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Message-Id: <1465596231-21766-44-git-send-email-alexandre.belloni@free-electrons.com>
Date: Sat, 11 Jun 2016 00:03:46 +0200
From: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
To: Nicolas Ferre <nicolas.ferre@...el.com>
Cc: Boris Brezillon <boris.brezillon@...e-electrons.com>,
Jean-Christophe Plagniol-Villard <plagnioj@...osoft.com>,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
Daniel Lezcano <daniel.lezcano@...aro.org>,
Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH 43/48] clocksource/drivers: Add a clockevent driver for Atmel TC blocks
Add an independent clockevent driver for the Atmel Timer Counter Blocks.
This driver provides a single clockevent device. using its own TCB channel.
Cc: Daniel Lezcano <daniel.lezcano@...aro.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Alexandre Belloni <alexandre.belloni@...e-electrons.com>
---
drivers/clocksource/Kconfig | 10 ++
drivers/clocksource/Makefile | 1 +
drivers/clocksource/timer-atmel-tcbclkevt.c | 220 ++++++++++++++++++++++++++++
3 files changed, 231 insertions(+)
create mode 100644 drivers/clocksource/timer-atmel-tcbclkevt.c
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index ff7f4022c749..1860f6f9b380 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -271,6 +271,16 @@ config ATMEL_ARM_TCB_CLKSRC
to make a single 32-bit timer.
It can also be used as a clock event device supporting oneshot mode.
+config ATMEL_ARM_TCB_CLKEVT
+ bool "TC Block Clockevent"
+ select REGMAP_MMIO
+ depends on GENERIC_CLOCKEVENTS
+ depends on SOC_AT91RM9200 || SOC_AT91SAM9 || SOC_SAMA5
+ default SOC_AT91RM9200 || SOC_AT91SAM9 || SOC_SAMA5
+ help
+ Select this to get a high precision clockevent device based on a TC
+ Block with the slow clock as its input.
+
config CLKSRC_METAG_GENERIC
def_bool y if METAG
help
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index 988f33de5808..c4a4155ccedc 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -3,6 +3,7 @@ obj-$(CONFIG_ATMEL_PIT) += timer-atmel-pit.o
obj-$(CONFIG_ATMEL_ST) += timer-atmel-st.o
obj-$(CONFIG_ATMEL_TCB_CLKSRC) += tcb_clksrc.o
obj-$(CONFIG_ATMEL_ARM_TCB_CLKSRC) += timer-atmel-tcbclksrc.o
+obj-$(CONFIG_ATMEL_ARM_TCB_CLKEVT) += timer-atmel-tcbclkevt.o
obj-$(CONFIG_X86_PM_TIMER) += acpi_pm.o
obj-$(CONFIG_SCx200HR_TIMER) += scx200_hrt.o
obj-$(CONFIG_CS5535_CLOCK_EVENT_SRC) += cs5535-clockevt.o
diff --git a/drivers/clocksource/timer-atmel-tcbclkevt.c b/drivers/clocksource/timer-atmel-tcbclkevt.c
new file mode 100644
index 000000000000..71440fd27b49
--- /dev/null
+++ b/drivers/clocksource/timer-atmel-tcbclkevt.c
@@ -0,0 +1,220 @@
+#include <linux/clk.h>
+#include <linux/clockchips.h>
+#include <linux/interrupt.h>
+#include <linux/kernel.h>
+#include <linux/mfd/syscon.h>
+#include <linux/module.h>
+#include <linux/of_irq.h>
+#include <linux/platform_device.h>
+#include <linux/regmap.h>
+#include <soc/at91/atmel_tcb.h>
+
+struct tc_clkevt_device {
+ struct clock_event_device clkevt;
+ struct regmap *regmap;
+ struct clk *slow_clk;
+ struct clk *clk;
+ int channel;
+ int irq;
+};
+
+static struct tc_clkevt_device *to_tc_clkevt(struct clock_event_device *clkevt)
+{
+ return container_of(clkevt, struct tc_clkevt_device, clkevt);
+}
+
+static int tc_shutdown(struct clock_event_device *d)
+{
+ struct tc_clkevt_device *tcd = to_tc_clkevt(d);
+
+ regmap_write(tcd->regmap, ATMEL_TC_IDR(tcd->channel), 0xff);
+ regmap_write(tcd->regmap, ATMEL_TC_CCR(tcd->channel),
+ ATMEL_TC_CCR_CLKDIS);
+ if (!clockevent_state_detached(d))
+ clk_disable(tcd->clk);
+
+ return 0;
+}
+
+/* For now, we always use the 32K clock ... this optimizes for NO_HZ,
+ * because using one of the divided clocks would usually mean the
+ * tick rate can never be less than several dozen Hz (vs 0.5 Hz).
