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Diffstat (limited to '')
-rw-r--r-- | arch/mips/generic/board-ranchu.c | 89 |
1 files changed, 89 insertions, 0 deletions
diff --git a/arch/mips/generic/board-ranchu.c b/arch/mips/generic/board-ranchu.c new file mode 100644 index 000000000..a89aaad59 --- /dev/null +++ b/arch/mips/generic/board-ranchu.c @@ -0,0 +1,89 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * Support code for virtual Ranchu board for MIPS. + * + * Author: Miodrag Dinic <miodrag.dinic@mips.com> + */ + +#include <linux/of_address.h> +#include <linux/types.h> + +#include <asm/machine.h> +#include <asm/mipsregs.h> +#include <asm/time.h> + +#define GOLDFISH_TIMER_LOW 0x00 +#define GOLDFISH_TIMER_HIGH 0x04 + +static __init u64 read_rtc_time(void __iomem *base) +{ + u32 time_low; + u32 time_high; + + /* + * Reading the low address latches the high value + * as well so there is no fear that we may read + * inaccurate high value. + */ + time_low = readl(base + GOLDFISH_TIMER_LOW); + time_high = readl(base + GOLDFISH_TIMER_HIGH); + + return ((u64)time_high << 32) | time_low; +} + +static __init unsigned int ranchu_measure_hpt_freq(void) +{ + u64 rtc_start, rtc_current, rtc_delta; + unsigned int start, count; + struct device_node *np; + void __iomem *rtc_base; + + np = of_find_compatible_node(NULL, NULL, "google,goldfish-rtc"); + if (!np) + panic("%s(): Failed to find 'google,goldfish-rtc' dt node!", + __func__); + + rtc_base = of_iomap(np, 0); + if (!rtc_base) + panic("%s(): Failed to ioremap Goldfish RTC base!", __func__); + + /* + * Poll the nanosecond resolution RTC for one + * second to calibrate the CPU frequency. + */ + rtc_start = read_rtc_time(rtc_base); + start = read_c0_count(); + + do { + rtc_current = read_rtc_time(rtc_base); + rtc_delta = rtc_current - rtc_start; + } while (rtc_delta < NSEC_PER_SEC); + + count = read_c0_count() - start; + + /* + * Make sure the frequency will be a round number. + * Without this correction, the returned value may vary + * between subsequent emulation executions. + * + * TODO: Set this value using device tree. + */ + count += 5000; + count -= count % 10000; + + iounmap(rtc_base); + + return count; +} + +static const struct of_device_id ranchu_of_match[] __initconst = { + { + .compatible = "mti,ranchu", + }, + {} +}; + +MIPS_MACHINE(ranchu) = { + .matches = ranchu_of_match, + .measure_hpt_freq = ranchu_measure_hpt_freq, +}; |