ath10k: Fix reported HT MCS rates with NSS > 1

[Peter Oh]

On 11/06/2017 01:02 AM, Sven Eckelmann wrote:
> On Montag, 6. November 2017 09:28:42 CET Sebastian Gottschall wrote:
>> Am 06.11.2017 um 09:23 schrieb Sven Eckelmann:
>>> On Sonntag, 5. November 2017 10:22:22 CET Sebastian Gottschall wrote:
>>>> the assumption made in this patch is obviously wrong (at least for more
>>>> recent firmwares and 9984)
>>>> my log is flooded with messages like
>>>> [208802.803537] ath10k_pci 0001:03:00.0: Invalid VHT mcs 15 peer stats
>>>> [208805.108515] ath10k_pci 0001:03:00.0: Invalid VHT mcs 15 peer stats
>>>> [208821.747621] ath10k_pci 0001:03:00.0: Invalid VHT mcs 15 peer stats
>>>> [208822.516599] ath10k_pci 0001:03:00.0: Invalid VHT mcs 15 peer stats
>>>> [208841.257780] ath10k_pci 0001:03:00.0: Invalid VHT mcs 15 peer stats
> [...]
>>> This patch only splits WMI_RATE_PREAMBLE_HT & WMI_RATE_PREAMBLE_VHT. And for
>>> WMI_RATE_PREAMBLE_HT (*not VHT*), it uses a slightly different approach. But
>>> the WMI_RATE_PREAMBLE_VHT part (which you see in your logs) is basically
>>> untouched.
>> then a question follows up. is this check really neccessary?
> Until we find out what the heck VHT MCS 15 should mean in this context - maybe.
> But to the message - no, the message is most likely not necessary for each
> received "invalid" peer tx stat.
This validation check expects peer tx stat packets from FW contain 
reasonable values and gives warning if values are different from 
expectation. The problem comes from the assumption that "it always 
contains reasonable stat value" which is wrong at least based on my 
results. For instance, the reason MCS == 15 is because all 4 bits of mcs 
potion set to 1, not because FW really sets it to 15 intentionally. when 
the mcs potion bits are set to all 1s, the other bits such as nss are 
also set to all 1s.
Hence it looks FW passed totally invalid stat info to me.
I don't have preference on whether it's better to split VHT and HT check 
or not, but it is more appropriate to change that warning level to debug 
level.