OMAP2+ clock: clean up clkt_clksel.c

This patch cleans up arch/arm/mach-omap2/clkt_clksel.c.  It:

- makes several functions static that are not called outside the file;

- adds documentation;

- makes some code paths easier to read (hopefully), by breaking up
  compound statements and removing redundant checks;

- converts some pr_err()s that indicate clock tree data problems into WARN()s,
  so they are more likely to be noticed;

- and moves omap2_clk_round_rate() back into mach-omap2/clock.c, its proper
  home, since it is not clksel-specific.

Signed-off-by: Paul Walmsley <paul@pwsan.com>

1 files changed, 251 insertions, 172 deletions

diff --git a/arch/arm/mach-omap2/clkt_clksel.c b/arch/arm/mach-omap2/clkt_clksel.c
index 9a23aebeea7e..a781cd6795a4 100644
--- a/arch/arm/mach-omap2/clkt_clksel.c
+++ b/arch/arm/mach-omap2/clkt_clksel.c
@@ -12,8 +12,26 @@
  * it under the terms of the GNU General Public License version 2 as
  * published by the Free Software Foundation.
  *
- * XXX At some point these clksel clocks should be split into
- * "divider" clocks and "mux" clocks to better match the hardware.
+ *
+ * clksel clocks are clocks that do not have a fixed parent, or that
+ * can divide their parent's rate, or possibly both at the same time, based
+ * on the contents of a hardware register bitfield.
+ *
+ * All of the various mux and divider settings can be encoded into
+ * struct clksel* data structures, and then these can be autogenerated
+ * from some hardware database for each new chip generation.  This
+ * should avoid the need to write, review, and validate a lot of new
+ * clock code for each new chip, since it can be exported from the SoC
+ * design flow.  This is now done on OMAP4.
+ *
+ * The fusion of mux and divider clocks is a software creation.  In
+ * hardware reality, the multiplexer (parent selection) and the
+ * divider exist separately.  XXX At some point these clksel clocks
+ * should be split into "divider" clocks and "mux" clocks to better
+ * match the hardware.
+ *
+ * (The name "clksel" comes from the name of the corresponding
+ * register field in the OMAP2/3 family of SoCs.)
  *
  * XXX Currently these clocks are only used in the OMAP2/3/4 code, but
  * many of the OMAP1 clocks should be convertible to use this
@@ -29,14 +47,11 @@
 #include <plat/clock.h>
 
 #include "clock.h"
-#include "cm.h"
-#include "cm-regbits-24xx.h"
-#include "cm-regbits-34xx.h"
 
 /* Private functions */
 
 /**
- * _omap2_get_clksel_by_parent - return clksel struct for a given clk & parent
+ * _get_clksel_by_parent() - return clksel struct for a given clk & parent
  * @clk: OMAP struct clk ptr to inspect
  * @src_clk: OMAP struct clk ptr of the parent clk to search for
  *
@@ -44,23 +59,19 @@
  * the element associated with the supplied parent clock address.
  * Returns a pointer to the struct clksel on success or NULL on error.
  */
-static const struct clksel *_omap2_get_clksel_by_parent(struct clk *clk,
-							struct clk *src_clk)
+static const struct clksel *_get_clksel_by_parent(struct clk *clk,
+						  struct clk *src_clk)
 {
 	const struct clksel *clks;
 
-	if (!clk->clksel)
-		return NULL;
-
-	for (clks = clk->clksel; clks->parent; clks++) {
+	for (clks = clk->clksel; clks->parent; clks++)
 		if (clks->parent == src_clk)
 			break; /* Found the requested parent */
-	}
 
 	if (!clks->parent) {
-		printk(KERN_ERR "clock: Could not find parent clock %s in "
-		       "clksel array of clock %s\n", src_clk->name,
-		       clk->name);
+		/* This indicates a data problem */
+		WARN(1, "clock: Could not find parent clock %s in clksel array "
+		     "of clock %s\n", src_clk->name, clk->name);
 		return NULL;
 	}
 
@@ -68,7 +79,7 @@ static const struct clksel *_omap2_get_clksel_by_parent(struct clk *clk,
 }
 
