MIPS: Loongson1B: Add a clockevent/clocksource using PWM Timer

This patch add a clockevent/clocksource using PWM Timer for Loongson1B,
which is based on earlier work by Tang, Haifeng.

Signed-off-by: Kelvin Cheung <keguang.zhang@gmail.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/8025/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

4 files changed, 266 insertions, 31 deletions

diff --git a/arch/mips/loongson1/Kconfig b/arch/mips/loongson1/Kconfig
index 4ed9744fe051..a2b796eaf3c3 100644
--- a/arch/mips/loongson1/Kconfig
+++ b/arch/mips/loongson1/Kconfig
@@ -5,8 +5,8 @@ choice
 
 config LOONGSON1_LS1B
         bool "Loongson LS1B board"
-        select CEVT_R4K
-        select CSRC_R4K
+        select CEVT_R4K if !MIPS_EXTERNAL_TIMER
+        select CSRC_R4K if !MIPS_EXTERNAL_TIMER
         select SYS_HAS_CPU_LOONGSON1B
         select DMA_NONCOHERENT
         select BOOT_ELF32
@@ -21,4 +21,41 @@ config LOONGSON1_LS1B
 
 endchoice
 
+menuconfig CEVT_CSRC_LS1X
+        bool "Use PWM Timer for clockevent/clocksource"
+        select MIPS_EXTERNAL_TIMER
+        depends on CPU_LOONGSON1
+        help
+          This option changes the default clockevent/clocksource to PWM Timer,
+          and is required by Loongson1 CPUFreq support.
+
+          If unsure, say N.
+
+choice
+        prompt  "Select clockevent/clocksource"
+        depends on CEVT_CSRC_LS1X
+        default TIMER_USE_PWM0
+
+config TIMER_USE_PWM0
+        bool "Use PWM Timer 0"
+        help
+          Use PWM Timer 0 as the default clockevent/clocksourcer.
+
+config TIMER_USE_PWM1
+        bool "Use PWM Timer 1"
+        help
+          Use PWM Timer 1 as the default clockevent/clocksourcer.
+
+config TIMER_USE_PWM2
+        bool "Use PWM Timer 2"
+        help
+          Use PWM Timer 2 as the default clockevent/clocksourcer.
+
+config TIMER_USE_PWM3
+        bool "Use PWM Timer 3"
+        help
+          Use PWM Timer 3 as the default clockevent/clocksourcer.
+
+endchoice
+
 endif # MACH_LOONGSON1
diff --git a/arch/mips/loongson1/common/Makefile b/arch/mips/loongson1/common/Makefile
index b2797709ef5b..723b4ce3b8f0 100644
--- a/arch/mips/loongson1/common/Makefile
+++ b/arch/mips/loongson1/common/Makefile
@@ -2,4 +2,4 @@
 # Makefile for common code of loongson1 based machines.
 #
 
