2013/5/5 Michael Büsch <m@xxxxxxx>: > On Sun, 5 May 2013 18:31:20 +0200 > Rafał Miłecki <zajec5@xxxxxxxxx> wrote: > >> Still worth considering is my previous e-mail. Why writing (for >> example) 1 to RXSTOPINDEX doesn't stop firmware from using slot 1? > > What makes you think this register does not work? Take a look at this: [ 327.224976] [DBG] old current:5 new current:6 [ 327.224982] [DBG] reading slot 5 [ 327.224997] [DBG] writing stop slot 6 In above ring->slot was 5, but IRQ was generated, and we read new "current" using get_current_rxslot. It appeared to be 6. So we read packet from slot 5 and then called ops->set_current_rxslot(ring, 6); AFAIU hardware shouldn't use slot 6, right? But take a look at what happens next: [ 327.319582] [DBG] old current:6 new current:7 [ 327.319590] [DBG] reading slot 6 [ 327.319619] [DBG] writing stop slot 7 Hardware generated IRQ and we get_current_rxslot returned 7. It means we're allowed to read slots up to 7 (excluding). It other words it means firmware used slot 6... but 100ms earlier we forbid firmware to use slot 6! This is part I don't understand. It looks like firmware ignores what we set with the ops->set_current_rxslot > Do you write a 1 to the register, or do you mean "the offset that > corresponds to slot 1"? I mean "the offset that corresponds to slot 1". In code it's: ops->set_current_rxslot(ring, 1); >> Can it be because it's "too late"? For example: >> 1) Firmware writes to slot 0, changes "curr descr" to 1 >> 2) Firmware grabs slot 1 >> 3) Firmware generates IRQ >> 4) Driver reads slot 0 >> 5) Driver writes RX stop index 1 > > The stop index is the index that the firmware does _not_ write to. > If you set it _after_ it already wrote, you clearly are too late (for > this ring wrapping). Take a look at above log. First we forbid firmware to use slot 6: [ 327.224997] [DBG] writing stop slot 6 but 100ms later firmware used that slot: [ 327.319582] [DBG] old current:6 new current:7 (it filled slot 6 and bumped value in B43_DMA64_RXSTATUS) -- Rafał -- 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
