Re: [PATCH v4 12/42] clocksource: ep93xx: Add driver for Cirrus Logic EP93xx
From: Daniel Lezcano
Date: Wed Oct 11 2023 - 09:30:23 EST
On 15/09/2023 10:10, Nikita Shubin via B4 Relay wrote:
From: Nikita Shubin <nikita.shubin@xxxxxxxxxxx>
Rewrite EP93xx timer driver located in arch/arm/mach-ep93xx/timer-ep93xx.c
trying to do everything the device tree way:
- Make every IO-access relative to a base address and dynamic
so we can do a dynamic ioremap and get going.
- Find register range and interrupt from the device tree.
Reviewed-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
Tested-by: Alexander Sverdlin <alexander.sverdlin@xxxxxxxxx>
Signed-off-by: Nikita Shubin <nikita.shubin@xxxxxxxxxxx>
---
drivers/clocksource/Kconfig | 11 +++
drivers/clocksource/Makefile | 1 +
drivers/clocksource/timer-ep93xx.c | 190 +++++++++++++++++++++++++++++++++++++
3 files changed, 202 insertions(+)
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index c4d671a5a13d..f1b84b05b281 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -739,4 +739,15 @@ config GOLDFISH_TIMER
help
Support for the timer/counter of goldfish-rtc
+config EP93XX_TIMER
+ bool "Cirrus Logic ep93xx timer driver" if COMPILE_TEST
+ depends on ARCH_EP93XX
Remove this dependency so it would be possible to compile-test on other
platforms.
+ depends on GENERIC_CLOCKEVENTS
This dependency is explicit for all the drivers belonging to this
Kconfig. No need to add it.
+ depends on HAS_IOMEM
+ select CLKSRC_MMIO
+ select TIMER_OF
+ help
+ Enables support for the Cirrus Logic timer block
+ EP93XX.
+
endmenu
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index 5d93c9e3fc55..b6a3cf1f5b9d 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -90,3 +90,4 @@ obj-$(CONFIG_MSC313E_TIMER) += timer-msc313e.o
obj-$(CONFIG_GOLDFISH_TIMER) += timer-goldfish.o
obj-$(CONFIG_GXP_TIMER) += timer-gxp.o
obj-$(CONFIG_CLKSRC_LOONGSON1_PWM) += timer-loongson1-pwm.o
+obj-$(CONFIG_EP93XX_TIMER) += timer-ep93xx.o
diff --git a/drivers/clocksource/timer-ep93xx.c b/drivers/clocksource/timer-ep93xx.c
new file mode 100644
index 000000000000..bc0ca6e12334
--- /dev/null
+++ b/drivers/clocksource/timer-ep93xx.c
@@ -0,0 +1,190 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Cirrus Logic EP93xx timer driver.
+ * Copyright (C) 2021 Nikita Shubin <nikita.shubin@xxxxxxxxxxx>
+ *
+ * Based on a rewrite of arch/arm/mach-ep93xx/timer.c:
+ */
+
+#include <linux/clockchips.h>
+#include <linux/clocksource.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/io.h>
+#include <linux/io-64-nonatomic-lo-hi.h>
+#include <linux/irq.h>
+#include <linux/kernel.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/sched_clock.h>
+
+#include <asm/mach/time.h>
This head should not be needed.
+
+/*************************************************************************
+ * Timer handling for EP93xx
+ *************************************************************************
+ * The ep93xx has four internal timers. Timers 1, 2 (both 16 bit) and
+ * 3 (32 bit) count down at 508 kHz, are self-reloading, and can generate
+ * an interrupt on underflow. Timer 4 (40 bit) counts down at 983.04 kHz,
+ * is free-running, and can't generate interrupts.
+ *
+ * The 508 kHz timers are ideal for use for the timer interrupt, as the
+ * most common values of HZ divide 508 kHz nicely. We pick the 32 bit
+ * timer (timer 3) to get as long sleep intervals as possible when using
+ * CONFIG_NO_HZ.
+ *
+ * The higher clock rate of timer 4 makes it a better choice than the
+ * other timers for use as clock source and for sched_clock(), providing
+ * a stable 40 bit time base.
+ *************************************************************************
+ */
+
+#define EP93XX_TIMER1_LOAD 0x00
+#define EP93XX_TIMER1_VALUE 0x04
+#define EP93XX_TIMER1_CONTROL 0x08
+#define EP93XX_TIMER123_CONTROL_ENABLE BIT(7)
+#define EP93XX_TIMER123_CONTROL_MODE BIT(6)
+#define EP93XX_TIMER123_CONTROL_CLKSEL BIT(3)
+#define EP93XX_TIMER1_CLEAR 0x0c
+#define EP93XX_TIMER2_LOAD 0x20
+#define EP93XX_TIMER2_VALUE 0x24
+#define EP93XX_TIMER2_CONTROL 0x28
+#define EP93XX_TIMER2_CLEAR 0x2c
+/*
+ * This read-only register contains the low word of the time stamp debug timer
+ * ( Timer4). When this register is read, the high byte of the Timer4 counter is
+ * saved in the Timer4ValueHigh register.
+ */
+#define EP93XX_TIMER4_VALUE_LOW 0x60
+#define EP93XX_TIMER4_VALUE_HIGH 0x64
+#define EP93XX_TIMER4_VALUE_HIGH_ENABLE BIT(8)
+#define EP93XX_TIMER3_LOAD 0x80
+#define EP93XX_TIMER3_VALUE 0x84
+#define EP93XX_TIMER3_CONTROL 0x88
+#define EP93XX_TIMER3_CLEAR 0x8c
+
+#define EP93XX_TIMER123_RATE 508469
+#define EP93XX_TIMER4_RATE 983040
+
+struct ep93xx_tcu {
+ void __iomem *base;
+};
+
+static struct ep93xx_tcu *ep93xx_tcu;
Usually what is done is:
struct ep93xx_tcu {
void __iomem *base;
struct clock_event_device evt;
};
And with container_of and all timer API passing the *evt as parameter,
we can retrieve this data.
