[PATCH v2 6/8] clocksource: realtek: Add timer driver for rtl-otto platforms

Chris Packham
2024-06-24T01:23:17Z

The timer/counter block on the Realtek SoCs provides up to 5 timers. It
also includes a watchdog timer but this isn't being used currently (it
will be added as a separate wdt driver).

One timer will be used per CPU as a local clock event generator. An
additional timer will be used as an overal stable clocksource.

Signed-off-by: Markus Stockhausen <markus.stockhausen@gmx.de>
Signed-off-by: Sander Vanheule <sander@svanheule.net>
Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
---

Notes:
This is derrived from openwrt[1],[2]. I've retained the original signoff
and added my own.

[1] https://git.openwrt.org/?p=openwrt/openwrt.git;a=blob_plain;f=target/linux/realtek/files-5.15/drivers/clocksource/timer-rtl-otto.c;hb=HEAD
[2] https://git.openwrt.org/?p=openwrt/openwrt.git;a=blob_plain;f=target/linux/realtek/patches-5.15/302-clocksource-add-otto-driver.patch;hb=HEAD

drivers/clocksource/Kconfig | 11 +
drivers/clocksource/Makefile | 1 +
drivers/clocksource/timer-rtl-otto.c | 287 +++++++++++++++++++++++++++
include/linux/cpuhotplug.h | 1 +
4 files changed, 300 insertions(+)
create mode 100644 drivers/clocksource/timer-rtl-otto.c

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 34faa0320ece..f02b5b50d166 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -134,6 +134,17 @@ config RDA_TIMER
help
Enables the support for the RDA Micro timer driver.

+config REALTEK_OTTO_TIMER
+ bool "Clocksource/timer for the Realtek Otto platform"
+ select COMMON_CLK
+ select TIMER_OF
+ help
+ This driver adds support for the timers found in the Realtek RTL83xx
+ and RTL93xx SoCs series. This includes chips such as RTL8380, RTL8381
+ and RTL832, as well as chips from the RTL839x series, such as RTL8390
+ RT8391, RTL8392, RTL8393 and RTL8396 and chips of the RTL930x series
+ such as RTL9301, RTL9302 or RTL9303.
+
config SUN4I_TIMER
bool "Sun4i timer driver" if COMPILE_TEST
depends on HAS_IOMEM
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index 4bb856e4df55..22743785299e 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -59,6 +59,7 @@ obj-$(CONFIG_MILBEAUT_TIMER) += timer-milbeaut.o
obj-$(CONFIG_SPRD_TIMER) += timer-sprd.o
obj-$(CONFIG_NPCM7XX_TIMER) += timer-npcm7xx.o
obj-$(CONFIG_RDA_TIMER) += timer-rda.o
+obj-$(CONFIG_REALTEK_OTTO_TIMER) += timer-rtl-otto.o

