Message-Id: <20250321134633.2155141-6-cjd@cjdns.fr>
Date: Fri, 21 Mar 2025 13:46:30 +0000
From: Caleb James DeLisle <cjd@...ns.fr>
To: linux-mips@...r.kernel.org
Cc: Thomas Gleixner <tglx@...utronix.de>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	benjamin.larsson@...exis.eu,
	Caleb James DeLisle <cjd@...ns.fr>
Subject: [PATCH v1 5/8] clocksource/drivers: Add EcoNet Timer HPT driver

Introduce a clocksource driver for the so-called high-precision timer (HPT)
in the EcoNet EN751221 MIPS SoC.

Signed-off-by: Caleb James DeLisle <cjd@...ns.fr>
---
The name HPT derives from a log line "Using XXX.XX MHz high precision timer"
which originated in mips/kernel/time.c and was copied into the vendor driver.
Subsequent generations of vendor and 3rd party out-of-tree drivers preserved
the log line long after it had been removed from the kernel proper. This
device began to be known as "the HPT", so we preserve the naming and log line.
---
 drivers/clocksource/Kconfig            |   8 +
 drivers/clocksource/Makefile           |   1 +
 drivers/clocksource/timer-econet-hpt.c | 221 +++++++++++++++++++++++++
 3 files changed, 230 insertions(+)
 create mode 100644 drivers/clocksource/timer-econet-hpt.c

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 487c85259967..1a7a9b4f16f9 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -73,6 +73,14 @@ config DW_APB_TIMER_OF
 	select DW_APB_TIMER
 	select TIMER_OF
 
