rt2x00: Improve TX status entry validation
The TX_STA_FIFO contains some information for identifying a outgoing frame, however matching by WCID and ACK status is not sufficient to 100% identify the macthing queue_entry structure (containing the SKB buffer) which belongs to the status report. Within TX_STA_FIFO we have a 4-bit field named PACKETID, which is currently used to encode the queue id. The queue ID is however limited to values from 0 to 3, which means 2 bits are sufficient to encode the value. With the remaining 2 bits we can encode a partial queue_entry index number. The value of PACKETID is not allowed to become 0, with the queue ID ranging from 0 to 3, at least one of the bits for the entry identification must be 1. That leaves us with 3 possible values we can still encode in the bits. Altough this doesn't allow 100% accurate matching of the TX_STA_FIFO queue to a queue_entry structure, it at least improves the accuracy. This allows us to better detect if we have missed the TX_STA_FIFO report, which in turn reduces the number of watchdog warnings regarding the TX status timeout. Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com> Signed-off-by: John W. Linville <linville@tuxdriver.com>
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