+ *
+ * A divided clock could be good for high resolution timers, since
+ * 30.5 usec resolution can seem "low".
+ */
+static int tc_set_oneshot(struct clock_event_device *d)
+{
+ struct tc_clkevt_device *tcd = to_tc_clkevt(d);
+
+ if (clockevent_state_oneshot(d) || clockevent_state_periodic(d))
+ tc_shutdown(d);
+
+ clk_enable(tcd->clk);
+
+ /* slow clock, count up to RC, then irq and stop */
+ regmap_write(tcd->regmap, ATMEL_TC_CMR(tcd->channel),
+ ATMEL_TC_CMR_TCLK(4) | ATMEL_TC_CMR_CPCSTOP |
+ ATMEL_TC_CMR_WAVE | ATMEL_TC_CMR_WAVESEL_UPRC);
+ regmap_write(tcd->regmap, ATMEL_TC_IER(tcd->channel),
+ ATMEL_TC_CPCS);
+
+ return 0;
+}
+
+static int tc_set_periodic(struct clock_event_device *d)
+{
+ struct tc_clkevt_device *tcd = to_tc_clkevt(d);
+
+ if (clockevent_state_oneshot(d) || clockevent_state_periodic(d))
+ tc_shutdown(d);
+
+ /* By not making the gentime core emulate periodic mode on top
+ * of oneshot, we get lower overhead and improved accuracy.
+ */
+ clk_enable(tcd->clk);
+
+ /* slow clock, count up to RC, then irq and restart */
+ regmap_write(tcd->regmap, ATMEL_TC_CMR(tcd->channel),
+ ATMEL_TC_CMR_TCLK(4) | ATMEL_TC_CMR_WAVE |
+ ATMEL_TC_CMR_WAVESEL_UPRC);
+ regmap_write(tcd->regmap, ATMEL_TC_RC(tcd->channel),
+ (32768 + HZ / 2) / HZ);
+
+ /* Enable clock and interrupts on RC compare */
+ regmap_write(tcd->regmap, ATMEL_TC_IER(tcd->channel), ATMEL_TC_CPCS);
+ regmap_write(tcd->regmap, ATMEL_TC_CCR(tcd->channel),
+ ATMEL_TC_CCR_CLKEN | ATMEL_TC_CCR_SWTRG);
+
+ return 0;
+}
+
+static int tc_next_event(unsigned long delta, struct clock_event_device *d)
+{
+ struct tc_clkevt_device *tcd = to_tc_clkevt(d);
+
+ regmap_write(tcd->regmap, ATMEL_TC_RC(tcd->channel), delta);
+ regmap_write(tcd->regmap, ATMEL_TC_CCR(tcd->channel),
+ ATMEL_TC_CCR_CLKEN | ATMEL_TC_CCR_SWTRG);
+
+ return 0;
+}
+
+static struct tc_clkevt_device clkevt = {
+ .clkevt = {
+ .features = CLOCK_EVT_FEAT_PERIODIC |
+ CLOCK_EVT_FEAT_ONESHOT,
+ /* Should be lower than at91rm9200's system timer */
+ .rating = 140,
+ .set_next_event = tc_next_event,
+ .set_state_shutdown = tc_shutdown,
+ .set_state_periodic = tc_set_periodic,
+ .set_state_oneshot = tc_set_oneshot,
+ },
+};
+
+static irqreturn_t tc_clkevt_irq(int irq, void *handle)
+{
+ struct tc_clkevt_device *tcd = handle;
+ unsigned int sr;
+
+ regmap_read(tcd->regmap, ATMEL_TC_SR(tcd->channel), &sr);
+ if (sr & ATMEL_TC_CPCS) {
