ARM: OMAP2: Clock: Add OMAP3 DPLL autoidle functions

This patch adds support for DPLL autoidle control to the OMAP3 clock
framework.  These functions will be used by the noncore DPLL enable
and disable code - this is because, according to the CDP code, the
DPLL autoidle status must be saved and restored across DPLL
lock/bypass/off transitions.

N.B.: the CORE DPLL (DPLL3) has three autoidle mode options, rather
than just two.  This code currently does not support the third option,
low-power bypass autoidle.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/mach-omap2/clock34xx.c

@@ -1,10 +1,11 @@
 /*
  * OMAP3-specific clock framework functions
  *
- * Copyright (C) 2007 Texas Instruments, Inc.
- * Copyright (C) 2007 Nokia Corporation
+ * Copyright (C) 2007-2008 Texas Instruments, Inc.
+ * Copyright (C) 2007-2008 Nokia Corporation
  *
  * Written by Paul Walmsley
+ * Testing and integration fixes by Jouni Högander
  *
  * Parts of this code are based on code written by
  * Richard Woodruff, Tony Lindgren, Tuukka Tikkanen, Karthik Dasu
@@ -23,6 +24,7 @@
 #include <linux/delay.h>
 #include <linux/clk.h>
 #include <linux/io.h>
+#include <linux/limits.h>
 
 #include <asm/arch/clock.h>
 #include <asm/arch/sram.h>
@@ -37,8 +39,11 @@
 #include "cm.h"
 #include "cm-regbits-34xx.h"
 
-/* CM_CLKEN_PLL*.EN* bit values */
-#define DPLL_LOCKED		0x7
+/* CM_AUTOIDLE_PLL*.AUTO_* bit values */
+#define DPLL_AUTOIDLE_DISABLE			0x0
+#define DPLL_AUTOIDLE_LOW_POWER_STOP		0x1
+
+#define MAX_DPLL_WAIT_TRIES		1000000
 
 /**
  * omap3_dpll_recalc - recalculate DPLL rate
@@ -53,6 +58,290 @@ static void omap3_dpll_recalc(struct clk *clk)
 	propagate_rate(clk);
 }
 