obj-$(CONFIG_ARC_TIMERS) += arc_timer.o
obj-$(CONFIG_ARM_ARCH_TIMER) += arm_arch_timer.o
diff --git a/drivers/clocksource/timer-rtl-otto.c b/drivers/clocksource/timer-rtl-otto.c
new file mode 100644
index 000000000000..7e41ae95d7dc
--- /dev/null
+++ b/drivers/clocksource/timer-rtl-otto.c
@@ -0,0 +1,287 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/clk.h>
+#include <linux/clockchips.h>
+#include <linux/cpu.h>
+#include <linux/cpuhotplug.h>
+#include <linux/interrupt.h>
+#include <linux/sched_clock.h>
+#include "timer-of.h"
+
+#define RTTM_DATA 0x0
+#define RTTM_CNT 0x4
+#define RTTM_CTRL 0x8
+#define RTTM_INT 0xc
+
+#define RTTM_CTRL_ENABLE BIT(28)
+#define RTTM_INT_PENDING BIT(16)
+#define RTTM_INT_ENABLE BIT(20)
+
+/*
+ * The Otto platform provides multiple 28 bit timers/counters with the following
+ * operating logic. If enabled the timer counts up. Per timer one can set a
+ * maximum counter value as an end marker. If end marker is reached the timer
+ * fires an interrupt. If the timer "overflows" by reaching the end marker or
+ * by adding 1 to 0x0fffffff the counter is reset to 0. When this happens and
+ * the timer is in operating mode COUNTER it stops. In mode TIMER it will
+ * continue to count up.
+ */
+#define RTTM_CTRL_COUNTER 0
+#define RTTM_CTRL_TIMER BIT(24)
+
+#define RTTM_BIT_COUNT 28
+#define RTTM_MIN_DELTA 8
+#define RTTM_MAX_DELTA CLOCKSOURCE_MASK(28)
+
+/*
+ * Timers are derived from the LXB clock frequency. Usually this is a fixed
+ * multiple of the 25 MHz oscillator. The 930X SOC is an exception from that.
+ * Its LXB clock has only dividers and uses the switch PLL of 2.45 GHz as its
+ * base. The only meaningful frequencies we can achieve from that are 175.000
+ * MHz and 153.125 MHz. The greatest common divisor of all explained possible
+ * speeds is 3125000. Pin the timers to this 3.125 MHz reference frequency.
+ */
+#define RTTM_TICKS_PER_SEC 3125000
+
+struct rttm_cs {
+ struct timer_of to;
+ struct clocksource cs;
+};
+
+/* Simple internal register functions */
+static inline void rttm_set_counter(void __iomem *base, unsigned int counter)
+{
+ iowrite32(counter, base + RTTM_CNT);
+}
+
+static inline unsigned int rttm_get_counter(void __iomem *base)
+{
+ return ioread32(base + RTTM_CNT);
+}
+
+static inline void rttm_set_period(void __iomem *base, unsigned int period)
+{
+ iowrite32(period, base + RTTM_DATA);
+}
+
+static inline void rttm_disable_timer(void __iomem *base)
+{
+ iowrite32(0, base + RTTM_CTRL);
+}
+
+static inline void rttm_enable_timer(void __iomem *base, u32 mode, u32 divisor)
+{
+ iowrite32(RTTM_CTRL_ENABLE | mode | divisor, base + RTTM_CTRL);
+}
+
+static inline void rttm_ack_irq(void __iomem *base)
+{
+ iowrite32(ioread32(base + RTTM_INT) | RTTM_INT_PENDING, base + RTTM_INT);
+}
+
+static inline void rttm_enable_irq(void __iomem *base)
+{
+ iowrite32(RTTM_INT_ENABLE, base + RTTM_INT);
+}
+
+static inline void rttm_disable_irq(void __iomem *base)
+{
+ iowrite32(0, base + RTTM_INT);
+}
+
+/* Aggregated control functions for kernel clock framework */
+#define RTTM_DEBUG(base) \
+ pr_debug("------------- %d %08x\n", \
+ smp_processor_id(), (u32)base)
+
+static irqreturn_t rttm_timer_interrupt(int irq, void *dev_id)
+{
+ struct clock_event_device *clkevt = dev_id;
+ struct timer_of *to = to_timer_of(clkevt);
+
+ rttm_ack_irq(to->of_base.base);
+ RTTM_DEBUG(to->of_base.base);
+ clkevt->event_handler(clkevt);
+
+ return IRQ_HANDLED;
+}
+
+static void rttm_stop_timer(void __iomem *base)
+{
+ rttm_disable_timer(base);
+ rttm_ack_irq(base);
+}
+
+static void rttm_start_timer(struct timer_of *to, u32 mode)
+{
+ rttm_set_counter(to->of_base.base, 0);
+ rttm_enable_timer(to->of_base.base, mode, to->of_clk.rate / RTTM_TICKS_PER_SEC);
+}
+
+static int rttm_next_event(unsigned long delta, struct clock_event_device *clkevt)
+{
+ struct timer_of *to = to_timer_of(clkevt);
+
+ RTTM_DEBUG(to->of_base.base);
+ rttm_stop_timer(to->of_base.base);
+ rttm_set_period(to->of_base.base, delta);
+ rttm_start_timer(to, RTTM_CTRL_COUNTER);
+
+ return 0;
+}
+
+static int rttm_state_oneshot(struct clock_event_device *clkevt)
+{
+ struct timer_of *to = to_timer_of(clkevt);
+
+ RTTM_DEBUG(to->of_base.base);
+ rttm_stop_timer(to->of_base.base);