+ tcd->clkevt.event_handler(&tcd->clkevt);
+ return IRQ_HANDLED;
+ }
+
+ return IRQ_NONE;
+}
+
+static int tcb_clkevt_probe(struct platform_device *pdev)
+{
+ struct tc_clkevt_device *tcd = &clkevt;
+ int ret;
+ struct device_node *node = pdev->dev.of_node;
+
+ ret = of_property_read_u32_index(node, "reg", 0, &tcd->channel);
+ if (ret)
+ return ret;
+
+ tcd->irq = tcb_irq_get(node, tcd->channel);
+ if (tcd->irq < 0)
+ return tcd->irq;
+
+ tcd->regmap = syscon_node_to_regmap(node->parent);
+ if (IS_ERR(tcd->regmap))
+ return PTR_ERR(tcd->regmap);
+
+ tcd->slow_clk = of_clk_get_by_name(node->parent, "slow_clk");
+ if (IS_ERR(tcd->slow_clk))
+ return PTR_ERR(tcd->slow_clk);
+
+ ret = clk_prepare_enable(tcd->slow_clk);
+ if (ret)
+ return ret;
+
+ tcd->clk = tcb_clk_get(node, tcd->channel);
+ if (IS_ERR(tcd->clk)) {
+ ret = PTR_ERR(tcd->clk);
+ goto err_slow;
+ }
+
+ clkevt.clkevt.name = dev_name(&pdev->dev);
+
+ /* try to enable clk to avoid future errors in mode change */
+ ret = clk_prepare_enable(tcd->clk);
+ if (ret)
+ goto err_slow;
+
+ clk_disable(tcd->clk);
+
+ clkevt.clkevt.cpumask = cpumask_of(0);
+
+ clockevents_config_and_register(&clkevt.clkevt, 32768, 1, 0xffff);
+
+ ret = request_irq(tcd->irq, tc_clkevt_irq, IRQF_TIMER | IRQF_SHARED,
+ clkevt.clkevt.name, &clkevt);
+ if (ret)
+ goto err_clk;
+
+ return 0;
+
+err_clk:
+ clk_unprepare(tcd->clk);
+err_slow:
+ clk_disable_unprepare(tcd->slow_clk);
+
+ return ret;
+}
+
+static const struct of_device_id atmel_tcb_clkevt_dt_ids[] = {
+ { .compatible = "atmel,tcb-clkevt" },
+ { /* sentinel */ }
+};
+MODULE_DEVICE_TABLE(of, atmel_tcb_clkevt_dt_ids);
+
+static struct platform_driver tcb_clkevt_driver = {
+ .probe = tcb_clkevt_probe,
+ .driver = {
+ .name = "atmel_tcb_clkevt",
+ .of_match_table = of_match_ptr(atmel_tcb_clkevt_dt_ids),
+ },
+};
+
+static int __init atmel_tcb_clkevt_init(void)
+{
+ return platform_driver_register(&tcb_clkevt_driver);
+}
+
+static void __exit atmel_tcb_clkevt_exit(void)
+{
+ platform_driver_unregister(&tcb_clkevt_driver);
+}
+
+early_platform_init("earlytimer", &tcb_clkevt_driver);
+subsys_initcall(atmel_tcb_clkevt_init);
+module_exit(atmel_tcb_clkevt_exit);
+
+MODULE_AUTHOR("Alexandre Belloni <alexandre.belloni@...e-electrons.com>");
+MODULE_DESCRIPTION("Clockevents driver for Atmel Timer Counter Blocks");
+MODULE_LICENSE("GPL v2");
--
2.8.1
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