C-SKY(csky) Linux Kernel Drivers

From "PATCH V5 00/30] C-SKY(csky) Linux Kernel Port" I seperated the

This timer is used by SMP system and use mfcr/mtcr instruction to access the regs.

Changelog:
- Remove #define CPUHP_AP_CSKY_TIMER_STARTING
- Add CPUHP_AP_CSKY_TIMER_STARTING in cpuhotplug.h
- Support csky mp timer alpha version.
- Just use low-counter with 32bit width as clocksource.
- Coding convention with upstream feed-back.

Signed-off-by Guo Ren <[email protected]>

---
 drivers/clocksource/Kconfig        |   8 ++
 drivers/clocksource/Makefile       |   1 +
 drivers/clocksource/csky_mptimer.c | 176 +++++++++++++++++++++++++++++++++++++
 include/linux/cpuhotplug.h         |   1 +
 4 files changed, 186 insertions(+)
 create mode 100644 drivers/clocksource/csky_mptimer.c

drivers/clocksource/Kconfig +0 -0

index a11f4ba..a28043f 100644
@@ -620,4 +620,12 @@ config RISCV_TIMER
 	  is accessed via both the SBI and the rdcycle instruction.  This is
 	  required for all RISC-V systems.

drivers/clocksource/Makefile +1 -0

index db51b24..848c676 100644
@@ -79,3 +79,4 @@ obj-$(CONFIG_CLKSRC_ST_LPC)		+= clksrc_st_lpc.o
 obj-$(CONFIG_X86_NUMACHIP)		+= numachip.o
 obj-$(CONFIG_ATCPIT100_TIMER)		+= timer-atcpit100.o
 obj-$(CONFIG_RISCV_TIMER)		+= riscv_timer.o
+obj-$(CONFIG_CSKY_MPTIMER)		+= csky_mptimer.o

drivers/clocksource/csky_mptimer.c new file +49 -0

new file mode 100644
index 0000000..9dc3cfb
@@ -0,0 +1,176 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd.
+
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/sched_clock.h>
+#include <linux/cpu.h>
+#include <asm/reg_ops.h>
+
+#include "timer-of.h"
+
+#define PTIM_CCVR	"cr<3, 14>"
+#define PTIM_CTLR	"cr<0, 14>"
+#define PTIM_LVR	"cr<6, 14>"
+#define PTIM_TSR	"cr<1, 14>"
+
+static int csky_mptimer_set_next_event(unsigned long delta, struct clock_event_device *ce)
+{
+	mtcr(PTIM_LVR, delta);
+
+	return 0;
+}
+
+static int csky_mptimer_shutdown(struct clock_event_device *ce)
+{
+	mtcr(PTIM_CTLR, 0);
+
+	return 0;
+}
+
+static int csky_mptimer_oneshot(struct clock_event_device *ce)
+{
+	mtcr(PTIM_CTLR, 1);
+
+	return 0;
+}
+
+static int csky_mptimer_oneshot_stopped(struct clock_event_device *ce)
+{
+	mtcr(PTIM_CTLR, 0);
+
+	return 0;
+}
+
+static DEFINE_PER_CPU(struct timer_of, csky_to) = {
+	.flags					= TIMER_OF_CLOCK,
+	.clkevt = {
+		.rating				= 300,
+		.features			= CLOCK_EVT_FEAT_PERCPU |

drivers/clocksource/csky_mptimer.c new file +34 -0

+};
+
+static irqreturn_t timer_interrupt(int irq, void *dev)
+{
+	struct timer_of *to = this_cpu_ptr(&csky_to);
+
+	mtcr(PTIM_TSR, 0);
+
+	to->clkevt.event_handler(&to->clkevt);
+
+	return IRQ_HANDLED;
+}
+
+/*
+ * clock event for percpu
+ */
+static int csky_mptimer_starting_cpu(unsigned int cpu)
+{
+	struct timer_of *to = per_cpu_ptr(&csky_to, cpu);
+
+	to->clkevt.cpumask = cpumask_of(cpu);
+
+	clockevents_config_and_register(&to->clkevt, timer_of_rate(to), 2, ULONG_MAX);
+
+	enable_percpu_irq(timer_of_irq(to), 0);
+
+	return 0;
+}
+
+static int csky_mptimer_dying_cpu(unsigned int cpu)
+{
+	struct timer_of *to = per_cpu_ptr(&csky_to, cpu);
+
+	disable_percpu_irq(timer_of_irq(to));