+ rttm_set_period(to->of_base.base, RTTM_TICKS_PER_SEC / HZ);
+ rttm_start_timer(to, RTTM_CTRL_COUNTER);
+
+ return 0;
+}
+
+static int rttm_state_periodic(struct clock_event_device *clkevt)
+{
+ struct timer_of *to = to_timer_of(clkevt);
+
+ RTTM_DEBUG(to->of_base.base);
+ rttm_stop_timer(to->of_base.base);
+ rttm_set_period(to->of_base.base, RTTM_TICKS_PER_SEC / HZ);
+ rttm_start_timer(to, RTTM_CTRL_TIMER);
+
+ return 0;
+}
+
+static int rttm_state_shutdown(struct clock_event_device *clkevt)
+{
+ struct timer_of *to = to_timer_of(clkevt);
+
+ RTTM_DEBUG(to->of_base.base);
+ rttm_stop_timer(to->of_base.base);
+
+ return 0;
+}
+
+static void rttm_setup_timer(void __iomem *base)
+{
+ RTTM_DEBUG(base);
+ rttm_stop_timer(base);
+ rttm_set_period(base, 0);
+}
+
+static u64 rttm_read_clocksource(struct clocksource *cs)
+{
+ struct rttm_cs *rcs = container_of(cs, struct rttm_cs, cs);
+
+ return (u64)rttm_get_counter(rcs->to.of_base.base);
+}
+
+/* Module initialization part. */
+static DEFINE_PER_CPU(struct timer_of, rttm_to) = {
+ .flags = TIMER_OF_BASE | TIMER_OF_CLOCK | TIMER_OF_IRQ,
+ .of_irq = {
+ .flags = IRQF_PERCPU | IRQF_TIMER,
+ .handler = rttm_timer_interrupt,
+ },
+ .clkevt = {
+ .rating = 400,
+ .features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT,
+ .set_state_periodic = rttm_state_periodic,
+ .set_state_shutdown = rttm_state_shutdown,
+ .set_state_oneshot = rttm_state_oneshot,
+ .set_next_event = rttm_next_event
+ },
+};
+
+static int rttm_enable_clocksource(struct clocksource *cs)
+{
+ struct rttm_cs *rcs = container_of(cs, struct rttm_cs, cs);
+
+ rttm_disable_irq(rcs->to.of_base.base);
+ rttm_setup_timer(rcs->to.of_base.base);
+ rttm_enable_timer(rcs->to.of_base.base, RTTM_CTRL_TIMER,
+ rcs->to.of_clk.rate / RTTM_TICKS_PER_SEC);
+
+ return 0;
+}
+
+struct rttm_cs rttm_cs = {
+ .to = {
+ .flags = TIMER_OF_BASE | TIMER_OF_CLOCK,
+ },
+ .cs = {
+ .name = "realtek_otto_timer",
+ .rating = 400,
+ .mask = CLOCKSOURCE_MASK(RTTM_BIT_COUNT),
+ .flags = CLOCK_SOURCE_IS_CONTINUOUS,
+ .read = rttm_read_clocksource,
+ }
+};
+
+static u64 notrace rttm_read_clock(void)
+{
+ return (u64)rttm_get_counter(rttm_cs.to.of_base.base);
+}
+
+static int rttm_cpu_starting(unsigned int cpu)
+{
+ struct timer_of *to = per_cpu_ptr(&rttm_to, cpu);
+
+ RTTM_DEBUG(to->of_base.base);
+ to->clkevt.cpumask = cpumask_of(cpu);
+ irq_force_affinity(to->of_irq.irq, to->clkevt.cpumask);
+ clockevents_config_and_register(&to->clkevt, RTTM_TICKS_PER_SEC,
+ RTTM_MIN_DELTA, RTTM_MAX_DELTA);
+ rttm_enable_irq(to->of_base.base);
+
+ return 0;
+}
+
+static int __init rttm_probe(struct device_node *np)
+{
+ int cpu, cpu_rollback;
+ struct timer_of *to;
+ int clkidx = num_possible_cpus();
+
+ /* Use the first n timers as per CPU clock event generators */
+ for_each_possible_cpu(cpu) {
+ to = per_cpu_ptr(&rttm_to, cpu);
+ to->of_irq.index = to->of_base.index = cpu;
+ if (timer_of_init(np, to)) {
+ pr_err("setup of timer %d failed\n", cpu);
+ goto rollback;
+ }
+ rttm_setup_timer(to->of_base.base);
+ }
+
+ /* Activate the n'th + 1 timer as a stable CPU clocksource. */
+ to = &rttm_cs.to;
+ to->of_base.index = clkidx;
+ timer_of_init(np, to);
+ if (rttm_cs.to.of_base.base && rttm_cs.to.of_clk.rate) {
+ rttm_enable_clocksource(&rttm_cs.cs);
+ clocksource_register_hz(&rttm_cs.cs, RTTM_TICKS_PER_SEC);
+ sched_clock_register(rttm_read_clock, RTTM_BIT_COUNT, RTTM_TICKS_PER_SEC);
+ } else
+ pr_err(" setup of timer %d as clocksource failed", clkidx);
+
+ return cpuhp_setup_state(CPUHP_AP_REALTEK_TIMER_STARTING,
+ "timer/realtek:online",
+ rttm_cpu_starting, NULL);
+rollback:
+ pr_err("timer registration failed\n");
+ for_each_possible_cpu(cpu_rollback) {
+ if (cpu_rollback == cpu)
+ break;
+ to = per_cpu_ptr(&rttm_to, cpu_rollback);
+ timer_of_cleanup(to);
+ }
+
+ return -EINVAL;
+}
+
+TIMER_OF_DECLARE(otto_timer, "realtek,otto-timer", rttm_probe);
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
index 7a5785f405b6..56b744dc1317 100644
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -171,6 +171,7 @@ enum cpuhp_state {
CPUHP_AP_ARMADA_TIMER_STARTING,
CPUHP_AP_MIPS_GIC_TIMER_STARTING,
CPUHP_AP_ARC_TIMER_STARTING,
+ CPUHP_AP_REALTEK_TIMER_STARTING,
CPUHP_AP_RISCV_TIMER_STARTING,
CPUHP_AP_CLINT_TIMER_STARTING,
CPUHP_AP_CSKY_TIMER_STARTING,
--
2.45.2