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ARM: mxs: spl_boot.c: make early_delay more robust
It's true that booting normally doesn't take long enough for the register to roll (which actually happens in a little over an hour, not just a few seconds). However, the counter starts at power-on, and if the board is held in reset to be booted over USB, one actually risks hitting wrap-around during boot, which can both result in too short delays (if the "st += delay" calculation makes st small) and theoretically also unbound delays (if st ends up being UINT_MAX and one just misses sampling digctl_microseconds at that point). It doesn't take more code to DTRT, and once bitten, twice shy. Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
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1 changed files with 2 additions and 5 deletions
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@ -25,9 +25,7 @@ static bd_t bdata __section(".data");
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/*
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* This delay function is intended to be used only in early stage of boot, where
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* clock are not set up yet. The timer used here is reset on every boot and
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* takes a few seconds to roll. The boot doesn't take that long, so to keep the
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* code simple, it doesn't take rolling into consideration.
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* clock are not set up yet.
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*/
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void early_delay(int delay)
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{
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@ -35,8 +33,7 @@ void early_delay(int delay)
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(struct mxs_digctl_regs *)MXS_DIGCTL_BASE;
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uint32_t st = readl(&digctl_regs->hw_digctl_microseconds);
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st += delay;
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while (st > readl(&digctl_regs->hw_digctl_microseconds))
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while (readl(&digctl_regs->hw_digctl_microseconds) - st <= delay)
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;
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}
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