drivers/clocksource/csky_mptimer.c new file +20 -0

+}
+
+struct clocksource csky_clocksource = {
+	.name	= "csky",
+	.rating	= 400,
+	.mask	= CLOCKSOURCE_MASK(32),
+	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
+	.read	= clksrc_read,
+};
+
+static int __init csky_mptimer_init(struct device_node *np)
+{
+	int ret, cpu;
+	struct timer_of *to;
+	int rate = 0;
+	int irq	 = 0;
+
+	/*
+	 * Csky_mptimer is designed for C-SKY SMP multi-processors and
+	 * every core has it's own private irq and regs for clkevt and

drivers/clocksource/csky_mptimer.c new file +12 -0

+	for_each_possible_cpu(cpu) {
+		to = per_cpu_ptr(&csky_to, cpu);
+
+		if (cpu == 0) {
+			to->flags	  |= TIMER_OF_IRQ;
+			to->of_irq.handler = timer_interrupt;
+
+			ret = timer_of_init(np, to);
+			if (ret)
+				return ret;
+
+			rate	= timer_of_rate(to);

drivers/clocksource/csky_mptimer.c new file +15 -0

+	ret = cpuhp_setup_state(CPUHP_AP_CSKY_TIMER_STARTING,
+				"clockevents/csky/timer:starting",
+				csky_mptimer_starting_cpu,
+				csky_mptimer_dying_cpu);
+	if (ret) {
+		pr_err("%s: Failed to cpuhp_setup_state.\n", __func__);
+		return ret;
+	}
+
+	clocksource_register_hz(&csky_clocksource, rate);
+	sched_clock_register(sched_clock_read, 32, rate);
+
+	return 0;
+}
+TIMER_OF_DECLARE(csky_mptimer, "csky,mptimer", csky_mptimer_init);

include/linux/cpuhotplug.h +1 -0

index caf40ad..e0cd2ba 100644
@@ -126,6 +126,7 @@ enum cpuhp_state {
 	CPUHP_AP_MIPS_GIC_TIMER_STARTING,
 	CPUHP_AP_ARC_TIMER_STARTING,
 	CPUHP_AP_RISCV_TIMER_STARTING,
+	CPUHP_AP_CSKY_TIMER_STARTING,
 	CPUHP_AP_KVM_STARTING,
 	CPUHP_AP_KVM_ARM_VGIC_INIT_STARTING,
 	CPUHP_AP_KVM_ARM_VGIC_STARTING,

Quoted 27 lines · Guo Ren

This timer is used by SMP system and use mfcr/mtcr instruction to access the regs.

Changelog:
- Remove #define CPUHP_AP_CSKY_TIMER_STARTING
- Add CPUHP_AP_CSKY_TIMER_STARTING in cpuhotplug.h
- Support csky mp timer alpha version.
- Just use low-counter with 32bit width as clocksource.
- Coding convention with upstream feed-back.

Signed-off-by Guo Ren <[email protected]>

---
 drivers/clocksource/Kconfig        |   8 ++
 drivers/clocksource/Makefile       |   1 +
 drivers/clocksource/csky_mptimer.c | 176 +++++++++++++++++++++++++++++++++++++
 include/linux/cpuhotplug.h         |   1 +
 4 files changed, 186 insertions(+)
 create mode 100644 drivers/clocksource/csky_mptimer.c

drivers/clocksource/Kconfig +0 -0

index a11f4ba..a28043f 100644
@@ -620,4 +620,12 @@ config RISCV_TIMER
 	  is accessed via both the SBI and the rdcycle instruction.  This is
 	  required for all RISC-V systems.
 

drivers/clocksource/Kconfig config RISCV_TIMER · line 631

Quoted 9 lines

drivers/clocksource/Kconfig +8 -0

+config CSKY_MPTIMER
+	bool "C-SKY Multi Processor Timer"
+	depends on CSKY
+	select TIMER_OF
+	help
+	  Say yes here to enable C-SKY SMP timer driver used for C-SKY SMP
+	  system.
+
 endmenu

The same rule applies here for COMPILE_TEST.

