On 2016-01-31 23:24, Johannes Stezenbach wrote: > Hi Felix, > > I noticed in mt76x2_mac_poll_tx_status() you are reading > MT_TX_STAT_FIFO before reading MT_TX_STAT_FIFO_EXT, > however I have a hunch that reading MT_TX_STAT_FIFO clobbers > the corresponding MT_TX_STAT_FIFO_EXT since MT_TX_STAT_FIFO > has the valid bit, and both registers together seem to implement > reading a 64bit FIFO entry. I.e. you need to read > MT_TX_STAT_FIFO_EXT first otherwise you get a mix from > two FIFO entries. > > I played a bit with the vendor driver for the mt7610u > and confirmed that multiple reads from MT_TX_STAT_FIFO_EXT > return the same value until MT_TX_STAT_FIFO is read. > (Note the mt7610u vendor driver does not define FIFO_EXT_SUPPORT > but the FIFO seems to exist in hardware. The mt7612u vendor driver > code reads the MT_TX_STAT_FIFO_EXT first.) Hi Johannes, When I wrote that particular part of the code, I still had a lot of other bugs regarding aggregation and rate probing. Back then, somehow I got better results reading FIFO before FIFO_EXT. I just did a few experiments to not only verify that reading FIFO clobbers FIFO_EXT, but also to ensure that the data from reading FIFO_EXT first really belongs to the value read from FIFO. I tested this by checking if the MT_TXWI_PKTID_PROBE flag in the pktid field (in FIFO_EXT) corresponds to a different rate being selected. My test results pretty much confirm your findings, so I've committed and pushed a fix. Thanks, - Felix -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