 /**
- * _omap2_clksel_get_src_field - find the new clksel divisor to use
+ * _get_div_and_fieldval() - find the new clksel divisor and field value to use
  * @src_clk: planned new parent struct clk *
  * @clk: struct clk * that is being reparented
  * @field_val: pointer to a u32 to contain the register data for the divisor
@@ -82,14 +93,14 @@ static const struct clksel *_omap2_get_clksel_by_parent(struct clk *clk,
  * success (in this latter case, the corresponding register bitfield
  * value is passed back in the variable pointed to by @field_val)
  */
-static u8 _omap2_clksel_get_src_field(struct clk *src_clk, struct clk *clk,
-				      u32 *field_val)
+static u8 _get_div_and_fieldval(struct clk *src_clk, struct clk *clk,
+				u32 *field_val)
 {
 	const struct clksel *clks;
 	const struct clksel_rate *clkr, *max_clkr;
 	u8 max_div = 0;
 
-	clks = _omap2_get_clksel_by_parent(clk, src_clk);
+	clks = _get_clksel_by_parent(clk, src_clk);
 	if (!clks)
 		return 0;
 
@@ -113,9 +124,9 @@ static u8 _omap2_clksel_get_src_field(struct clk *src_clk, struct clk *clk,
 	}
 
 	if (max_div == 0) {
-		WARN(1, "clock: Could not find divisor for "
-		       "clock %s parent %s\n", clk->name,
-		       src_clk->parent->name);
+		/* This indicates an error in the clksel data */
+		WARN(1, "clock: Could not find divisor for clock %s parent %s"
+		     "\n", clk->name, src_clk->parent->name);
 		return 0;
 	}
 
@@ -124,82 +135,141 @@ static u8 _omap2_clksel_get_src_field(struct clk *src_clk, struct clk *clk,
 	return max_div;
 }
 
+/**
+ * _write_clksel_reg() - program a clock's clksel register in hardware
+ * @clk: struct clk * to program
+ * @v: clksel bitfield value to program (with LSB at bit 0)
+ *
+ * Shift the clksel register bitfield value @v to its appropriate
+ * location in the clksel register and write it in.  This function
+ * will ensure that the write to the clksel_reg reaches its
+ * destination before returning -- important since PRM and CM register
+ * accesses can be quite slow compared to ARM cycles -- but does not
+ * take into account any time the hardware might take to switch the
+ * clock source.
+ */
+static void _write_clksel_reg(struct clk *clk, u32 field_val)
+{
+	u32 v;
 
-/* Public functions */
+	v = __raw_readl(clk->clksel_reg);
+	v &= ~clk->clksel_mask;
+	v |= field_val << __ffs(clk->clksel_mask);
+	__raw_writel(v, clk->clksel_reg);
+
+	v = __raw_readl(clk->clksel_reg); /* OCP barrier */
+}
 
 /**
- * omap2_init_clksel_parent - set a clksel clk's parent field from the hardware
- * @clk: OMAP clock struct ptr to use
+ * _clksel_to_divisor() - turn clksel field value into integer divider
+ * @clk: OMAP struct clk to use
+ * @field_val: register field value to find
  *
- * Given a pointer to a source-selectable struct clk, read the hardware
- * register and determine what its parent is currently set to.  Update the
- * clk->parent field with the appropriate clk ptr.
+ * Given a struct clk of a rate-selectable clksel clock, and a register field
+ * value to search for, find the corresponding clock divisor.  The register
+ * field value should be pre-masked and shifted down so the LSB is at bit 0
+ * before calling.  Returns 0 on error or returns the actual integer divisor
+ * upon success.
  */
-void omap2_init_clksel_parent(struct clk *clk)
+static u32 _clksel_to_divisor(struct clk *clk, u32 field_val)
 {
 	const struct clksel *clks;
 	const struct clksel_rate *clkr;
-	u32 r, found = 0;
 
-	if (!clk->clksel)
-		return;
+	clks = _get_clksel_by_parent(clk, clk->parent);
+	if (!clks)
+		return 0;
 
