[PATCH] clk: vexpress: Add separate SP810 driver

[mturquette@linaro.org (Mike Turquette)]

Quoting Pawel Moll (2013-03-15 07:40:09)
> +static int clk_sp810_timerclken_prepare(struct clk_hw *hw)
> +{
> +       struct clk_sp810_timerclken *timerclken = to_clk_sp810_timerclken(hw);
> +       struct clk_sp810 *sp810 = timerclken->sp810;
> +       struct clk *refclk = of_clk_get(sp810->node, sp810->refclk_index);
> +       struct clk *timclk = of_clk_get(sp810->node, sp810->timclk_index);
> +       struct clk *old_parent = __clk_get_parent(hw->clk);
> +       struct clk *new_parent = old_parent;
> +       int new_parent_index;
> +
> +       if (WARN_ON(IS_ERR(refclk) || IS_ERR(timclk)))
> +               return -ENOENT;
> +
> +       /* Select "better" (faster) parent */
> +       if (__clk_get_rate(refclk) > __clk_get_rate(timclk)) {
> +               new_parent = refclk;
> +               new_parent_index = 0;
> +       } else {
> +               new_parent = timclk;
> +               new_parent_index = 1;
> +       }
> +
> +       /* Switch the parent if necessary */
> +       if (old_parent != new_parent) {
> +               __clk_prepare(new_parent);
> +               clk_sp810_timerclken_set_parent(hw, new_parent_index);
> +               __clk_reparent(hw->clk, new_parent);
> +               __clk_unprepare(old_parent);
> +       }

The reentrancy patch makes some of this less messy.  I have a re-worked
patch below demonstrating this.

> +
> +       return 0;
> +}
> +
> +static const struct clk_ops clk_sp810_timerclken_ops = {
> +       .prepare = clk_sp810_timerclken_prepare,
> +       .get_parent = clk_sp810_timerclken_get_parent,
> +       .set_parent = clk_sp810_timerclken_set_parent,
> +};

I dislike these one-off clk_prepare hacks.  Any time I see a .prepare
callback and not a matching .unprepare callback I know something is
wrong.  At a minimum you should be calling clk_put for the clocks you
"get" from of_clk_get.

In this case you are using clk_prepare for one-time configuration.  I
agree that no alternative exists yet, but there have been discussions
recently about using DT for configuration details that are not strictly
descriptions of the hardware.  I've added a comment block in the patch
below which notes this with a FIXME since there isn't a graceful
alternative to using clk_prepare for ont-time configuration.

Can you test the patch below against the latest clk-next and let me know
if it working on your platform?

Regards,
Mike



>From e3f11f34d4f7d3c6c89c43c2100f246d3b91e903 Mon Sep 17 00:00:00 2001
From: Pawel Moll <pawel.moll@arm.com>
Date: Fri, 15 Mar 2013 14:40:09 +0000
Subject: [PATCH] clk: vexpress: Add separate SP810 driver

Factor out the SP810 clocking code into a separate driver,
selecting better (faster) parent at clk_prepare() time.
This is to avoid problems with clocking infrastructure
initialisation order, in particular to avoid dependency
of fixed clock being initialized before SP810. It also
makes vexpress platform OF-based clock initialisation code
unnecessary.

Signed-off-by: Pawel Moll <pawel.moll@arm.com>
Tested-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>
[mturquette at linaro.org: add .unprepare, FIXME comment, cleaned up code]
---
 arch/arm/mach-vexpress/v2m.c         |    8 +-
 drivers/clk/versatile/Makefile       |    2 +-
 drivers/clk/versatile/clk-sp810.c    |  186 ++++++++++++++++++++++++++++++++++
 drivers/clk/versatile/clk-vexpress.c |   49 ---------
 4 files changed, 194 insertions(+), 51 deletions(-)
 create mode 100644 drivers/clk/versatile/clk-sp810.c

diff --git a/arch/arm/mach-vexpress/v2m.c b/arch/arm/mach-vexpress/v2m.c
index 915683c..c5e20b5 100644
--- a/arch/arm/mach-vexpress/v2m.c
+++ b/arch/arm/mach-vexpress/v2m.c
@@ -21,6 +21,8 @@
 #include <linux/regulator/fixed.h>
 #include <linux/regulator/machine.h>
 #include <linux/vexpress.h>
+#include <linux/clk-provider.h>
+#include <linux/clkdev.h>
 
