[PATCH 06/43] clocksource: ep93xx: Add driver for Cirrus Logic EP93xx
From: Nikita Shubin
Date: Mon Apr 24 2023 - 05:55:51 EST
This us a rewrite of EP93xx timer driver 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.
Signed-off-by: Nikita Shubin <nikita.shubin@xxxxxxxxxxx>
---
drivers/clocksource/Kconfig | 11 ++
drivers/clocksource/Makefile | 1 +
drivers/clocksource/timer-ep93xx.c | 191 +++++++++++++++++++++++++++++
3 files changed, 203 insertions(+)
create mode 100644 drivers/clocksource/timer-ep93xx.c
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 5fc8f0e7fb38..40bfc7c86756 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -721,4 +721,15 @@ 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
+ depends on GENERIC_CLOCKEVENTS
+ 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 64ab547de97b..09c2d4e5d809 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -88,3 +88,4 @@ obj-$(CONFIG_MICROCHIP_PIT64B) += timer-microchip-pit64b.o
obj-$(CONFIG_MSC313E_TIMER) += timer-msc313e.o
obj-$(CONFIG_GOLDFISH_TIMER) += timer-goldfish.o
obj-$(CONFIG_GXP_TIMER) += timer-gxp.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..58dc15a21318
--- /dev/null
+++ b/drivers/clocksource/timer-ep93xx.c
@@ -0,0 +1,191 @@
+// 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/kernel.h>
+#include <linux/init.h>
+#include <linux/clocksource.h>
+#include <linux/clockchips.h>
+#include <linux/sched_clock.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/of_irq.h>
+#include <linux/of_address.h>
+#include <linux/io.h>
+#include <linux/regmap.h>
+#include <linux/mfd/syscon.h>
+#include <asm/mach/time.h>
+
+/*************************************************************************
+ * 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;
+
+static u64 ep93xx_clocksource_read(struct clocksource *c)
+{
+ struct ep93xx_tcu *tcu = ep93xx_tcu;
+ u64 ret;
+
+ ret = readl(tcu->base + EP93XX_TIMER4_VALUE_LOW);
+ ret |= ((u64) (readl(tcu->base + EP93XX_TIMER4_VALUE_HIGH) & 0xff) << 32);
+ return (u64) ret;
+}
+
+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) {
+ pr_err("ERROR: invalid interrupt number\n");
+ ret = -EINVAL;
+ 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);
+ 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);
+ clockevents_config_and_register(&ep93xx_clockevent,
+ EP93XX_TIMER123_RATE,
+ 1,
+ 0xffffffffU);
+
+ return 0;
+
+out_free:
+ kfree(tcu);
+ return ret;
+}
+
+TIMER_OF_DECLARE(ep93xx_timer, "cirrus,ep9301-timer", ep93xx_timer_of_init);
--
2.39.2