GK SDK 源码库: XMIPCLinuxV100R005C00SPC030 (kernel/tools/open_source excluded)

source/bootloader/u-boot-2020.01/arch/arm/cpu/armv8/generic_timer.c

@@ -0,0 +1,114 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * (C) Copyright 2013
+ * David Feng <fenghua@phytium.com.cn>
+ */
+
+#include <common.h>
+#include <command.h>
+#include <time.h>
+#include <asm/system.h>
+
+DECLARE_GLOBAL_DATA_PTR;
+
+/*
+ * Generic timer implementation of get_tbclk()
+ */
+unsigned long get_tbclk(void)
+{
+	unsigned long cntfrq;
+	asm volatile("mrs %0, cntfrq_el0" : "=r" (cntfrq));
+	return cntfrq;
+}
+
+#ifdef CONFIG_SYS_FSL_ERRATUM_A008585
+/*
+ * FSL erratum A-008585 says that the ARM generic timer counter "has the
+ * potential to contain an erroneous value for a small number of core
+ * clock cycles every time the timer value changes".
+ * This sometimes leads to a consecutive counter read returning a lower
+ * value than the previous one, thus reporting the time to go backwards.
+ * The workaround is to read the counter twice and only return when the value
+ * was the same in both reads.
+ * Assumes that the CPU runs in much higher frequency than the timer.
+ */
+unsigned long timer_read_counter(void)
+{
+	unsigned long cntpct;
+	unsigned long temp;
+
+	isb();
+	asm volatile("mrs %0, cntpct_el0" : "=r" (cntpct));
+	asm volatile("mrs %0, cntpct_el0" : "=r" (temp));
+	while (temp != cntpct) {
+		asm volatile("mrs %0, cntpct_el0" : "=r" (cntpct));
+		asm volatile("mrs %0, cntpct_el0" : "=r" (temp));
+	}
+
+	return cntpct;
+}
+#elif CONFIG_SUNXI_A64_TIMER_ERRATUM
+/*
+ * This erratum sometimes flips the lower 11 bits of the counter value
+ * to all 0's or all 1's, leading to jumps forwards or backwards.
+ * Backwards jumps might be interpreted all roll-overs and be treated as
+ * huge jumps forward.
+ * The workaround is to check whether the lower 11 bits of the counter are
+ * all 0 or all 1, then discard this value and read again.
+ * This occasionally discards valid values, but will catch all erroneous
+ * reads and fixes the problem reliably. Also this mostly requires only a
+ * single read, so does not have any significant overhead.
+ * The algorithm was conceived by Samuel Holland.
+ */
+unsigned long timer_read_counter(void)
+{
+	unsigned long cntpct;
+
+	isb();
+	do {
+		asm volatile("mrs %0, cntpct_el0" : "=r" (cntpct));
+	} while (((cntpct + 1) & GENMASK(10, 0)) <= 1);
+
+	return cntpct;
+}
+#else
+/*
+ * timer_read_counter() using the Arm Generic Timer (aka arch timer).
+ */
+unsigned long timer_read_counter(void)
+{
+	unsigned long cntpct;
+
+	isb();
+	asm volatile("mrs %0, cntpct_el0" : "=r" (cntpct));
+
+	return cntpct;
+}
+#endif
+
+uint64_t get_ticks(void)
+{
+	unsigned long ticks = timer_read_counter();
+
+	gd->arch.tbl = ticks;
+
+	return ticks;
+}
+
+unsigned long usec2ticks(unsigned long usec)
+{
+	ulong ticks;
+	if (usec < 1000)
+		ticks = ((usec * (get_tbclk()/1000)) + 500) / 1000;
+	else
+		ticks = ((usec / 10) * (get_tbclk() / 100000));
+
+	return ticks;
+}
+
+ulong timer_get_boot_us(void)
+{
+	u64 val = get_ticks() * 1000000;
+
+	return val / get_tbclk();
+}