 #include <asm/arch_timer.h>
 #include <asm/mach-types.h>
@@ -433,7 +435,7 @@ static void __init v2m_dt_timer_init(void)
 {
 	struct device_node *node = NULL;
 
-	vexpress_clk_of_init();
+	of_clk_init(NULL);
 
 	do {
 		node = of_find_compatible_node(node, NULL, "arm,sp804");
@@ -441,6 +443,10 @@ static void __init v2m_dt_timer_init(void)
 	if (node) {
 		pr_info("Using SP804 '%s' as a clock & events source\n",
 				node->full_name);
+		WARN_ON(clk_register_clkdev(of_clk_get_by_name(node,
+				"timclken1"), "v2m-timer0", "sp804"));
+		WARN_ON(clk_register_clkdev(of_clk_get_by_name(node,
+				"timclken2"), "v2m-timer1", "sp804"));
 		v2m_sp804_init(of_iomap(node, 0),
 				irq_of_parse_and_map(node, 0));
 	}
diff --git a/drivers/clk/versatile/Makefile b/drivers/clk/versatile/Makefile
index ec3b88f..c16ca78 100644
--- a/drivers/clk/versatile/Makefile
+++ b/drivers/clk/versatile/Makefile
@@ -3,5 +3,5 @@ obj-$(CONFIG_ICST)		+= clk-icst.o
 obj-$(CONFIG_ARCH_INTEGRATOR)	+= clk-integrator.o
 obj-$(CONFIG_INTEGRATOR_IMPD1)	+= clk-impd1.o
 obj-$(CONFIG_ARCH_REALVIEW)	+= clk-realview.o
-obj-$(CONFIG_ARCH_VEXPRESS)	+= clk-vexpress.o
+obj-$(CONFIG_ARCH_VEXPRESS)	+= clk-vexpress.o clk-sp810.o
 obj-$(CONFIG_VEXPRESS_CONFIG)	+= clk-vexpress-osc.o
diff --git a/drivers/clk/versatile/clk-sp810.c b/drivers/clk/versatile/clk-sp810.c
new file mode 100644
index 0000000..295375a
--- /dev/null
+++ b/drivers/clk/versatile/clk-sp810.c
@@ -0,0 +1,186 @@
+/*
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * Copyright (C) 2013 ARM Limited
+ */
+
+#include <linux/amba/sp810.h>
+#include <linux/clkdev.h>
+#include <linux/clk-provider.h>
+#include <linux/err.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+
+#define to_clk_sp810_timerclken(_hw) \
+		container_of(_hw, struct clk_sp810_timerclken, hw)
+
+struct clk_sp810;
+
+struct clk_sp810_timerclken {
+	struct clk_hw hw;
+	struct clk *clk;
+	struct clk_sp810 *sp810;
+	int channel;
+};
+
+struct clk_sp810 {
+	struct device_node *node;
+	int refclk_index, timclk_index;
+	void __iomem *base;
+	spinlock_t lock;
+	struct clk_sp810_timerclken timerclken[4];
+	struct clk *refclk;
+	struct clk *timclk;
+};
+
+static u8 clk_sp810_timerclken_get_parent(struct clk_hw *hw)
+{
+	struct clk_sp810_timerclken *timerclken = to_clk_sp810_timerclken(hw);
+	u32 val = readl(timerclken->sp810->base + SCCTRL);
+
+	return !!(val & (1 << SCCTRL_TIMERENnSEL_SHIFT(timerclken->channel)));
+}
+
+static int clk_sp810_timerclken_set_parent(struct clk_hw *hw, u8 index)
+{
+	struct clk_sp810_timerclken *timerclken = to_clk_sp810_timerclken(hw);
+	struct clk_sp810 *sp810 = timerclken->sp810;
+	u32 val, shift = SCCTRL_TIMERENnSEL_SHIFT(timerclken->channel);
+	unsigned long flags = 0;
+
+	if (WARN_ON(index > 1))
+		return -EINVAL;
+
+	spin_lock_irqsave(&sp810->lock, flags);
+
+	val = readl(sp810->base + SCCTRL);
+	val &= ~(1 << shift);
+	val |= index << shift;
+	writel(val, sp810->base + SCCTRL);
+
+	spin_unlock_irqrestore(&sp810->lock, flags);
+
+	return 0;
+}
+
+/*
+ * FIXME - setting the parent every time .prepare is invoked is inefficient.
+ * This is better handled by a dedicated clock tree configuration mechanism at
+ * init-time.  Revisit this later when such a mechanism exists
+ */
+static int clk_sp810_timerclken_prepare(struct clk_hw *hw)
+{
+	struct clk_sp810_timerclken *timerclken = to_clk_sp810_timerclken(hw);