-	r = __raw_readl(clk->clksel_reg) & clk->clksel_mask;
-	r >>= __ffs(clk->clksel_mask);
+	for (clkr = clks->rates; clkr->div; clkr++) {
+		if (!(clkr->flags & cpu_mask))
+			continue;
 
-	for (clks = clk->clksel; clks->parent && !found; clks++) {
-		for (clkr = clks->rates; clkr->div && !found; clkr++) {
-			if ((clkr->flags & cpu_mask) && (clkr->val == r)) {
-				if (clk->parent != clks->parent) {
-					pr_debug("clock: inited %s parent "
-						 "to %s (was %s)\n",
-						 clk->name, clks->parent->name,
-						 ((clk->parent) ?
-						  clk->parent->name : "NULL"));
-					clk_reparent(clk, clks->parent);
-				};
-				found = 1;
-			}
-		}
+		if (clkr->val == field_val)
+			break;
 	}
 
-	if (!found)
-		printk(KERN_ERR "clock: init parent: could not find "
-		       "regval %0x for clock %s\n", r,  clk->name);
+	if (!clkr->div) {
+		/* This indicates a data error */
+		WARN(1, "clock: Could not find fieldval %d for clock %s parent "
+		     "%s\n", field_val, clk->name, clk->parent->name);
+		return 0;
+	}
 
-	return;
+	return clkr->div;
 }
 
-/*
- * Used for clocks that are part of CLKSEL_xyz governed clocks.
- * REVISIT: Maybe change to use clk->enable() functions like on omap1?
+/**
+ * _divisor_to_clksel() - turn clksel integer divisor into a field value
+ * @clk: OMAP struct clk to use
+ * @div: integer divisor to search for
+ *
+ * Given a struct clk of a rate-selectable clksel clock, and a clock
+ * divisor, find the corresponding register field value.  Returns the
+ * register field value _before_ left-shifting (i.e., LSB is at bit
+ * 0); or returns 0xFFFFFFFF (~0) upon error.
  */
-unsigned long omap2_clksel_recalc(struct clk *clk)
+static u32 _divisor_to_clksel(struct clk *clk, u32 div)
 {
-	unsigned long rate;
-	u32 div = 0;
+	const struct clksel *clks;
+	const struct clksel_rate *clkr;
 
-	pr_debug("clock: recalc'ing clksel clk %s\n", clk->name);
+	/* should never happen */
+	WARN_ON(div == 0);
 
-	div = omap2_clksel_get_divisor(clk);
-	if (div == 0)
-		return clk->rate;
+	clks = _get_clksel_by_parent(clk, clk->parent);
+	if (!clks)
+		return ~0;
 
-	rate = clk->parent->rate / div;
+	for (clkr = clks->rates; clkr->div; clkr++) {
+		if (!(clkr->flags & cpu_mask))
+			continue;
 
-	pr_debug("clock: new clock rate is %ld (div %d)\n", rate, div);
+		if (clkr->div == div)
+			break;
+	}
 
-	return rate;
+	if (!clkr->div) {
+		pr_err("clock: Could not find divisor %d for clock %s parent "
+		       "%s\n", div, clk->name, clk->parent->name);
+		return ~0;
+	}
+
+	return clkr->val;
 }
 
 /**
- * omap2_clksel_round_rate_div - find divisor for the given clock and rate
+ * _read_divisor() - get current divisor applied to parent clock (from hdwr)
+ * @clk: OMAP struct clk to use.
+ *
+ * Read the current divisor register value for @clk that is programmed
+ * into the hardware, convert it into the actual divisor value, and
+ * return it; or return 0 on error.
+ */
+static u32 _read_divisor(struct clk *clk)
+{
+	u32 v;
+
+	if (!clk->clksel || !clk->clksel_mask)
+		return 0;
+
+	v = __raw_readl(clk->clksel_reg);
+	v &= clk->clksel_mask;
+	v >>= __ffs(clk->clksel_mask);
+
+	return _clksel_to_divisor(clk, v);
+}
+
+/* Public functions */
+
+/**
+ * omap2_clksel_round_rate_div() - find divisor for the given clock and rate
  * @clk: OMAP struct clk to use
  * @target_rate: desired clock rate
  * @new_div: ptr to where we should store the divisor
  *
  * Finds 'best' divider value in an array based on the source and target
  * rates.  The divider array must be sorted with smallest divider first.
+ * This function is also used by the DPLL3 M2 divider code.
  *
  * Returns the rounded clock rate or returns 0xffffffff on error.
  */
@@ -211,12 +281,15 @@ u32 omap2_clksel_round_rate_div(struct clk *clk, unsigned long target_rate,
 	const struct clksel_rate *clkr;
 	u32 last_div = 0;
 
