diff options
Diffstat (limited to 'drivers/clocksource/bcm_kona_timer.c')
| -rw-r--r-- | drivers/clocksource/bcm_kona_timer.c | 202 |
1 files changed, 202 insertions, 0 deletions
diff --git a/drivers/clocksource/bcm_kona_timer.c b/drivers/clocksource/bcm_kona_timer.c new file mode 100644 index 000000000..a50ab5c21 --- /dev/null +++ b/drivers/clocksource/bcm_kona_timer.c @@ -0,0 +1,202 @@ +/* + * Copyright (C) 2012 Broadcom Corporation + * + * 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 version 2. + * + * This program is distributed "as is" WITHOUT ANY WARRANTY of any + * kind, whether express or implied; without even the implied warranty + * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + */ + +#include <linux/init.h> +#include <linux/irq.h> +#include <linux/interrupt.h> +#include <linux/jiffies.h> +#include <linux/clockchips.h> +#include <linux/types.h> +#include <linux/clk.h> + +#include <linux/io.h> + +#include <linux/of.h> +#include <linux/of_address.h> +#include <linux/of_irq.h> + + +#define KONA_GPTIMER_STCS_OFFSET 0x00000000 +#define KONA_GPTIMER_STCLO_OFFSET 0x00000004 +#define KONA_GPTIMER_STCHI_OFFSET 0x00000008 +#define KONA_GPTIMER_STCM0_OFFSET 0x0000000C + +#define KONA_GPTIMER_STCS_TIMER_MATCH_SHIFT 0 +#define KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT 4 + +struct kona_bcm_timers { + int tmr_irq; + void __iomem *tmr_regs; +}; + +static struct kona_bcm_timers timers; + +static u32 arch_timer_rate; + +/* + * We use the peripheral timers for system tick, the cpu global timer for + * profile tick + */ +static void kona_timer_disable_and_clear(void __iomem *base) +{ + uint32_t reg; + + /* + * clear and disable interrupts + * We are using compare/match register 0 for our system interrupts + */ + reg = readl(base + KONA_GPTIMER_STCS_OFFSET); + + /* Clear compare (0) interrupt */ + reg |= 1 << KONA_GPTIMER_STCS_TIMER_MATCH_SHIFT; + /* disable compare */ + reg &= ~(1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT); + + writel(reg, base + KONA_GPTIMER_STCS_OFFSET); + +} + +static int +kona_timer_get_counter(void __iomem *timer_base, uint32_t *msw, uint32_t *lsw) +{ + int loop_limit = 3; + + /* + * Read 64-bit free running counter + * 1. Read hi-word + * 2. Read low-word + * 3. Read hi-word again + * 4.1 + * if new hi-word is not equal to previously read hi-word, then + * start from #1 + * 4.2 + * if new hi-word is equal to previously read hi-word then stop. + */ + + do { + *msw = readl(timer_base + KONA_GPTIMER_STCHI_OFFSET); + *lsw = readl(timer_base + KONA_GPTIMER_STCLO_OFFSET); + if (*msw == readl(timer_base + KONA_GPTIMER_STCHI_OFFSET)) + break; + } while (--loop_limit); + if (!loop_limit) { + pr_err("bcm_kona_timer: getting counter failed.\n"); + pr_err(" Timer will be impacted\n"); + return -ETIMEDOUT; + } + + return 0; +} + +static int kona_timer_set_next_event(unsigned long clc, + struct clock_event_device *unused) +{ + /* + * timer (0) is disabled by the timer interrupt already + * so, here we reload the next event value and re-enable + * the timer. + * + * This way, we are potentially losing the time between + * timer-interrupt->set_next_event. CPU local timers, when + * they come in should get rid of skew. + */ + + uint32_t lsw, msw; + uint32_t reg; + int ret; + + ret = kona_timer_get_counter(timers.tmr_regs, &msw, &lsw); + if (ret) + return ret; + + /* Load the "next" event tick value */ + writel(lsw + clc, timers.tmr_regs + KONA_GPTIMER_STCM0_OFFSET); + + /* Enable compare */ + reg = readl(timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET); + reg |= (1 << KONA_GPTIMER_STCS_COMPARE_ENABLE_SHIFT); + writel(reg, timers.tmr_regs + KONA_GPTIMER_STCS_OFFSET); + + return 0; +} + +static int kona_timer_shutdown(struct clock_event_device *evt) +{ + kona_timer_disable_and_clear(timers.tmr_regs); + return 0; +} + +static struct clock_event_device kona_clockevent_timer = { + .name = "timer 1", + .features = CLOCK_EVT_FEAT_ONESHOT, + .set_next_event = kona_timer_set_next_event, + .set_state_shutdown = kona_timer_shutdown, + .tick_resume = kona_timer_shutdown, +}; + +static void __init kona_timer_clockevents_init(void) +{ + kona_clockevent_timer.cpumask = cpumask_of(0); + clockevents_config_and_register(&kona_clockevent_timer, + arch_timer_rate, 6, 0xffffffff); +} + +static irqreturn_t kona_timer_interrupt(int irq, void *dev_id) +{ + struct clock_event_device *evt = &kona_clockevent_timer; + + kona_timer_disable_and_clear(timers.tmr_regs); + evt->event_handler(evt); + return IRQ_HANDLED; +} + +static int __init kona_timer_init(struct device_node *node) +{ + u32 freq; + struct clk *external_clk; + + external_clk = of_clk_get_by_name(node, NULL); + + if (!IS_ERR(external_clk)) { + arch_timer_rate = clk_get_rate(external_clk); + clk_prepare_enable(external_clk); + } else if (!of_property_read_u32(node, "clock-frequency", &freq)) { + arch_timer_rate = freq; + } else { + pr_err("Kona Timer v1 unable to determine clock-frequency\n"); + return -EINVAL; + } + + /* Setup IRQ numbers */ + timers.tmr_irq = irq_of_parse_and_map(node, 0); + + /* Setup IO addresses */ + timers.tmr_regs = of_iomap(node, 0); + + kona_timer_disable_and_clear(timers.tmr_regs); + + kona_timer_clockevents_init(); + if (request_irq(timers.tmr_irq, kona_timer_interrupt, IRQF_TIMER, + "Kona Timer Tick", NULL)) + pr_err("%s: request_irq() failed\n", "Kona Timer Tick"); + kona_timer_set_next_event((arch_timer_rate / HZ), NULL); + + return 0; +} + +TIMER_OF_DECLARE(brcm_kona, "brcm,kona-timer", kona_timer_init); +/* + * bcm,kona-timer is deprecated by brcm,kona-timer + * being kept here for driver compatibility + */ +TIMER_OF_DECLARE(bcm_kona, "bcm,kona-timer", kona_timer_init); |