diff options
Diffstat (limited to 'drivers/clocksource')
| -rw-r--r-- | drivers/clocksource/Kconfig | 1 | ||||
| -rw-r--r-- | drivers/clocksource/exynos_mct.c | 39 |
2 files changed, 33 insertions, 7 deletions
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig index 7ea7d7c48d72..cfd6519df661 100644 --- a/drivers/clocksource/Kconfig +++ b/drivers/clocksource/Kconfig @@ -127,6 +127,7 @@ config CLKSRC_METAG_GENERIC config CLKSRC_EXYNOS_MCT def_bool y if ARCH_EXYNOS + depends on !ARM64 help Support for Multi Core Timer controller on Exynos SoCs. diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c index 2df03e238c1b..9403061a2acc 100644 --- a/drivers/clocksource/exynos_mct.c +++ b/drivers/clocksource/exynos_mct.c @@ -162,7 +162,17 @@ static void exynos4_mct_frc_start(void) exynos4_mct_write(reg, EXYNOS4_MCT_G_TCON); } -static cycle_t notrace _exynos4_frc_read(void) +/** + * exynos4_read_count_64 - Read all 64-bits of the global counter + * + * This will read all 64-bits of the global counter taking care to make sure + * that the upper and lower half match. Note that reading the MCT can be quite + * slow (hundreds of nanoseconds) so you should use the 32-bit (lower half + * only) version when possible. + * + * Returns the number of cycles in the global counter. + */ +static u64 exynos4_read_count_64(void) { unsigned int lo, hi; u32 hi2 = readl_relaxed(reg_base + EXYNOS4_MCT_G_CNT_U); @@ -176,9 +186,22 @@ static cycle_t notrace _exynos4_frc_read(void) return ((cycle_t)hi << 32) | lo; } +/** + * exynos4_read_count_32 - Read the lower 32-bits of the global counter + * + * This will read just the lower 32-bits of the global counter. This is marked + * as notrace so it can be used by the scheduler clock. + * + * Returns the number of cycles in the global counter (lower 32 bits). + */ +static u32 notrace exynos4_read_count_32(void) +{ + return readl_relaxed(reg_base + EXYNOS4_MCT_G_CNT_L); +} + static cycle_t exynos4_frc_read(struct clocksource *cs) { - return _exynos4_frc_read(); + return exynos4_read_count_32(); } static void exynos4_frc_resume(struct clocksource *cs) @@ -190,21 +213,23 @@ struct clocksource mct_frc = { .name = "mct-frc", .rating = 400, .read = exynos4_frc_read, - .mask = CLOCKSOURCE_MASK(64), + .mask = CLOCKSOURCE_MASK(32), .flags = CLOCK_SOURCE_IS_CONTINUOUS, .resume = exynos4_frc_resume, }; static u64 notrace exynos4_read_sched_clock(void) { - return _exynos4_frc_read(); + return exynos4_read_count_32(); } static struct delay_timer exynos4_delay_timer; static cycles_t exynos4_read_current_timer(void) { - return _exynos4_frc_read(); + BUILD_BUG_ON_MSG(sizeof(cycles_t) != sizeof(u32), + "cycles_t needs to move to 32-bit for ARM64 usage"); + return exynos4_read_count_32(); } static void __init exynos4_clocksource_init(void) @@ -218,7 +243,7 @@ static void __init exynos4_clocksource_init(void) if (clocksource_register_hz(&mct_frc, clk_rate)) panic("%s: can't register clocksource\n", mct_frc.name); - sched_clock_register(exynos4_read_sched_clock, 64, clk_rate); + sched_clock_register(exynos4_read_sched_clock, 32, clk_rate); } static void exynos4_mct_comp0_stop(void) @@ -245,7 +270,7 @@ static void exynos4_mct_comp0_start(enum clock_event_mode mode, exynos4_mct_write(cycles, EXYNOS4_MCT_G_COMP0_ADD_INCR); } - comp_cycle = exynos4_frc_read(&mct_frc) + cycles; + comp_cycle = exynos4_read_count_64() + cycles; exynos4_mct_write((u32)comp_cycle, EXYNOS4_MCT_G_COMP0_L); exynos4_mct_write((u32)(comp_cycle >> 32), EXYNOS4_MCT_G_COMP0_U); |