+	if (!clk->clksel || !clk->clksel_mask)
+		return ~0;
+
 	pr_debug("clock: clksel_round_rate_div: %s target_rate %ld\n",
 		 clk->name, target_rate);
 
 	*new_div = 1;
 
-	clks = _omap2_get_clksel_by_parent(clk, clk->parent);
+	clks = _get_clksel_by_parent(clk, clk->parent);
 	if (!clks)
 		return ~0;
 
@@ -252,168 +325,174 @@ u32 omap2_clksel_round_rate_div(struct clk *clk, unsigned long target_rate,
 	return clk->parent->rate / clkr->div;
 }
 
-/**
- * omap2_clksel_round_rate - find rounded rate for the given clock and rate
- * @clk: OMAP struct clk to use
- * @target_rate: desired clock rate
- *
- * Compatibility wrapper for OMAP clock framework
- * Finds best target rate based on the source clock and possible dividers.
- * rates. The divider array must be sorted with smallest divider first.
- * Note that this will not work for clocks which are part of CONFIG_PARTICIPANT,
- * they are only settable as part of virtual_prcm set.
- *
- * Returns the rounded clock rate or returns 0xffffffff on error.
+/*
+ * Clocktype interface functions to the OMAP clock code
+ * (i.e., those used in struct clk field function pointers, etc.)
  */
-long omap2_clksel_round_rate(struct clk *clk, unsigned long target_rate)
-{
-	u32 new_div;
-
-	return omap2_clksel_round_rate_div(clk, target_rate, &new_div);
-}
-
-
-/* Given a clock and a rate apply a clock specific rounding function */
-long omap2_clk_round_rate(struct clk *clk, unsigned long rate)
-{
-	if (clk->round_rate)
-		return clk->round_rate(clk, rate);
-
-	return clk->rate;
-}
 
 /**
- * omap2_clksel_to_divisor() - turn clksel field value into integer divider
- * @clk: OMAP struct clk to use
- * @field_val: register field value to find
+ * omap2_init_clksel_parent() - set a clksel clk's parent field from the hdwr
+ * @clk: OMAP clock struct ptr to use
  *
- * Given a struct clk of a rate-selectable clksel clock, and a register field
- * value to search for, find the corresponding clock divisor.  The register
- * field value should be pre-masked and shifted down so the LSB is at bit 0
- * before calling.  Returns 0 on error
+ * Given a pointer @clk to a source-selectable struct clk, read the
+ * hardware register and determine what its parent is currently set
+ * to.  Update @clk's .parent field with the appropriate clk ptr.  No
+ * return value.
  */
-u32 omap2_clksel_to_divisor(struct clk *clk, u32 field_val)
+void omap2_init_clksel_parent(struct clk *clk)
 {
 	const struct clksel *clks;
 	const struct clksel_rate *clkr;
+	u32 r, found = 0;
 
-	clks = _omap2_get_clksel_by_parent(clk, clk->parent);
-	if (!clks)
-		return 0;
+	if (!clk->clksel || !clk->clksel_mask)
+		return;
 
-	for (clkr = clks->rates; clkr->div; clkr++) {
-		if ((clkr->flags & cpu_mask) && (clkr->val == field_val))
-			break;
-	}
+	r = __raw_readl(clk->clksel_reg) & clk->clksel_mask;
+	r >>= __ffs(clk->clksel_mask);
 
