[PATCH v2.1 02/12] clocksource: sti: Provide support for the ST LPC Clocksource IP

Lee Jones
2015-05-26T12:50:11Z

clocksource: sti: Provide support for the ST LPC Clocksource IP

This IP is shared with Watchdog and RTC functionality. All 3 of
these devices are mutually exclusive from one another i.e. Only 1
IP can be used at any given time. We use the device-driver model
combined with a DT 'mode' property to enforce this.

The ST LPC Clocksource IP can be used as the system (tick) timer.

Signed-off-by: Lee Jones <lee.jones@linaro.org>

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 68161f7..01a07a6 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -250,4 +250,13 @@ config CLKSRC_PXA
help
This enables OST0 support available on PXA and SA-11x0
platforms.
+
+config CLKSRC_ST_LPC
+ bool
+ depends on ARCH_STI
+ select CLKSRC_OF if OF
+ help
+ Enable this option to use the Low Power controller timer
+ as clocksource.
+
endmenu
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index 752d5c7..e08da4d 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -51,3 +51,4 @@ obj-$(CONFIG_ARCH_INTEGRATOR_AP) += timer-integrator-ap.o
obj-$(CONFIG_CLKSRC_VERSATILE) += versatile.o
obj-$(CONFIG_CLKSRC_MIPS_GIC) += mips-gic-timer.o
obj-$(CONFIG_ASM9260_TIMER) += asm9260_timer.o
+obj-$(CONFIG_CLKSRC_ST_LPC) += clksrc_st_lpc.o
diff --git a/drivers/clocksource/clksrc_st_lpc.c b/drivers/clocksource/clksrc_st_lpc.c
new file mode 100644
index 0000000..f38cf33
--- /dev/null
+++ b/drivers/clocksource/clksrc_st_lpc.c
@@ -0,0 +1,123 @@
+/*
+ * Clocksource using the Low Power Timer found in the Low Power Controller (LPC)
+ *
+ * Copyright (C) 2015 STMicroelectronics – All Rights Reserved
+ *
+ * Author(s): Francesco Virlinzi <francesco.virlinzi@st.com>
+ * Ajit Pal Singh <ajitpal.singh@st.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.h>
+#include <linux/clocksource.h>
+#include <linux/init.h>
+#include <linux/of_address.h>
+#include <linux/slab.h>
+
+#include <dt-bindings/mfd/st-lpc.h>
+
+/* Low Power Timer */
+#define LPC_LPT_LSB_OFF 0x400
+#define LPC_LPT_MSB_OFF 0x404
+#define LPC_LPT_START_OFF 0x408
+
+static struct st_clksrc_ddata {
+ struct clk *clk;
+ void __iomem *base;
+} ddata;
+
+static void __init st_clksrc_reset(void)
+{
+ writel_relaxed(0, ddata.base + LPC_LPT_START_OFF);
+ writel_relaxed(0, ddata.base + LPC_LPT_MSB_OFF);
+ writel_relaxed(0, ddata.base + LPC_LPT_LSB_OFF);
+ writel_relaxed(1, ddata.base + LPC_LPT_START_OFF);
+}
+
+static int __init st_clksrc_init(void)
+{
+ unsigned long rate;
+ int ret;
+
+ st_clksrc_reset();
+
+ rate = clk_get_rate(ddata.clk);
+
+ ret = clocksource_mmio_init(ddata.base + LPC_LPT_LSB_OFF,
+ "clksrc-st-lpc", rate, 300, 32,
+ clocksource_mmio_readl_up);
+ if (ret) {
+ pr_err("clksrc-st-lpc: Failed to register clocksource\n");
+ return ret;
+ }
+
+ return 0;
+}
+
+static int __init st_clksrc_setup_clk(struct device_node *np)
+{
+ struct clk *clk;
+
+ clk = of_clk_get(np, 0);
+ if (IS_ERR(clk)) {
+ pr_err("clksrc-st-lpc: Failed to get LPC clock\n");
+ return PTR_ERR(clk);
+ }
+
+ if (clk_prepare_enable(clk)) {
+ pr_err("clksrc-st-lpc: Failed to enable LPC clock\n");
+ return -EINVAL;
+ }
+
+ if (!clk_get_rate(clk)) {
+ pr_err("clksrc-st-lpc: Failed to get LPC clock rate\n");
+ clk_disable_unprepare(clk);
+ return -EINVAL;
+ }
+
+ ddata.clk = clk;
+
+ return 0;
+}
+
+static void __init st_clksrc_of_register(struct device_node *np)
+{
+ int ret;
+ uint32_t mode;
+
+ ret = of_property_read_u32(np, "st,lpc-mode", &mode);
+ if (ret) {
+ pr_err("clksrc-st-lpc: An LPC mode must be provided\n");
+ return;
+ }
+
+ /* LPC can either run as a Clocksource or in RTC or WDT mode */
+ if (mode != ST_LPC_MODE_CLKSRC)
+ return;
+
+ ddata.base = of_iomap(np, 0);
+ if (!ddata.base) {
+ pr_err("clksrc-st-lpc: Unable to map iomem\n");
+ return;
+ }
+
+ if (st_clksrc_setup_clk(np)) {
+ iounmap(ddata.base);
+ return;
+ }
+
+ if (st_clksrc_init()) {
+ clk_disable_unprepare(ddata.clk);
+ clk_put(ddata.clk);
+ iounmap(ddata.base);
+ return;
+ }
+
+ pr_info("clksrc-st-lpc: clocksource initialised - running @ %luHz\n",
+ clk_get_rate(ddata.clk));
+}
+CLOCKSOURCE_OF_DECLARE(ddata, "st,stih407-lpc", st_clksrc_of_register);