+/* _omap3_dpll_write_clken - write clken_bits arg to a DPLL's enable bits */
+static void _omap3_dpll_write_clken(struct clk *clk, u8 clken_bits)
+{
+	const struct dpll_data *dd;
+
+	dd = clk->dpll_data;
+
+	cm_rmw_reg_bits(dd->enable_mask, clken_bits << __ffs(dd->enable_mask),
+			dd->control_reg);
+}
+
+/* _omap3_wait_dpll_status: wait for a DPLL to enter a specific state */
+static int _omap3_wait_dpll_status(struct clk *clk, u8 state)
+{
+	const struct dpll_data *dd;
+	int i = 0;
+	int ret = -EINVAL;
+	u32 idlest_mask;
+
+	dd = clk->dpll_data;
+
+	state <<= dd->idlest_bit;
+	idlest_mask = 1 << dd->idlest_bit;
+
+	while (((cm_read_reg(dd->idlest_reg) & idlest_mask) != state) &&
+	       i < MAX_DPLL_WAIT_TRIES) {
+		i++;
+		udelay(1);
+	}
+
+	if (i == MAX_DPLL_WAIT_TRIES) {
+		printk(KERN_ERR "clock: %s failed transition to '%s'\n",
+		       clk->name, (state) ? "locked" : "bypassed");
+	} else {
+		pr_debug("clock: %s transition to '%s' in %d loops\n",
+			 clk->name, (state) ? "locked" : "bypassed", i);
+
+		ret = 0;
+	}
+
+	return ret;
+}
+
+/* Non-CORE DPLL (e.g., DPLLs that do not control SDRC) clock functions */
+
+/*
+ * _omap3_noncore_dpll_lock - instruct a DPLL to lock and wait for readiness
+ * @clk: pointer to a DPLL struct clk
+ *
+ * Instructs a non-CORE DPLL to lock.  Waits for the DPLL to report
+ * readiness before returning.  Will save and restore the DPLL's
+ * autoidle state across the enable, per the CDP code.  If the DPLL
+ * locked successfully, return 0; if the DPLL did not lock in the time
+ * allotted, or DPLL3 was passed in, return -EINVAL.
+ */
+static int _omap3_noncore_dpll_lock(struct clk *clk)
+{
+	u8 ai;
+	int r;
+
+	if (clk == &dpll3_ck)
+		return -EINVAL;
+
+	pr_debug("clock: locking DPLL %s\n", clk->name);
+
+	ai = omap3_dpll_autoidle_read(clk);
+
+	_omap3_dpll_write_clken(clk, DPLL_LOCKED);
+
+	if (ai) {
+		/*
+		 * If no downstream clocks are enabled, CM_IDLEST bit
+		 * may never become active, so don't wait for DPLL to lock.
+		 */
+		r = 0;
+		omap3_dpll_allow_idle(clk);
+	} else {
+		r = _omap3_wait_dpll_status(clk, 1);
+		omap3_dpll_deny_idle(clk);
+	};
+
+	return r;
+}
+
+/*
+ * omap3_noncore_dpll_bypass - instruct a DPLL to bypass and wait for readiness
+ * @clk: pointer to a DPLL struct clk
+ *
+ * Instructs a non-CORE DPLL to enter low-power bypass mode.  In
+ * bypass mode, the DPLL's rate is set equal to its parent clock's
+ * rate.  Waits for the DPLL to report readiness before returning.
+ * Will save and restore the DPLL's autoidle state across the enable,
+ * per the CDP code.  If the DPLL entered bypass mode successfully,
+ * return 0; if the DPLL did not enter bypass in the time allotted, or
+ * DPLL3 was passed in, or the DPLL does not support low-power bypass,
+ * return -EINVAL.
+ */
+static int _omap3_noncore_dpll_bypass(struct clk *clk)
+{
+	int r;
+	u8 ai;
+
+	if (clk == &dpll3_ck)
+		return -EINVAL;
+
+	if (!(clk->dpll_data->modes & (1 << DPLL_LOW_POWER_BYPASS)))
+		return -EINVAL;
+
+	pr_debug("clock: configuring DPLL %s for low-power bypass\n",
+		 clk->name);
+
+	ai = omap3_dpll_autoidle_read(clk);
+
+	_omap3_dpll_write_clken(clk, DPLL_LOW_POWER_BYPASS);
+
+	r = _omap3_wait_dpll_status(clk, 0);
+
+	if (ai)
+		omap3_dpll_allow_idle(clk);
+	else
+		omap3_dpll_deny_idle(clk);
+
+	return r;
+}
+
+/*
+ * _omap3_noncore_dpll_stop - instruct a DPLL to stop
+ * @clk: pointer to a DPLL struct clk
+ *
+ * Instructs a non-CORE DPLL to enter low-power stop. Will save and
+ * restore the DPLL's autoidle state across the stop, per the CDP
+ * code.  If DPLL3 was passed in, or the DPLL does not support
+ * low-power stop, return -EINVAL; otherwise, return 0.
+ */
+static int _omap3_noncore_dpll_stop(struct clk *clk)
+{
+	u8 ai;
+
+	if (clk == &dpll3_ck)
+		return -EINVAL;
+
+	if (!(clk->dpll_data->modes & (1 << DPLL_LOW_POWER_STOP)))
+		return -EINVAL;
+
+	pr_debug("clock: stopping DPLL %s\n", clk->name);
+
+	ai = omap3_dpll_autoidle_read(clk);
+
+	_omap3_dpll_write_clken(clk, DPLL_LOW_POWER_STOP);
+
+	if (ai)
+		omap3_dpll_allow_idle(clk);
+	else
+		omap3_dpll_deny_idle(clk);
+
+	return 0;
+}
+
+/**