+	struct clk_sp810 *sp810 = timerclken->sp810;
+	struct clk *old_parent = __clk_get_parent(hw->clk);
+	struct clk *new_parent;
+
+	if (!sp810->refclk)
+		sp810->refclk = of_clk_get(sp810->node, sp810->refclk_index);
+
+	if (!sp810->timclk)
+		sp810->timclk = of_clk_get(sp810->node, sp810->timclk_index);
+
+	if (WARN_ON(IS_ERR(sp810->refclk) || IS_ERR(sp810->timclk)))
+		return -ENOENT;
+
+	/* Select fastest parent */
+	if (clk_get_rate(sp810->refclk) > clk_get_rate(sp810->timclk)) {
+		new_parent = sp810->refclk;
+	} else {
+		new_parent = sp810->timclk;
+	}
+
+	/* Switch the parent if necessary */
+	if (old_parent != new_parent)
+		clk_set_parent(hw->clk, new_parent);
+
+	return 0;
+}
+
+static void clk_sp810_timerclken_unprepare(struct clk_hw *hw)
+{
+	struct clk_sp810_timerclken *timerclken = to_clk_sp810_timerclken(hw);
+	struct clk_sp810 *sp810 = timerclken->sp810;
+
+	clk_put(sp810->timclk);
+	clk_put(sp810->refclk);
+}
+
+static const struct clk_ops clk_sp810_timerclken_ops = {
+	.prepare = clk_sp810_timerclken_prepare,
+	.unprepare = clk_sp810_timerclken_unprepare,
+	.get_parent = clk_sp810_timerclken_get_parent,
+	.set_parent = clk_sp810_timerclken_set_parent,
+};
+
+struct clk *clk_sp810_timerclken_of_get(struct of_phandle_args *clkspec,
+		void *data)
+{
+	struct clk_sp810 *sp810 = data;
+
+	if (WARN_ON(clkspec->args_count != 1 || clkspec->args[0] >
+			ARRAY_SIZE(sp810->timerclken)))
+		return NULL;
+
+	return sp810->timerclken[clkspec->args[0]].clk;
+}
+
+void __init clk_sp810_of_setup(struct device_node *node)
+{
+	struct clk_sp810 *sp810 = kzalloc(sizeof(*sp810), GFP_KERNEL);
+	const char *parent_names[2];
+	char name[12];
+	struct clk_init_data init;
+	int i;
+
+	if (!sp810) {
+		pr_err("Failed to allocate memory for SP810!\n");
+		return;
+	}
+
+	sp810->refclk_index = of_property_match_string(node, "clock-names",
+			"refclk");
+	parent_names[0] = of_clk_get_parent_name(node, sp810->refclk_index);
+
+	sp810->timclk_index = of_property_match_string(node, "clock-names",
+			"timclk");
+	parent_names[1] = of_clk_get_parent_name(node, sp810->timclk_index);
+
+	if (parent_names[0] <= 0 || parent_names[1] <= 0) {
+		pr_warn("Failed to obtain parent clocks for SP810!\n");
+		return;
+	}
+
+	sp810->node = node;
+	sp810->base = of_iomap(node, 0);
+	spin_lock_init(&sp810->lock);
+
+	init.name = name;
+	init.ops = &clk_sp810_timerclken_ops;
+	init.flags = CLK_IS_BASIC;
+	init.parent_names = parent_names;
+	init.num_parents = ARRAY_SIZE(parent_names);
+
+	for (i = 0; i < ARRAY_SIZE(sp810->timerclken); i++) {
+		snprintf(name, ARRAY_SIZE(name), "timerclken%d", i);
+
+		sp810->timerclken[i].sp810 = sp810;
+		sp810->timerclken[i].channel = i;
+		sp810->timerclken[i].hw.init = &init;
+
+		sp810->timerclken[i].clk = clk_register(NULL,
+				&sp810->timerclken[i].hw);
+		WARN_ON(IS_ERR(sp810->timerclken[i].clk));
+	}
+
+	of_clk_add_provider(node, clk_sp810_timerclken_of_get, sp810);
+}
+CLK_OF_DECLARE(sp810, "arm,sp810", clk_sp810_of_setup);
diff --git a/drivers/clk/versatile/clk-vexpress.c b/drivers/clk/versatile/clk-vexpress.c
index 82b45aa..a4a728d 100644
--- a/drivers/clk/versatile/clk-vexpress.c
+++ b/drivers/clk/versatile/clk-vexpress.c
@@ -15,8 +15,6 @@
 #include <linux/clkdev.h>
 #include <linux/clk-provider.h>
 #include <linux/err.h>
-#include <linux/of.h>
-#include <linux/of_address.h>
 #include <linux/vexpress.h>
 