-	if (!clkr->div) {
-		printk(KERN_ERR "clock: Could not find fieldval %d for "
-		       "clock %s parent %s\n", field_val, clk->name,
-		       clk->parent->name);
-		return 0;
+	for (clks = clk->clksel; clks->parent && !found; clks++) {
+		for (clkr = clks->rates; clkr->div && !found; clkr++) {
+			if (!(clkr->flags & cpu_mask))
+				continue;
+
+			if (clkr->val == r) {
+				if (clk->parent != clks->parent) {
+					pr_debug("clock: inited %s parent "
+						 "to %s (was %s)\n",
+						 clk->name, clks->parent->name,
+						 ((clk->parent) ?
+						  clk->parent->name : "NULL"));
+					clk_reparent(clk, clks->parent);
+				};
+				found = 1;
+			}
+		}
 	}
 
-	return clkr->div;
+	/* This indicates a data error */
+	WARN(!found, "clock: %s: init parent: could not find regval %0x\n",
+	     clk->name, r);
+
+	return;
 }
 
 /**
- * omap2_divisor_to_clksel() - turn clksel integer divisor into a field value
- * @clk: OMAP struct clk to use
- * @div: integer divisor to search for
+ * omap2_clksel_recalc() - function ptr to pass via struct clk .recalc field
+ * @clk: struct clk *
  *
- * Given a struct clk of a rate-selectable clksel clock, and a clock divisor,
- * find the corresponding register field value.  The return register value is
- * the value before left-shifting.  Returns ~0 on error
+ * This function is intended to be called only by the clock framework.
+ * Each clksel clock should have its struct clk .recalc field set to this
+ * function.  Returns the clock's current rate, based on its parent's rate
+ * and its current divisor setting in the hardware.
  */
-u32 omap2_divisor_to_clksel(struct clk *clk, u32 div)
+unsigned long omap2_clksel_recalc(struct clk *clk)
 {
-	const struct clksel *clks;
-	const struct clksel_rate *clkr;
+	unsigned long rate;
+	u32 div = 0;
 
-	/* should never happen */
-	WARN_ON(div == 0);
+	div = _read_divisor(clk);
+	if (div == 0)
+		return clk->rate;
 
-	clks = _omap2_get_clksel_by_parent(clk, clk->parent);
-	if (!clks)
-		return ~0;
+	rate = clk->parent->rate / div;
 
-	for (clkr = clks->rates; clkr->div; clkr++) {
-		if ((clkr->flags & cpu_mask) && (clkr->div == div))
-			break;
-	}
+	pr_debug("clock: %s: recalc'd rate is %ld (div %d)\n", clk->name,
+		 rate, div);
 
-	if (!clkr->div) {
-		printk(KERN_ERR "clock: Could not find divisor %d for "
-		       "clock %s parent %s\n", div, clk->name,
-		       clk->parent->name);
-		return ~0;
-	}
-
-	return clkr->val;
+	return rate;
 }
 
 /**
- * omap2_clksel_get_divisor - get current divider applied to parent clock.
- * @clk: OMAP struct clk to use.
+ * omap2_clksel_round_rate() - find rounded rate for the given clock and rate
+ * @clk: OMAP struct clk to use
+ * @target_rate: desired clock rate
+ *
+ * This function is intended to be called only by the clock framework.
+ * Finds best target rate based on the source clock and possible dividers.
+ * rates. The divider array must be sorted with smallest divider first.
  *
- * Returns the integer divisor upon success or 0 on error.
+ * Returns the rounded clock rate or returns 0xffffffff on error.
  */
-u32 omap2_clksel_get_divisor(struct clk *clk)
+long omap2_clksel_round_rate(struct clk *clk, unsigned long target_rate)
 {
-	u32 v;
-
-	if (!clk->clksel_mask)
-		return 0;
-
-	v = __raw_readl(clk->clksel_reg) & clk->clksel_mask;
-	v >>= __ffs(clk->clksel_mask);
+	u32 new_div;
 
-	return omap2_clksel_to_divisor(clk, v);
+	return omap2_clksel_round_rate_div(clk, target_rate, &new_div);
 }
 