+config ECONET_TIMER_HPT
+	bool "EcoNet High Precision Timer" if COMPILE_TEST
+	depends on HAS_IOMEM
+	select CLKSRC_MMIO
+	select TIMER_OF
+	help
+	  Support for CPU timer found on EcoNet MIPS based SoCs.
+
 config FTTMR010_TIMER
 	bool "Faraday Technology timer driver" if COMPILE_TEST
 	depends on HAS_IOMEM
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index 43ef16a4efa6..a3dd2a9d2a37 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -17,6 +17,7 @@ obj-$(CONFIG_CLKBLD_I8253)	+= i8253.o
 obj-$(CONFIG_CLKSRC_MMIO)	+= mmio.o
 obj-$(CONFIG_DAVINCI_TIMER)	+= timer-davinci.o
 obj-$(CONFIG_DIGICOLOR_TIMER)	+= timer-digicolor.o
+obj-$(CONFIG_ECONET_TIMER_HPT)	+= timer-econet-hpt.o
 obj-$(CONFIG_OMAP_DM_TIMER)	+= timer-ti-dm.o
 obj-$(CONFIG_OMAP_DM_SYSTIMER)	+= timer-ti-dm-systimer.o
 obj-$(CONFIG_DW_APB_TIMER)	+= dw_apb_timer.o
diff --git a/drivers/clocksource/timer-econet-hpt.c b/drivers/clocksource/timer-econet-hpt.c
new file mode 100644
index 000000000000..defd797426c5
--- /dev/null
+++ b/drivers/clocksource/timer-econet-hpt.c
@@ -0,0 +1,221 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Timer present on EcoNet EN75xx MIPS based SoCs.
+ *
+ * Copyright (C) 2025 by Caleb James DeLisle <cjd@...ns.fr>
+ */
+
+#include <linux/io.h>
+#include <linux/cpumask.h>
+#include <linux/interrupt.h>
+#include <linux/clockchips.h>
+#include <linux/sched_clock.h>
+#include <linux/of.h>
+#include <linux/of_irq.h>
+#include <linux/of_address.h>
+#include <linux/cpuhotplug.h>
+#include <linux/clk.h>
+
+#define ECONET_BITS			32
+#define ECONET_MIN_DELTA		0x00001000
+#define ECONET_MAX_DELTA		GENMASK(ECONET_BITS - 2, 0)
+/* 34Kc hardware has 1 block and 1004Kc has 2. */
+#define ECONET_NUM_BLOCKS		DIV_ROUND_UP(NR_CPUS, 2)
+
+static struct {
+	void __iomem *membase[ECONET_NUM_BLOCKS];
+	u32 freq_hz;
+} econet_timer __ro_after_init;
+
+static DEFINE_PER_CPU(struct clock_event_device, econet_timer_pcpu_m);
+
+/* Each memory block has 2 timers, the order of registers is:
+ * CTL, CMR0, CNT0, CMR1, CNT1
+ */
+static inline void __iomem *reg_ctl(u32 timer_n)
+{
+	return econet_timer.membase[timer_n >> 1];
+}
+
+static inline void __iomem *reg_compare(u32 timer_n)
+{
+	return econet_timer.membase[timer_n >> 1] + (timer_n & 1) * 0x08 + 0x04;
+}
+
+static inline void __iomem *reg_count(u32 timer_n)
+{
+	return econet_timer.membase[timer_n >> 1] + (timer_n & 1) * 0x08 + 0x08;
+}
+
+static inline u32 ctl_bit_enabled(u32 timer_n)
+{
+	return 1U << (timer_n & 1);
+}
+
+static inline u32 ctl_bit_pending(u32 timer_n)
+{
+	return 1U << ((timer_n & 1) + 16);
+}
+
+static bool cevt_is_pending(int cpu_id)
+{
+	return ioread32(reg_ctl(cpu_id)) & ctl_bit_pending(cpu_id);
+}
+
+static irqreturn_t cevt_interrupt(int irq, void *dev_id)
+{
+	struct clock_event_device *dev = this_cpu_ptr(&econet_timer_pcpu_m);
+	int cpu = cpumask_first(dev->cpumask);
+
+	if (!cevt_is_pending(cpu)) {
+		pr_debug("%s IRQ %d on CPU %d is not pending\n", __func__, irq, cpu);
+		return IRQ_NONE;
+	}
+
+	iowrite32(ioread32(reg_count(cpu)), reg_compare(cpu));
+	dev->event_handler(dev);
+	return IRQ_HANDLED;
+}
+
+static int cevt_set_next_event(ulong delta, struct clock_event_device *dev)
+{
+	int cpu;
+	u32 next;
+
+	cpu = cpumask_first(dev->cpumask);
+	next = ioread32(reg_count(cpu)) + delta;
+	iowrite32(next, reg_compare(cpu));
+
+	if ((s32)(next - ioread32(reg_count(cpu))) < ECONET_MIN_DELTA / 2)
+		return -ETIME;
+
+	return 0;
+}
+
+static int cevt_init_cpu(uint cpu)
+{
+	u32 reg;
+	struct clock_event_device *cd = &per_cpu(econet_timer_pcpu_m, cpu);
+
+	pr_info("%s: Setting up clockevent for CPU %d\n", cd->name, cpu);
+
+	reg = ioread32(reg_ctl(cpu)) | ctl_bit_enabled(cpu);
+	iowrite32(reg, reg_ctl(cpu));
+
+	enable_percpu_irq(cd->irq, IRQ_TYPE_NONE);
+
+	/* Do this last because it synchronously configures the timer */
+	clockevents_config_and_register(
+		cd, econet_timer.freq_hz,
+		ECONET_MIN_DELTA, ECONET_MAX_DELTA);
+
+	return 0;
+}
+
+static u64 notrace sched_clock_read(void)
+{
+	/* Always read from clock zero no matter the CPU */
+	return (u64)ioread32(reg_count(0));
+}
+
+/* Init */
+
+static void __init cevt_dev_init(uint cpu)
+{
+	iowrite32(0, reg_count(cpu));
+	iowrite32(U32_MAX, reg_compare(cpu));
+}
+
+static int __init cevt_init(struct device_node *np)
+{
+	int i;
+	int irq;
+	int ret;
+
+	irq = irq_of_parse_and_map(np, 0);
+	if (irq <= 0) {
+		pr_err("%pOFn: irq_of_parse_and_map failed", np);
+		return -EINVAL;
+	}
+
+	ret = request_percpu_irq(
+		irq, cevt_interrupt,
+		np->name, &econet_timer_pcpu_m);
+
+	if (ret < 0) {
+		pr_err("%pOFn: IRQ %d setup failed (%d)\n", np, irq, ret);
+		goto err_unmap_irq;
+	}
+
+	for_each_possible_cpu(i) {
+		struct clock_event_device *cd = &per_cpu(econet_timer_pcpu_m, i);
+
+		cd->rating		= 310,
+		cd->features		= CLOCK_EVT_FEAT_ONESHOT |
+					  CLOCK_EVT_FEAT_C3STOP |
+					  CLOCK_EVT_FEAT_PERCPU;
+		cd->set_next_event	= cevt_set_next_event;
+		cd->irq			= irq;
+		cd->cpumask		= cpumask_of(i);
+		cd->name		= np->name;
+
+		cevt_dev_init(i);
+	}
+
+	cpuhp_setup_state(CPUHP_AP_MIPS_GIC_TIMER_STARTING,
+			  "clockevents/en75/timer:starting",
+			  cevt_init_cpu, NULL);
+	return 0;
+
+err_unmap_irq:
+	irq_dispose_mapping(irq);
+	return ret;
+}
+
+static int __init timer_init(struct device_node *np)
+{
+	int num_blocks = DIV_ROUND_UP(num_possible_cpus(), 2);
+	struct clk *clk;
+	int ret;
+
+	clk = of_clk_get(np, 0);
+	if (IS_ERR(clk)) {
+		pr_err("%pOFn: Failed to get CPU clock from DT %ld\n", np,
+		       PTR_ERR(clk));
+		return PTR_ERR(clk);
+	}
+
+	econet_timer.freq_hz = clk_get_rate(clk);
+
+	for (int i = 0; i < num_blocks; i++) {
+		econet_timer.membase[i] = of_iomap(np, i);
+		if (!econet_timer.membase[i]) {
+			pr_err("%pOFn: failed to map register [%d]\n", np, i);
+			return -ENXIO;
+		}
+	}
+
+	/* For clocksource purposes always read clock zero, whatever the CPU */
+	ret = clocksource_mmio_init(reg_count(0), np->name,
+				    econet_timer.freq_hz, 301, ECONET_BITS,
+				    clocksource_mmio_readl_up);
+	if (ret) {
+		pr_err("%pOFn: clocksource_mmio_init failed: %d", np, ret);
+		return ret;
+	}
+
+	ret = cevt_init(np);
+	if (ret < 0)
+		return ret;
+
+	sched_clock_register(sched_clock_read, ECONET_BITS,
+			     econet_timer.freq_hz);
+
+	pr_info("%pOFn: using %u.%03u MHz high precision timer\n", np,
+		econet_timer.freq_hz / 1000000,
+		(econet_timer.freq_hz / 1000) % 1000);
+
+	return 0;
+}
+
+TIMER_OF_DECLARE(econet_timer_hpt, "econet,timer-hpt", timer_init);
-- 
2.30.2

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