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-rw-r--r--arch/x86/include/asm/mach_timer.h49
1 files changed, 49 insertions, 0 deletions
diff --git a/arch/x86/include/asm/mach_timer.h b/arch/x86/include/asm/mach_timer.h
new file mode 100644
index 000000000..044daf6fb
--- /dev/null
+++ b/arch/x86/include/asm/mach_timer.h
@@ -0,0 +1,49 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Machine specific calibrate_tsc() for generic.
+ * Split out from timer_tsc.c by Osamu Tomita <tomita@cinet.co.jp>
+ */
+/* ------ Calibrate the TSC -------
+ * Return 2^32 * (1 / (TSC clocks per usec)) for do_fast_gettimeoffset().
+ * Too much 64-bit arithmetic here to do this cleanly in C, and for
+ * accuracy's sake we want to keep the overhead on the CTC speaker (channel 2)
+ * output busy loop as low as possible. We avoid reading the CTC registers
+ * directly because of the awkward 8-bit access mechanism of the 82C54
+ * device.
+ */
+#ifndef _ASM_X86_MACH_DEFAULT_MACH_TIMER_H
+#define _ASM_X86_MACH_DEFAULT_MACH_TIMER_H
+
+#define CALIBRATE_TIME_MSEC 30 /* 30 msecs */
+#define CALIBRATE_LATCH \
+ ((PIT_TICK_RATE * CALIBRATE_TIME_MSEC + 1000/2)/1000)
+
+static inline void mach_prepare_counter(void)
+{
+ /* Set the Gate high, disable speaker */
+ outb((inb(0x61) & ~0x02) | 0x01, 0x61);
+
+ /*
+ * Now let's take care of CTC channel 2
+ *
+ * Set the Gate high, program CTC channel 2 for mode 0,
+ * (interrupt on terminal count mode), binary count,
+ * load 5 * LATCH count, (LSB and MSB) to begin countdown.
+ *
+ * Some devices need a delay here.
+ */
+ outb(0xb0, 0x43); /* binary, mode 0, LSB/MSB, Ch 2 */
+ outb_p(CALIBRATE_LATCH & 0xff, 0x42); /* LSB of count */
+ outb_p(CALIBRATE_LATCH >> 8, 0x42); /* MSB of count */
+}
+
+static inline void mach_countup(unsigned long *count_p)
+{
+ unsigned long count = 0;
+ do {
+ count++;
+ } while ((inb_p(0x61) & 0x20) == 0);
+ *count_p = count;
+}
+
+#endif /* _ASM_X86_MACH_DEFAULT_MACH_TIMER_H */