+/**
+ * omap2_clksel_set_rate() - program clock rate in hardware
+ * @clk: struct clk * to program rate
+ * @rate: target rate to program
+ *
+ * This function is intended to be called only by the clock framework.
+ * Program @clk's rate to @rate in the hardware.  The clock can be
+ * either enabled or disabled when this happens, although if the clock
+ * is enabled, some downstream devices may glitch or behave
+ * unpredictably when the clock rate is changed - this depends on the
+ * hardware. This function does not currently check the usecount of
+ * the clock, so if multiple drivers are using the clock, and the rate
+ * is changed, they will all be affected without any notification.
+ * Returns -EINVAL upon error, or 0 upon success.
+ */
 int omap2_clksel_set_rate(struct clk *clk, unsigned long rate)
 {
-	u32 v, field_val, validrate, new_div = 0;
+	u32 field_val, validrate, new_div = 0;
 
-	if (!clk->clksel_mask)
+	if (!clk->clksel || !clk->clksel_mask)
 		return -EINVAL;
 
 	validrate = omap2_clksel_round_rate_div(clk, rate, &new_div);
 	if (validrate != rate)
 		return -EINVAL;
 
-	field_val = omap2_divisor_to_clksel(clk, new_div);
+	field_val = _divisor_to_clksel(clk, new_div);
 	if (field_val == ~0)
 		return -EINVAL;
 
-	v = __raw_readl(clk->clksel_reg);
-	v &= ~clk->clksel_mask;
-	v |= field_val << __ffs(clk->clksel_mask);
-	__raw_writel(v, clk->clksel_reg);
-	v = __raw_readl(clk->clksel_reg); /* OCP barrier */
+	_write_clksel_reg(clk, field_val);
 
 	clk->rate = clk->parent->rate / new_div;
 
+	pr_debug("clock: %s: set rate to %ld\n", clk->name, clk->rate);
+
 	return 0;
 }
 
+/*
+ * Clksel parent setting function - not passed in struct clk function
+ * pointer - instead, the OMAP clock code currently assumes that any
+ * parent-setting clock is a clksel clock, and calls
+ * omap2_clksel_set_parent() by default
+ */
+
+/**
+ * omap2_clksel_set_parent() - change a clock's parent clock
+ * @clk: struct clk * of the child clock
+ * @new_parent: struct clk * of the new parent clock
+ *
+ * This function is intended to be called only by the clock framework.
+ * Change the parent clock of clock @clk to @new_parent.  This is
+ * intended to be used while @clk is disabled.  This function does not
+ * currently check the usecount of the clock, so if multiple drivers
+ * are using the clock, and the parent is changed, they will all be
+ * affected without any notification.  Returns -EINVAL upon error, or
+ * 0 upon success.
+ */
 int omap2_clksel_set_parent(struct clk *clk, struct clk *new_parent)
 {
-	u32 field_val, v, parent_div;
+	u32 field_val = 0;
+	u32 parent_div;
 
 	if (!clk->clksel || !clk->clksel_mask)
 		return -EINVAL;
 
-	parent_div = _omap2_clksel_get_src_field(new_parent, clk, &field_val);
+	parent_div = _get_div_and_fieldval(new_parent, clk, &field_val);
 	if (!parent_div)
 		return -EINVAL;
 
-	/* Set new source value (previous dividers if any in effect) */
-	v = __raw_readl(clk->clksel_reg);
-	v &= ~clk->clksel_mask;
-	v |= field_val << __ffs(clk->clksel_mask);
-	__raw_writel(v, clk->clksel_reg);
-	v = __raw_readl(clk->clksel_reg);    /* OCP barrier */
+	_write_clksel_reg(clk, field_val);
 
 	clk_reparent(clk, new_parent);
 
@@ -423,7 +502,7 @@ int omap2_clksel_set_parent(struct clk *clk, struct clk *new_parent)
 	if (parent_div > 0)
 		clk->rate /= parent_div;
 
-	pr_debug("clock: set parent of %s to %s (new rate %ld)\n",
+	pr_debug("clock: %s: set parent to %s (new rate %ld)\n",
 		 clk->name, clk->parent->name, clk->rate);
 
 	return 0;