 static struct clk *vexpress_sp810_timerclken[4];
@@ -86,50 +84,3 @@ void __init vexpress_clk_init(void __iomem *sp810_base)
 	WARN_ON(clk_register_clkdev(vexpress_sp810_timerclken[1],
 				"v2m-timer1", "sp804"));
 }
-
-#if defined(CONFIG_OF)
-
-struct clk *vexpress_sp810_of_get(struct of_phandle_args *clkspec, void *data)
-{
-	if (WARN_ON(clkspec->args_count != 1 || clkspec->args[0] >
-			ARRAY_SIZE(vexpress_sp810_timerclken)))
-		return NULL;
-
-	return vexpress_sp810_timerclken[clkspec->args[0]];
-}
-
-void __init vexpress_clk_of_init(void)
-{
-	struct device_node *node;
-	struct clk *clk;
-	struct clk *refclk, *timclk;
-
-	of_clk_init(NULL);
-
-	node = of_find_compatible_node(NULL, NULL, "arm,sp810");
-	vexpress_sp810_init(of_iomap(node, 0));
-	of_clk_add_provider(node, vexpress_sp810_of_get, NULL);
-
-	/* Select "better" (faster) parent for SP804 timers */
-	refclk = of_clk_get_by_name(node, "refclk");
-	timclk = of_clk_get_by_name(node, "timclk");
-	if (!WARN_ON(IS_ERR(refclk) || IS_ERR(timclk))) {
-		int i = 0;
-
-		if (clk_get_rate(refclk) > clk_get_rate(timclk))
-			clk = refclk;
-		else
-			clk = timclk;
-
-		for (i = 0; i < ARRAY_SIZE(vexpress_sp810_timerclken); i++)
-			WARN_ON(clk_set_parent(vexpress_sp810_timerclken[i],
-					clk));
-	}
-
-	WARN_ON(clk_register_clkdev(vexpress_sp810_timerclken[0],
-				"v2m-timer0", "sp804"));
-	WARN_ON(clk_register_clkdev(vexpress_sp810_timerclken[1],
-				"v2m-timer1", "sp804"));
-}
-
-#endif
-- 
1.7.10.4