+ * omap3_noncore_dpll_enable - instruct a DPLL to enter bypass or lock mode
+ * @clk: pointer to a DPLL struct clk
+ *
+ * Instructs a non-CORE DPLL to enable, e.g., to enter bypass or lock.
+ * The choice of modes depends on the DPLL's programmed rate: if it is
+ * the same as the DPLL's parent clock, it will enter bypass;
+ * otherwise, it will enter lock.  This code will wait for the DPLL to
+ * indicate readiness before returning, unless the DPLL takes too long
+ * to enter the target state.  Intended to be used as the struct clk's
+ * enable function.  If DPLL3 was passed in, or the DPLL does not
+ * support low-power stop, or if the DPLL took too long to enter
+ * bypass or lock, return -EINVAL; otherwise, return 0.
+ */
+static int omap3_noncore_dpll_enable(struct clk *clk)
+{
+	int r;
+
+	if (clk == &dpll3_ck)
+		return -EINVAL;
+
+	if (clk->parent->rate == clk_get_rate(clk))
+		r = _omap3_noncore_dpll_bypass(clk);
+	else
+		r = _omap3_noncore_dpll_lock(clk);
+
+	return r;
+}
+
+/**
+ * omap3_noncore_dpll_enable - instruct a DPLL to enter bypass or lock mode
+ * @clk: pointer to a DPLL struct clk
+ *
+ * Instructs a non-CORE DPLL to enable, e.g., to enter bypass or lock.
+ * The choice of modes depends on the DPLL's programmed rate: if it is
+ * the same as the DPLL's parent clock, it will enter bypass;
+ * otherwise, it will enter lock.  This code will wait for the DPLL to
+ * indicate readiness before returning, unless the DPLL takes too long
+ * to enter the target state.  Intended to be used as the struct clk's
+ * enable function.  If DPLL3 was passed in, or the DPLL does not
+ * support low-power stop, or if the DPLL took too long to enter
+ * bypass or lock, return -EINVAL; otherwise, return 0.
+ */
+static void omap3_noncore_dpll_disable(struct clk *clk)
+{
+	if (clk == &dpll3_ck)
+		return;
+
+	_omap3_noncore_dpll_stop(clk);
+}
+
+/**
+ * omap3_dpll_autoidle_read - read a DPLL's autoidle bits
+ * @clk: struct clk * of the DPLL to read
+ *
+ * Return the DPLL's autoidle bits, shifted down to bit 0.  Returns
+ * -EINVAL if passed a null pointer or if the struct clk does not
+ * appear to refer to a DPLL.
+ */
+static u32 omap3_dpll_autoidle_read(struct clk *clk)
+{
+	const struct dpll_data *dd;
+	u32 v;
+
+	if (!clk || !clk->dpll_data)
+		return -EINVAL;
+
+	dd = clk->dpll_data;
+
+	v = cm_read_reg(dd->autoidle_reg);
+	v &= dd->autoidle_mask;
+	v >>= __ffs(dd->autoidle_mask);
+
+	return v;
+}
+
+/**
+ * omap3_dpll_allow_idle - enable DPLL autoidle bits
+ * @clk: struct clk * of the DPLL to operate on
+ *
+ * Enable DPLL automatic idle control.  This automatic idle mode
+ * switching takes effect only when the DPLL is locked, at least on
+ * OMAP3430.  The DPLL will enter low-power stop when its downstream
+ * clocks are gated.  No return value.
+ */
+static void omap3_dpll_allow_idle(struct clk *clk)
+{
+	const struct dpll_data *dd;
+
+	if (!clk || !clk->dpll_data)
+		return;
+
+	dd = clk->dpll_data;
+
+	/*
+	 * REVISIT: CORE DPLL can optionally enter low-power bypass
+	 * by writing 0x5 instead of 0x1.  Add some mechanism to
+	 * optionally enter this mode.
+	 */
+	cm_rmw_reg_bits(dd->autoidle_mask,
+			DPLL_AUTOIDLE_LOW_POWER_STOP << __ffs(dd->autoidle_mask),
+			dd->autoidle_reg);
+}
+
+/**
+ * omap3_dpll_deny_idle - prevent DPLL from automatically idling
+ * @clk: struct clk * of the DPLL to operate on
+ *
+ * Disable DPLL automatic idle control.  No return value.
+ */
+static void omap3_dpll_deny_idle(struct clk *clk)
+{
+	const struct dpll_data *dd;
+
+	if (!clk || !clk->dpll_data)
+		return;
+
+	dd = clk->dpll_data;
+
+	cm_rmw_reg_bits(dd->autoidle_mask,
+			DPLL_AUTOIDLE_DISABLE << __ffs(dd->autoidle_mask),
+			dd->autoidle_reg);
+}
+
+/* Clock control for DPLL outputs */
+
 /**
  * omap3_clkoutx2_recalc - recalculate DPLL X2 output virtual clock rate
  * @clk: DPLL output struct clk
@@ -89,6 +378,8 @@ static void omap3_clkoutx2_recalc(struct clk *clk)
 		propagate_rate(clk);
 }
 
+/* Common clock code */
+
 /*
  * As it is structured now, this will prevent an OMAP2/3 multiboot
  * kernel from compiling.  This will need further attention.