b070a03f64
Calculate core frequency from timers at boot time instead of assuming a fixed frequency. This is useful as the true frequency is set up by the boot loader, thus variable. Signed-off-by: Oskar Schirmer <os@emlix.com> Signed-off-by: Chris Zankel <chris@zankel.net>
27 lines
581 B
C
27 lines
581 B
C
#include <asm/delay.h>
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#include <asm/timex.h>
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#include <asm/io.h>
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#include <variant/hardware.h>
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#define LOOPS 10
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void platform_calibrate_ccount(void)
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{
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u32 uninitialized_var(a);
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u32 uninitialized_var(u);
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u32 b;
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u32 tstamp = S6_REG_GREG1 + S6_GREG1_GLOBAL_TIMER;
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int i = LOOPS+1;
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do {
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u32 t = u;
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asm volatile(
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"1: l32i %0, %2, 0 ;"
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" beq %0, %1, 1b ;"
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: "=&a"(u) : "a"(t), "a"(tstamp));
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b = xtensa_get_ccount();
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if (i == LOOPS)
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a = b;
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} while (--i >= 0);
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b -= a;
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nsec_per_ccount = (LOOPS * 10000) / b;
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ccount_per_jiffy = b * (100000UL / (LOOPS * HZ));
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}
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