data->last_rounded_rate, target_rate);
+
+	return clk->dpll_data->last_rounded_rate;
+}
+
 /*-------------------------------------------------------------------------
  * Omap2 clock reset and init functions
  *-------------------------------------------------------------------------*/

trunk/arch/arm/mach-omap2/clock.h

@@ -18,11 +18,16 @@
 
 #include <asm/arch/clock.h>
 
+/* The maximum error between a target DPLL rate and the rounded rate in Hz */
+#define DEFAULT_DPLL_RATE_TOLERANCE	50000
+
 int omap2_clk_enable(struct clk *clk);
 void omap2_clk_disable(struct clk *clk);
 long omap2_clk_round_rate(struct clk *clk, unsigned long rate);
 int omap2_clk_set_rate(struct clk *clk, unsigned long rate);
 int omap2_clk_set_parent(struct clk *clk, struct clk *new_parent);
+int omap2_dpll_rate_tolerance_set(struct clk *clk, unsigned int tolerance);
+long omap2_dpll_round_rate(struct clk *clk, unsigned long target_rate);
 
 #ifdef CONFIG_OMAP_RESET_CLOCKS
 void omap2_clk_disable_unused(struct clk *clk);

trunk/arch/arm/mach-omap2/clock24xx.c

@@ -154,7 +154,7 @@ static void omap2_clk_fixed_disable(struct clk *clk)
  * Uses the current prcm set to tell if a rate is valid.
  * You can go slower, but not faster within a given rate set.
  */
-static u32 omap2_dpll_round_rate(unsigned long target_rate)
+long omap2_dpllcore_round_rate(unsigned long target_rate)
 {
 	u32 high, low, core_clk_src;
 
@@ -183,14 +183,14 @@ static u32 omap2_dpll_round_rate(unsigned long target_rate)
 
 }
 
-static void omap2_dpll_recalc(struct clk *clk)
+static void omap2_dpllcore_recalc(struct clk *clk)
 {
 	clk->rate = omap2_get_dpll_rate_24xx(clk);
 
 	propagate_rate(clk);
 }
 
-static int omap2_reprogram_dpll(struct clk *clk, unsigned long rate)
+static int omap2_reprogram_dpllcore(struct clk *clk, unsigned long rate)
 {
 	u32 cur_rate, low, mult, div, valid_rate, done_rate;
 	u32 bypass = 0;
@@ -209,7 +209,7 @@ static int omap2_reprogram_dpll(struct clk *clk, unsigned long rate)
 	} else if ((rate == (cur_rate * 2)) && (mult == 1)) {
 		omap2_reprogram_sdrc(CORE_CLK_SRC_DPLL_X2, 1);
 	} else if (rate != cur_rate) {
-		valid_rate = omap2_dpll_round_rate(rate);
+		valid_rate = omap2_dpllcore_round_rate(rate);
 		if (valid_rate != rate)
 			goto dpll_exit;
 
@@ -256,7 +256,7 @@ static int omap2_reprogram_dpll(struct clk *clk, unsigned long rate)
 		omap2_init_memory_params(omap2_dll_force_needed());
 		omap2_reprogram_sdrc(done_rate, 0);
 	}
-	omap2_dpll_recalc(&dpll_ck);
+	omap2_dpllcore_recalc(&dpll_ck);
 	ret = 0;
 
 dpll_exit:
@@ -383,7 +383,7 @@ static int omap2_select_table_rate(struct clk *clk, unsigned long rate)
 
 		local_irq_restore(flags);
 	}
-	omap2_dpll_recalc(&dpll_ck);
+	omap2_dpllcore_recalc(&dpll_ck);
 
 	return 0;
 }

trunk/arch/arm/mach-omap2/clock24xx.h

@@ -30,12 +30,12 @@ static long omap2_round_to_table_rate(struct clk *clk, unsigned long rate);
 static void omap2_sys_clk_recalc(struct clk *clk);
 static void omap2_osc_clk_recalc(struct clk *clk);
 static void omap2_sys_clk_recalc(struct clk *clk);
-static void omap2_dpll_recalc(struct clk *clk);
+static void omap2_dpllcore_recalc(struct clk *clk);
 static int omap2_clk_fixed_enable(struct clk *clk);
 static void omap2_clk_fixed_disable(struct clk *clk);
 static int omap2_enable_osc_ck(struct clk *clk);
 static void omap2_disable_osc_ck(struct clk *clk);
-static int omap2_reprogram_dpll(struct clk *clk, unsigned long rate);
+static int omap2_reprogram_dpllcore(struct clk *clk, unsigned long rate);
 
 /* Key dividers which make up a PRCM set. Ratio's for a PRCM are mandated.
  * xtal_speed, dpll_speed, mpu_speed, CM_CLKSEL_MPU,CM_CLKSEL_DSP
@@ -665,20 +665,27 @@ static struct clk alt_ck = {		/* Typical 54M or 48M, may not exist */
  * deal with this
  */
 
-static const struct dpll_data dpll_dd = {
+static struct dpll_data dpll_dd = {
 	.mult_div1_reg		= OMAP_CM_REGADDR(PLL_MOD, CM_CLKSEL1),
 	.mult_mask		= OMAP24XX_DPLL_MULT_MASK,
 	.div1_mask		= OMAP24XX_DPLL_DIV_MASK,
+	.max_multiplier		= 1024,
+	.max_divider		= 16,
+	.rate_tolerance		= DEFAULT_DPLL_RATE_TOLERANCE
 };
 
+/*
+ * XXX Cannot add round_rate here yet, as this is still a composite clock,
+ * not just a DPLL
+ */
 static struct clk dpll_ck = {
 	.name		= "dpll_ck",
 	.parent		= &sys_ck,		/* Can be func_32k also */
 	.dpll_data	= &dpll_dd,
 	.flags		= CLOCK_IN_OMAP242X | CLOCK_IN_OMAP243X |
 				RATE_PROPAGATES | ALWAYS_ENABLED,
-	.recalc		= &omap2_dpll_recalc,
-	.set_rate	= &omap2_reprogram_dpll,
+	.recalc		= &omap2_dpllcore_recalc,
+	.set_rate	= &omap2_reprogram_dpllcore,
 };
 
 static struct clk apll96_ck = {