2016-04-26 16:09:52

by Krishna Chaitanya

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Subject: [RFC] Sampling Holes in Minstrel when VHT is enabled

Hi,

With the current design, occasionally we are seeing issues
where minstrel sends 3x3 rates for our 2x2 chip.

IMHO, couple of things can cause this

1) update_caps doesn't take local HW capabilities in to account

2) While calculating sample_idx, we use MCS_GROUP_RATES
which can cause a sampling hole.

For eg: if sample_idx: 78, group will be 7 it is HT
so rate_idx will be : 8 + (2-1) * 8 = 16 = 3x3 MCS0 20 MHz.

ideally we should add

a) local hw_checks and update groups.supported accordingly.

b) use the formula index % get_max_group_rates (or) replace all
instances of MCS_GROUP_RATES for HT with 8.
(in set_rate, get_sampling_rate etc..)


--
Thanks,
Regards,
Chaitanya T K.