clockevents: Add a clkevt-of mechanism like clksrc-of

The current code uses the CLOCKSOURCE_OF_DECLARE macro to fill the clksrc
table with a t-uple (name, init_function).

Unfortunately it ends up to the clockevent and the clocksource being
both initialized with this macro. It is not a problem by itself but there
is not a clear distinction between a clockevent and a clocksource in the
code initialization path. Somebody can argue there are the same IP block
and the same DT node. But conceptually from the software side, there are
two distincts entities and as is they should be initialized separetely.
Some drivers which do not have a clocksource end up by using the
CLOCKSOURCE_OF_DECLARE macro to declare a clockevent.

Another result is the fuzzy organization in the clocksource directory,
where the clockevents are implemented in the same file than the
clocksources or file labelled timer-something implementing a clocksource.

This patch provides another macro to specifically declare a clockevent in
the same way than the clocksource and gives the opportunity to write two
separate drivers, one for the clocksource and another for the clockevents.

Hopefully, that can help to do some housework in the directory, perhaps
split the drivers in to entities, for example:
	- clksrc-rockchip.c
	- clkevt-rockchip.c

Also, it gives the possibility to declare clocksources separately in the
DT and then use a clocksource from IP block while while clockevents are
used from another IP block.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

drivers/clocksource/Kconfig

@@ -5,13 +5,20 @@ config CLKSRC_OF
 	bool
 	select CLKSRC_PROBE
 
+config CLKEVT_OF
+	bool
+	select CLKEVT_PROBE
+
 config CLKSRC_ACPI
 	bool
 	select CLKSRC_PROBE
 
 config CLKSRC_PROBE
 	bool
 
+config CLKEVT_PROBE
+	bool
+
 config CLKSRC_I8253
 	bool
 

drivers/clocksource/Makefile

@@ -1,4 +1,5 @@
 obj-$(CONFIG_CLKSRC_PROBE)	+= clksrc-probe.o
+obj-$(CONFIG_CLKEVT_PROBE)	+= clkevt-probe.o
 obj-$(CONFIG_ATMEL_PIT)		+= timer-atmel-pit.o
 obj-$(CONFIG_ATMEL_ST)		+= timer-atmel-st.o
 obj-$(CONFIG_ATMEL_TCB_CLKSRC)	+= tcb_clksrc.o

drivers/clocksource/clkevt-probe.c

@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2016, Linaro Ltd.  All rights reserved.
+ * Daniel Lezcano <daniel.lezcano@linaro.org>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope 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.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/init.h>
+#include <linux/of.h>
+#include <linux/clockchip.h>
+
+extern struct of_device_id __clkevt_of_table[];
+
+static const struct of_device_id __clkevt_of_table_sentinel
+	__used __section(__clkevt_of_table_end);
+
+int __init clockevent_probe(void)
+{
+	struct device_node *np;
+	const struct of_device_id *match;
+	of_init_fn_1_ret init_func;
+	int ret, clockevents = 0;
+
+	for_each_matching_node_and_match(np, __clkevt_of_table, &match) {
+		if (!of_device_is_available(np))
+			continue;
+
+		init_func = match->data;
+
+		ret = init_func(np);
+		if (ret) {
+			pr_warn("Failed to initialize '%s' (%d)\n",
+				np->name, ret);
+			continue;
+		}
+
+		clockevents++;
+	}
+
+	if (!clockevents) {
+		pr_crit("%s: no matching clockevent found\n", __func__);
+		return -ENODEV;
+	}
+
+	return 0;
+}

include/linux/clockchips.h

@@ -224,4 +224,13 @@ static inline void tick_setup_hrtimer_broadcast(void) { }
 
 #endif /* !CONFIG_GENERIC_CLOCKEVENTS */
 
+#define CLOCKEVENT_OF_DECLARE(name, compat, fn) \
+	OF_DECLARE_1_RET(clkevt, name, compat, fn)
+
+#ifdef CONFIG_CLKEVT_PROBE
+extern int clockevent_probe(void);
+#els
+static inline int clockevent_probe(void) { return 0; }
+#endif
+
 #endif /* _LINUX_CLOCKCHIPS_H */