-obj-y   += clock.o irq.o platform.o prom.o reset.o setup.o
+obj-y   += time.o irq.o platform.o prom.o reset.o setup.o
diff --git a/arch/mips/loongson1/common/clock.c b/arch/mips/loongson1/common/clock.c
deleted file mode 100644
index b4437f19c3d9..000000000000
--- a/arch/mips/loongson1/common/clock.c
+++ /dev/null
@@ -1,28 +0,0 @@
-/*
- * Copyright (c) 2011 Zhang, Keguang <keguang.zhang@gmail.com>
- *
- * This program is free software; you can redistribute  it and/or modify it
- * under  the terms of  the GNU General  Public License as published by the
- * Free Software Foundation;  either version 2 of the  License, or (at your
- * option) any later version.
- */
-
-#include <linux/clk.h>
-#include <linux/err.h>
-#include <asm/time.h>
-#include <platform.h>
-
-void __init plat_time_init(void)
-{
-        struct clk *clk;
-
-        /* Initialize LS1X clocks */
-        ls1x_clk_init();
-
-        /* setup mips r4k timer */
-        clk = clk_get(NULL, "cpu");
-        if (IS_ERR(clk))
-                panic("unable to get cpu clock, err=%ld", PTR_ERR(clk));
-
-        mips_hpt_frequency = clk_get_rate(clk) / 2;
-}
diff --git a/arch/mips/loongson1/common/time.c b/arch/mips/loongson1/common/time.c
new file mode 100644
index 000000000000..df0f850d6a5f
--- /dev/null
+++ b/arch/mips/loongson1/common/time.c
@@ -0,0 +1,226 @@
+/*
+ * Copyright (c) 2014 Zhang, Keguang <keguang.zhang@gmail.com>
+ *
+ * This program is free software; you can redistribute  it and/or modify it
+ * under  the terms of  the GNU General  Public License as published by the
+ * Free Software Foundation;  either version 2 of the  License, or (at your
+ * option) any later version.
+ */
+
+#include <linux/clk.h>
+#include <linux/interrupt.h>
+#include <asm/time.h>
+
+#include <loongson1.h>
+#include <platform.h>
+
+#ifdef CONFIG_CEVT_CSRC_LS1X
+
+#if defined(CONFIG_TIMER_USE_PWM1)
+#define LS1X_TIMER_BASE LS1X_PWM1_BASE
+#define LS1X_TIMER_IRQ  LS1X_PWM1_IRQ
+
+#elif defined(CONFIG_TIMER_USE_PWM2)
+#define LS1X_TIMER_BASE LS1X_PWM2_BASE
+#define LS1X_TIMER_IRQ  LS1X_PWM2_IRQ
+
+#elif defined(CONFIG_TIMER_USE_PWM3)
+#define LS1X_TIMER_BASE LS1X_PWM3_BASE
+#define LS1X_TIMER_IRQ  LS1X_PWM3_IRQ
+
+#else
+#define LS1X_TIMER_BASE LS1X_PWM0_BASE
+#define LS1X_TIMER_IRQ  LS1X_PWM0_IRQ
+#endif
+
+DEFINE_RAW_SPINLOCK(ls1x_timer_lock);
+
+static void __iomem *timer_base;
+static uint32_t ls1x_jiffies_per_tick;
+
+static inline void ls1x_pwmtimer_set_period(uint32_t period)
+{
+        __raw_writel(period, timer_base + PWM_HRC);
+        __raw_writel(period, timer_base + PWM_LRC);
+}
+
+static inline void ls1x_pwmtimer_restart(void)
+{
+        __raw_writel(0x0, timer_base + PWM_CNT);
+        __raw_writel(INT_EN | CNT_EN, timer_base + PWM_CTRL);
+}
+
+void __init ls1x_pwmtimer_init(void)
+{
+        timer_base = ioremap(LS1X_TIMER_BASE, 0xf);
+        if (!timer_base)
+                panic("Failed to remap timer registers");
+
+        ls1x_jiffies_per_tick = DIV_ROUND_CLOSEST(mips_hpt_frequency, HZ);
+
+        ls1x_pwmtimer_set_period(ls1x_jiffies_per_tick);
+        ls1x_pwmtimer_restart();
+}
+
+static cycle_t ls1x_clocksource_read(struct clocksource *cs)
+{
+        unsigned long flags;
+        int count;
+        u32 jifs;
+        static int old_count;
+        static u32 old_jifs;
+
+        raw_spin_lock_irqsave(&ls1x_timer_lock, flags);
+        /*
+         * Although our caller may have the read side of xtime_lock,
+         * this is now a seqlock, and we are cheating in this routine
+         * by having side effects on state that we cannot undo if
+         * there is a collision on the seqlock and our caller has to
+         * retry.  (Namely, old_jifs and old_count.)  So we must treat
+         * jiffies as volatile despite the lock.  We read jiffies
+         * before latching the timer count to guarantee that although
+         * the jiffies value might be older than the count (that is,
+         * the counter may underflow between the last point where
+         * jiffies was incremented and the point where we latch the
+         * count), it cannot be newer.
+         */
+        jifs = jiffies;
+        /* read the count */
+        count = __raw_readl(timer_base + PWM_CNT);
+
+        /*
+         * It's possible for count to appear to go the wrong way for this
+         * reason:
+         *
