firmware: fix duration of delay_us_at_mhz()
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@ -303,11 +303,11 @@ void delay(uint32_t duration)
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void delay_us_at_mhz(uint32_t us, uint32_t mhz)
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{
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// The loop below takes 4 cycles per iteration.
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uint32_t loop_iterations = (us * mhz) / 4;
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// The loop below takes 3 cycles per iteration.
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uint32_t loop_iterations = (us * mhz) / 3;
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asm volatile("start%=:\n"
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" subs %[ITERATIONS], #1\n" // 1 cycle
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" bpl start%=\n" // 3 cycles
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" bpl start%=\n" // 2 cycles
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:
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: [ITERATIONS] "r"(loop_iterations));
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}
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@ -560,7 +560,7 @@ static void cpu_clock_pll1_max_speed(void)
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CGU_BASE_M4_CLK = reg_val;
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/* 9. Wait 50us. */
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delay_us_at_mhz(50, 104);
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delay_us_at_mhz(50, 102);
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/* 10. Set the PLL1 P-divider to direct output mode (DIRECT=1). */
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CGU_PLL1_CTRL |= CGU_PLL1_CTRL_DIRECT_MASK;
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