And please rename the file: timer-mp-csky.c

drivers/clocksource/Kconfig

Quoted 1 line

drivers/clocksource/Kconfig +1 -0

+	return (u64) mfcr(PTIM_CCVR);

extra space

drivers/clocksource/Kconfig

Quoted 6 lines

drivers/clocksource/Kconfig +5 -0

+}
+
+static u64 clksrc_read(struct clocksource *c)
+{
+	return (u64) mfcr(PTIM_CCVR);

extra space

drivers/clocksource/Kconfig

Quoted 2 lines

drivers/clocksource/Kconfig +2 -0

+	 */
+

extra line

Quoted 13 lines

drivers/clocksource/Kconfig +12 -0

+	for_each_possible_cpu(cpu) {
+		to = per_cpu_ptr(&csky_to, cpu);
+
+		if (cpu == 0) {
+			to->flags	  |= TIMER_OF_IRQ;
+			to->of_irq.handler = timer_interrupt;
+
+			ret = timer_of_init(np, to);
+			if (ret)
+				return ret;
+
+			rate	= timer_of_rate(to);

drivers/clocksource/Kconfig

Quoted 10 lines

drivers/clocksource/Kconfig +10 -0

+			irq	= to->of_irq.irq;
+		} else {
+			ret = timer_of_init(np, to);
+			if (ret)
+				return ret;
+
+			to->of_clk.rate	= rate;
+			to->of_irq.irq	= irq;
+		}
+	}

Isn't possible to replace this loop which is a bit confusing by:

- no irq flag specified for timer-of
- request irq before

So we end up with:

	irq = irq_of_parse_and_map(np, 0);
	if (irq <= 0)
		return -EINVAL;

ret = request_irq(irq, csky_timer_interrupt,
IRQF_TIMER | IRQF_PERCPU, "csky_mp_timer", &csky_to));

	if (ret)
		return ret;

	for_each_possible_cpu(cpu) {
		to = per_cpu_ptr(&csky_to, cpu);
		ret = timer_of_init(np, to);
		if (ret)
			goto rollback;

	}

Quoted 4 lines

	irq = irq_of_parse_and_map(np, 0);
	if (irq <= 0)
		return -EINVAL;

		panic();

I want a panic here. Return will make debug confused and directly tell the people where is wrong. It's root-timer for us and it must bootup.

If it's a co-timer, I also think return is good.

On 02/10/2018 07:40, Guo Ren wrote:
[ ... ]

Quoted 9 lines

Quoted 4 lines

	irq = irq_of_parse_and_map(np, 0);
	if (irq <= 0)
		return -EINVAL;

		panic();

I want a panic here. Return will make debug confused and directly tell the people where is wrong. It's root-timer for us and it must bootup.

If it's a co-timer, I also think return is good.

We don't need a panic in case of failure. If the board as an alternate timer it should be able to boot, that is the general rule of thumb for these drivers in this directory.

The init timer functions will be called via the timer_probe() which browse the timer_of_table (the one with all entries for the TIMER_OF_DECLARE macros).

You can see in the code below (from timer_probe.c), there is an error message emitted if the driver fails to initialize and another one much stronger if no timer was initialize.

This is enough trace IMO.

void __init timer_probe(void)

{
        struct device_node *np;
        const struct of_device_id *match;
        of_init_fn_1_ret init_func_ret;
        unsigned timers = 0;
        int ret;

        for_each_matching_node_and_match(np, __timer_of_table, &match) {
                if (!of_device_is_available(np))
                        continue;

                init_func_ret = match->data;

                ret = init_func_ret(np);
                if (ret) {
                        pr_err("Failed to initialize '%pOF': %d\n", np,
ret);
                        continue;
                }

                timers++;