+         *  The timer counter underflows, but we haven't handled the resulting
+         *  interrupt and incremented jiffies yet.
+         *
+         * Previous attempts to handle these cases intelligently were buggy, so
+         * we just do the simple thing now.
+         */
+        if (count < old_count && jifs == old_jifs)
+                count = old_count;
+
+        old_count = count;
+        old_jifs = jifs;
+
+        raw_spin_unlock_irqrestore(&ls1x_timer_lock, flags);
+
+        return (cycle_t) (jifs * ls1x_jiffies_per_tick) + count;
+}
+
+static struct clocksource ls1x_clocksource = {
+        .name           = "ls1x-pwmtimer",
+        .read           = ls1x_clocksource_read,
+        .mask           = CLOCKSOURCE_MASK(24),
+        .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
+};
+
+static irqreturn_t ls1x_clockevent_isr(int irq, void *devid)
+{
+        struct clock_event_device *cd = devid;
+
+        ls1x_pwmtimer_restart();
+        cd->event_handler(cd);
+
+        return IRQ_HANDLED;
+}
+
+static void ls1x_clockevent_set_mode(enum clock_event_mode mode,
+                                     struct clock_event_device *cd)
+{
+        raw_spin_lock(&ls1x_timer_lock);
+        switch (mode) {
+        case CLOCK_EVT_MODE_PERIODIC:
+                ls1x_pwmtimer_set_period(ls1x_jiffies_per_tick);
+                ls1x_pwmtimer_restart();
+        case CLOCK_EVT_MODE_RESUME:
+                __raw_writel(INT_EN | CNT_EN, timer_base + PWM_CTRL);
+                break;
+        case CLOCK_EVT_MODE_ONESHOT:
+        case CLOCK_EVT_MODE_SHUTDOWN:
+                __raw_writel(__raw_readl(timer_base + PWM_CTRL) & ~CNT_EN,
+                             timer_base + PWM_CTRL);
+                break;
+        default:
+                break;
+        }
+        raw_spin_unlock(&ls1x_timer_lock);
+}
+
+static int ls1x_clockevent_set_next(unsigned long evt,
+                                    struct clock_event_device *cd)
+{
+        raw_spin_lock(&ls1x_timer_lock);
+        ls1x_pwmtimer_set_period(evt);
+        ls1x_pwmtimer_restart();
+        raw_spin_unlock(&ls1x_timer_lock);
+
+        return 0;
+}
+
+static struct clock_event_device ls1x_clockevent = {
+        .name           = "ls1x-pwmtimer",
+        .features       = CLOCK_EVT_FEAT_PERIODIC,
+        .rating         = 300,
+        .irq            = LS1X_TIMER_IRQ,
+        .set_next_event = ls1x_clockevent_set_next,
+        .set_mode       = ls1x_clockevent_set_mode,
+};
+
+static struct irqaction ls1x_pwmtimer_irqaction = {
+        .name           = "ls1x-pwmtimer",
+        .handler        = ls1x_clockevent_isr,
+        .dev_id         = &ls1x_clockevent,
+        .flags          = IRQF_PERCPU | IRQF_TIMER,
+};
+
+static void __init ls1x_time_init(void)
+{
+        struct clock_event_device *cd = &ls1x_clockevent;
+        int ret;
+
+        if (!mips_hpt_frequency)
+                panic("Invalid timer clock rate");
+
+        ls1x_pwmtimer_init();
+
+        clockevent_set_clock(cd, mips_hpt_frequency);
+        cd->max_delta_ns = clockevent_delta2ns(0xffffff, cd);
+        cd->min_delta_ns = clockevent_delta2ns(0x000300, cd);
+        cd->cpumask = cpumask_of(smp_processor_id());
+        clockevents_register_device(cd);
+
+        ls1x_clocksource.rating = 200 + mips_hpt_frequency / 10000000;
+        ret = clocksource_register_hz(&ls1x_clocksource, mips_hpt_frequency);
+        if (ret)
+                panic(KERN_ERR "Failed to register clocksource: %d\n", ret);
+
+        setup_irq(LS1X_TIMER_IRQ, &ls1x_pwmtimer_irqaction);
+}
+#endif /* CONFIG_CEVT_CSRC_LS1X */
+
+void __init plat_time_init(void)
+{
+        struct clk *clk = NULL;
+
+        /* initialize LS1X clocks */
+        ls1x_clk_init();
+
+#ifdef CONFIG_CEVT_CSRC_LS1X
+        /* setup LS1X PWM timer */
+        clk = clk_get(NULL, "ls1x_pwmtimer");
+        if (IS_ERR(clk))
+                panic("unable to get timer clock, err=%ld", PTR_ERR(clk));
+
+        mips_hpt_frequency = clk_get_rate(clk);
+        ls1x_time_init();
+#else
+        /* setup mips r4k timer */
+        clk = clk_get(NULL, "cpu_clk");
+        if (IS_ERR(clk))
+                panic("unable to get cpu clock, err=%ld", PTR_ERR(clk));
+
+        mips_hpt_frequency = clk_get_rate(clk) / 2;
+#endif /* CONFIG_CEVT_CSRC_LS1X */
+}