clocksource: add common mmio clocksource

Add a generic mmio clocksource, covering both 32-bit and 16-bit register
access sizes, for up or down counters.  This can be used to easily
create clocksources for simple counter-based implementations.

Cc: Alessandro Rubini <rubini@unipv.it>
Cc: Colin Cross <ccross@android.com>
Cc: Eric Miao <eric.y.miao@gmail.com>
Cc: Erik Gilling <konkers@android.com>
Acked-by: "Hans J. Koch" <hjk@hansjkoch.de>
Cc: Imre Kaloz <kaloz@openwrt.org>
Cc: Krzysztof Halasa <khc@pm.waw.pl>
Cc: Kukjin Kim <kgene.kim@samsung.com>
Cc: Lennert Buytenhek <kernel@wantstofly.org>
Cc: Linus Walleij <linus.walleij@stericsson.com>
Cc: linux-omap@vger.kernel.org
Acked-by: Nicolas Pitre <nico@fluxnic.net>
Cc: Olof Johansson <olof@lixom.net>
Tested-by: Sascha Hauer <s.hauer@pengutronix.de>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Tony Lindgren <tony@atomide.com>
Reviewed-by: Viresh Kumar <viresh.kumar@st.com>
Cc: Wan ZongShun <mcuos.com@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

3 files changed, 77 insertions, 0 deletions

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 110aeeb52f9a..96c921910469 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -1,2 +1,5 @@
 config CLKSRC_I8253
         bool
+
+config CLKSRC_MMIO
+        bool
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index cfb6383b543a..b995942a5060 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -7,3 +7,4 @@ obj-$(CONFIG_SH_TIMER_CMT)	+= sh_cmt.o
 obj-$(CONFIG_SH_TIMER_MTU2)     += sh_mtu2.o
 obj-$(CONFIG_SH_TIMER_TMU)      += sh_tmu.o
 obj-$(CONFIG_CLKSRC_I8253)      += i8253.o
+obj-$(CONFIG_CLKSRC_MMIO)       += mmio.o
diff --git a/drivers/clocksource/mmio.c b/drivers/clocksource/mmio.c
new file mode 100644
index 000000000000..c0e25125a55e
--- /dev/null
+++ b/drivers/clocksource/mmio.c
@@ -0,0 +1,73 @@
+/*
+ * Generic MMIO clocksource support
+ *
+ * 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.
+ */
+#include <linux/clocksource.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+
+struct clocksource_mmio {
+        void __iomem *reg;
+        struct clocksource clksrc;
+};
+
+static inline struct clocksource_mmio *to_mmio_clksrc(struct clocksource *c)
+{
+        return container_of(c, struct clocksource_mmio, clksrc);
+}
+
+cycle_t clocksource_mmio_readl_up(struct clocksource *c)
+{
+        return readl_relaxed(to_mmio_clksrc(c)->reg);
+}
+
+cycle_t clocksource_mmio_readl_down(struct clocksource *c)
+{
+        return ~readl_relaxed(to_mmio_clksrc(c)->reg);
+}
+
+cycle_t clocksource_mmio_readw_up(struct clocksource *c)
+{
+        return readw_relaxed(to_mmio_clksrc(c)->reg);
+}
+
+cycle_t clocksource_mmio_readw_down(struct clocksource *c)
+{
+        return ~(unsigned)readw_relaxed(to_mmio_clksrc(c)->reg);
+}
+
+/**
+ * clocksource_mmio_init - Initialize a simple mmio based clocksource
+ * @base:       Virtual address of the clock readout register
+ * @name:       Name of the clocksource
+ * @hz:         Frequency of the clocksource in Hz
+ * @rating:     Rating of the clocksource
+ * @bits:       Number of valid bits
+ * @read:       One of clocksource_mmio_read*() above
+ */
+int __init clocksource_mmio_init(void __iomem *base, const char *name,
+        unsigned long hz, int rating, unsigned bits,
+        cycle_t (*read)(struct clocksource *))
+{
+        struct clocksource_mmio *cs;
+
+        if (bits > 32 || bits < 16)
+                return -EINVAL;
+
+        cs = kzalloc(sizeof(struct clocksource_mmio), GFP_KERNEL);
+        if (!cs)
+                return -ENOMEM;
+
+        cs->reg = base;
+        cs->clksrc.name = name;
+        cs->clksrc.rating = rating;
+        cs->clksrc.read = read;
+        cs->clksrc.mask = CLOCKSOURCE_MASK(bits);
+        cs->clksrc.flags = CLOCK_SOURCE_IS_CONTINUOUS;
+
+        return clocksource_register_hz(&cs->clksrc, hz);
+}