clk: at91: add PMC main clock

This patch adds new at91 main oscillator clock implementation using common
clk framework.

If rate is not provided during clock registration it is calculated using
the slow clock (main clk parent in this case) rate and MCFR register.

Signed-off-by: Boris BREZILLON <b.brezillon@overkiz.com>
Acked-by: Mike Turquette <mturquette@linaro.org>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>

1 files changed, 187 insertions, 0 deletions

diff --git a/drivers/clk/at91/clk-main.c b/drivers/clk/at91/clk-main.c
new file mode 100644
index 000000000000..8e9e8cc0412d
--- /dev/null
+++ b/drivers/clk/at91/clk-main.c
@@ -0,0 +1,187 @@
+/*
+ *  Copyright (C) 2013 Boris BREZILLON <b.brezillon@overkiz.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ */
+
+#include <linux/clk-provider.h>
+#include <linux/clkdev.h>
+#include <linux/clk/at91_pmc.h>
+#include <linux/delay.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/io.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/sched.h>
+#include <linux/wait.h>
+
+#include "pmc.h"
+
+#define SLOW_CLOCK_FREQ		32768
+#define MAINF_DIV		16
+#define MAINFRDY_TIMEOUT	(((MAINF_DIV + 1) * USEC_PER_SEC) / \
+				 SLOW_CLOCK_FREQ)
+#define MAINF_LOOP_MIN_WAIT	(USEC_PER_SEC / SLOW_CLOCK_FREQ)
+#define MAINF_LOOP_MAX_WAIT	MAINFRDY_TIMEOUT
+
+struct clk_main {
+	struct clk_hw hw;
+	struct at91_pmc *pmc;
+	unsigned long rate;
+	unsigned int irq;
+	wait_queue_head_t wait;
+};
+
+#define to_clk_main(hw) container_of(hw, struct clk_main, hw)
+
+static irqreturn_t clk_main_irq_handler(int irq, void *dev_id)
+{
+	struct clk_main *clkmain = (struct clk_main *)dev_id;
+
+	wake_up(&clkmain->wait);
+	disable_irq_nosync(clkmain->irq);
+
+	return IRQ_HANDLED;
+}
+
+static int clk_main_prepare(struct clk_hw *hw)
+{
+	struct clk_main *clkmain = to_clk_main(hw);
+	struct at91_pmc *pmc = clkmain->pmc;
+	unsigned long halt_time, timeout;
+	u32 tmp;
+
+	while (!(pmc_read(pmc, AT91_PMC_SR) & AT91_PMC_MOSCS)) {
+		enable_irq(clkmain->irq);
+		wait_event(clkmain->wait,
+			   pmc_read(pmc, AT91_PMC_SR) & AT91_PMC_MOSCS);
+	}
+
+	if (clkmain->rate)
+		return 0;
+
+	timeout = jiffies + usecs_to_jiffies(MAINFRDY_TIMEOUT);
+	do {
+		halt_time = jiffies;
+		tmp = pmc_read(pmc, AT91_CKGR_MCFR);
+		if (tmp & AT91_PMC_MAINRDY)
+			return 0;
+		usleep_range(MAINF_LOOP_MIN_WAIT, MAINF_LOOP_MAX_WAIT);
+	} while (time_before(halt_time, timeout));
+
+	return 0;
+}
+
+static int clk_main_is_prepared(struct clk_hw *hw)
+{
+	struct clk_main *clkmain = to_clk_main(hw);
+
+	return !!(pmc_read(clkmain->pmc, AT91_PMC_SR) & AT91_PMC_MOSCS);
+}
+
+static unsigned long clk_main_recalc_rate(struct clk_hw *hw,
+					  unsigned long parent_rate)
+{
+	u32 tmp;
+	struct clk_main *clkmain = to_clk_main(hw);
+	struct at91_pmc *pmc = clkmain->pmc;
+
+	if (clkmain->rate)
+		return clkmain->rate;
+
+	tmp = pmc_read(pmc, AT91_CKGR_MCFR) & AT91_PMC_MAINF;
+	clkmain->rate = (tmp * parent_rate) / MAINF_DIV;
+
+	return clkmain->rate;
+}
+
+static const struct clk_ops main_ops = {
+	.prepare = clk_main_prepare,
+	.is_prepared = clk_main_is_prepared,
+	.recalc_rate = clk_main_recalc_rate,
+};
+
+static struct clk * __init
+at91_clk_register_main(struct at91_pmc *pmc,
+		       unsigned int irq,
+		       const char *name,
+		       const char *parent_name,
+		       unsigned long rate)
+{
+	int ret;
+	struct clk_main *clkmain;
+	struct clk *clk = NULL;
+	struct clk_init_data init;
+
+	if (!pmc || !irq || !name)
+		return ERR_PTR(-EINVAL);
+
+	if (!rate && !parent_name)
+		return ERR_PTR(-EINVAL);
+
+	clkmain = kzalloc(sizeof(*clkmain), GFP_KERNEL);
+	if (!clkmain)
+		return ERR_PTR(-ENOMEM);
+
+	init.name = name;
+	init.ops = &main_ops;
+	init.parent_names = parent_name ? &parent_name : NULL;
+	init.num_parents = parent_name ? 1 : 0;
+	init.flags = parent_name ? 0 : CLK_IS_ROOT;
+
+	clkmain->hw.init = &init;
+	clkmain->rate = rate;
+	clkmain->pmc = pmc;
+	clkmain->irq = irq;
+	init_waitqueue_head(&clkmain->wait);
+	irq_set_status_flags(clkmain->irq, IRQ_NOAUTOEN);
+	ret = request_irq(clkmain->irq, clk_main_irq_handler,
+			  IRQF_TRIGGER_HIGH, "clk-main", clkmain);
+	if (ret)
+		return ERR_PTR(ret);
+
+	clk = clk_register(NULL, &clkmain->hw);
+	if (IS_ERR(clk)) {
+		free_irq(clkmain->irq, clkmain);
+		kfree(clkmain);
+	}
+
+	return clk;
+}
+
+
+
+static void __init
+of_at91_clk_main_setup(struct device_node *np, struct at91_pmc *pmc)
+{
+	struct clk *clk;
+	unsigned int irq;
+	const char *parent_name;
+	const char *name = np->name;
+	u32 rate = 0;
+
+	parent_name = of_clk_get_parent_name(np, 0);
+	of_property_read_string(np, "clock-output-names", &name);
+	of_property_read_u32(np, "clock-frequency", &rate);
+	irq = irq_of_parse_and_map(np, 0);
+	if (!irq)
+		return;
+
+	clk = at91_clk_register_main(pmc, irq, name, parent_name, rate);
+	if (IS_ERR(clk))
+		return;
+
+	of_clk_add_provider(np, of_clk_src_simple_get, clk);
+}
+
+void __init of_at91rm9200_clk_main_setup(struct device_node *np,
+					 struct at91_pmc *pmc)
+{
+	of_at91_clk_main_setup(np, pmc);
+}