On Sun, 2010-02-28 at 23:08 +0100, Benoit Papillault wrote:
> - u64 tsf = ath5k_hw_reg_read(ah, AR5K_TSF_U32);
> + u32 tsf_lower, tsf_upper;
> +
> + /*
> + * While reading TSF upper and then lower part, the clock is still
> + * counting so the lower part can rollover just after reading the
> + * upper part. In this case, we expect the lower part to be quite
> + * small (let's say less than 100us) and we would just need to read
> + * the upper part again to get the correct value.
> + *
> + * Tested on AR2425 (AR5001)
> + */
> +
> + tsf_upper = ath5k_hw_reg_read(ah, AR5K_TSF_U32);
> + tsf_lower = ath5k_hw_reg_read(ah, AR5K_TSF_L32);
> +
> + if (tsf_lower < 100)
> + tsf_upper = ath5k_hw_reg_read(ah, AR5K_TSF_U32);
You would typically do
do {
read upper 1
read lower
read upper 2
} while (upper 1 != upper 2)
or so but that obviously incurs another read in most cases.
johannes
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