On 07/11/2011 09:36 PM, Felix Fietkau wrote:
On 2011-07-11 8:52 AM, Michał Mirosław wrote:Also constify buf_addr for ath9k_hw_process_rxdesc_edma() to verify assumptions --- dma_sync_single_for_device() call can be removed. Signed-off-by: Michał Mirosław<mirq-linux@xxxxxxxxxxxx> --- drivers/net/wireless/ath/ath9k/ar9003_mac.c | 4 ++-- drivers/net/wireless/ath/ath9k/ar9003_mac.h | 2 +- drivers/net/wireless/ath/ath9k/recv.c | 10 +++------- 3 files changed, 6 insertions(+), 10 deletions(-) diff --git a/drivers/net/wireless/ath/ath9k/recv.c b/drivers/net/wireless/ath/ath9k/recv.c index 70dc8ec..c5f46d5 100644 --- a/drivers/net/wireless/ath/ath9k/recv.c +++ b/drivers/net/wireless/ath/ath9k/recv.c @@ -684,15 +684,11 @@ static bool ath_edma_get_buffers(struct ath_softc *sc, BUG_ON(!bf); dma_sync_single_for_cpu(sc->dev, bf->bf_buf_addr, - common->rx_bufsize, DMA_FROM_DEVICE); + common->rx_bufsize, DMA_BIDIRECTIONAL); ret = ath9k_hw_process_rxdesc_edma(ah, NULL, skb->data); - if (ret == -EINPROGRESS) { - /*let device gain the buffer again*/ - dma_sync_single_for_device(sc->dev, bf->bf_buf_addr, - common->rx_bufsize, DMA_FROM_DEVICE); + if (ret == -EINPROGRESS) return false; - } __skb_unlink(skb,&rx_edma->rx_fifo); if (ret == -EINVAL) {I have strong doubts about this change. On most MIPS devices, dma_sync_single_for_cpu is a no-op, whereas dma_sync_single_for_device flushes the cache range. With this change, the CPU could cache the DMA status part behind skb->data and that cache entry would not be flushed inbetween calls to this functions on the same buffer, likely leading to rx stalls.
At the very least, it would need heavy testing. It took a very long time to get the ath9k DMA issues (mostly?) resolved...so we shouldn't go mucking in this code on theory... Thanks, Ben
- Felix -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
-- Ben Greear <greearb@xxxxxxxxxxxxxxx> Candela Technologies Inc http://www.candelatech.com -- 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