So we should have:
struct ep93xx_tcu timer = {
.evt = {
.name = "timer1",
.features = CLOCK_EVT_FEAT_ONESHOT,
.set_state_shutdown = ep93xx_clkevt_shutdown,
.set_state_oneshot = ep93xx_clkevt_shutdown,
.tick_resume = ep93xx_clkevt_shutdown,
.set_next_event = ep93xx_clkevt_set_next_event,
.rating = 300,
};
/* No need to compute every time */
void __iomem *clksrc_base; /* base + timer4_val_low */
void __iomem *clkevt_base;
};
And no need to allocate in the init function.
+static u64 ep93xx_clocksource_read(struct clocksource *c)
Perhaps add __may_be_unused annotation
+{
+ struct ep93xx_tcu *tcu = ep93xx_tcu;
+
+ return lo_hi_readq(tcu->base + EP93XX_TIMER4_VALUE_LOW) & GENMASK_ULL(39, 0);
+}
+
+static u64 notrace ep93xx_read_sched_clock(void)
+{
+ return ep93xx_clocksource_read(NULL);
+}
+static int ep93xx_clkevt_set_next_event(unsigned long next,
+ struct clock_event_device *evt)
+{
+ struct ep93xx_tcu *tcu = ep93xx_tcu;
+ /* Default mode: periodic, off, 508 kHz */
+ u32 tmode = EP93XX_TIMER123_CONTROL_MODE |
+ EP93XX_TIMER123_CONTROL_CLKSEL;
+
+ /* Clear timer */
+ writel(tmode, tcu->base + EP93XX_TIMER3_CONTROL);
+
+ /* Set next event */
+ writel(next, tcu->base + EP93XX_TIMER3_LOAD);
+ writel(tmode | EP93XX_TIMER123_CONTROL_ENABLE,
+ tcu->base + EP93XX_TIMER3_CONTROL);
+ return 0;
+}
+
+static int ep93xx_clkevt_shutdown(struct clock_event_device *evt)
+{
+ struct ep93xx_tcu *tcu = ep93xx_tcu;
+ /* Disable timer */
+ writel(0, tcu->base + EP93XX_TIMER3_CONTROL);
+
+ return 0;
+}
+
+static struct clock_event_device ep93xx_clockevent = {
+ .name = "timer1",
+ .features = CLOCK_EVT_FEAT_ONESHOT,
+ .set_state_shutdown = ep93xx_clkevt_shutdown,
+ .set_state_oneshot = ep93xx_clkevt_shutdown,
+ .tick_resume = ep93xx_clkevt_shutdown,
+ .set_next_event = ep93xx_clkevt_set_next_event,
+ .rating = 300,
+};
+
+static irqreturn_t ep93xx_timer_interrupt(int irq, void *dev_id)
+{
+ struct ep93xx_tcu *tcu = ep93xx_tcu;
+ struct clock_event_device *evt = dev_id;
+
+ /* Writing any value clears the timer interrupt */
+ writel(1, tcu->base + EP93XX_TIMER3_CLEAR);
+
+ evt->event_handler(evt);
+
+ return IRQ_HANDLED;
+}
+
+static int __init ep93xx_timer_of_init(struct device_node *np)
+{
+ int irq;
+ unsigned long flags = IRQF_TIMER | IRQF_IRQPOLL;
+ struct ep93xx_tcu *tcu;
+ int ret;
+
+ tcu = kzalloc(sizeof(*tcu), GFP_KERNEL);
+ if (!tcu)
+ return -ENOMEM;
+
+ tcu->base = of_iomap(np, 0);
+ if (!tcu->base) {
+ pr_err("Can't remap registers\n");
+ ret = -ENXIO;
+ goto out_free;
+ }
+
+ ep93xx_tcu = tcu;
+
+ irq = irq_of_parse_and_map(np, 0);
+ if (irq == 0)
+ irq = -EINVAL;
+ if (irq < 0) {
+ pr_err("EP93XX Timer Can't parse IRQ %d", irq);
+ goto out_free;
+ }
+
+ /* Enable and register clocksource and sched_clock on timer 4 */
+ writel(EP93XX_TIMER4_VALUE_HIGH_ENABLE,
+ tcu->base + EP93XX_TIMER4_VALUE_HIGH);
+ clocksource_mmio_init(NULL, "timer4",
+ EP93XX_TIMER4_RATE, 200, 40,
+ ep93xx_clocksource_read);
return code check
+ sched_clock_register(ep93xx_read_sched_clock, 40,
+ EP93XX_TIMER4_RATE);
+
+ /* Set up clockevent on timer 3 */
+ if (request_irq(irq, ep93xx_timer_interrupt, flags, "ep93xx timer",
+ &ep93xx_clockevent))
+ pr_err("Failed to request irq %d (ep93xx timer)\n", irq);
return error
+ clockevents_config_and_register(&ep93xx_clockevent,
+ EP93XX_TIMER123_RATE,
+ 1,
+ UINT_MAX);
+
+ return 0;
+
+out_free:
+ kfree(tcu);
+ return ret;
+}
+TIMER_OF_DECLARE(ep93xx_timer, "cirrus,ep9301-timer", ep93xx_timer_of_init);
--
<http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs
Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog