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Date: Sun, 12 Apr 2015 03:31:15 -0700 From: Eric Dumazet <eric.dumazet@...il.com> To: Felix Fietkau <nbd@...nwrt.org> Cc: netdev@...r.kernel.org, zajec5@...il.com, hauke@...ke-m.de Subject: Re: [PATCH 4/4] bgmac: fix DMA rx corruption On Sun, 2015-04-12 at 12:08 +0200, Felix Fietkau wrote: > The driver needs to inform the hardware about the first invalid (not yet > filled) rx slot, by writing its DMA descriptor pointer offset to the > BGMAC_DMA_RX_INDEX register. > > This register was set to a value exceeding the rx ring size, effectively > allowing the hardware constant access to the full ring, regardless of > which slots are initialized. > > Fix this by updating the register in bgmac_dma_rx_setup_desc. > > Signed-off-by: Felix Fietkau <nbd@...nwrt.org> > --- > drivers/net/ethernet/broadcom/bgmac.c | 14 +++++++------- > 1 file changed, 7 insertions(+), 7 deletions(-) > > diff --git a/drivers/net/ethernet/broadcom/bgmac.c b/drivers/net/ethernet/broadcom/bgmac.c > index e332de8..856ceee 100644 > --- a/drivers/net/ethernet/broadcom/bgmac.c > +++ b/drivers/net/ethernet/broadcom/bgmac.c > @@ -380,6 +380,12 @@ static void bgmac_dma_rx_setup_desc(struct bgmac *bgmac, > dma_desc->addr_high = cpu_to_le32(upper_32_bits(ring->slots[desc_idx].dma_addr)); > dma_desc->ctl0 = cpu_to_le32(ctl0); > dma_desc->ctl1 = cpu_to_le32(ctl1); > + > + desc_idx = (desc_idx + 1) % BGMAC_RX_RING_SLOTS; > + > + bgmac_write(bgmac, ring->mmio_base + BGMAC_DMA_RX_INDEX, > + ring->index_base + > + desc_idx * sizeof(struct bgmac_dma_desc)); > } > > static int bgmac_dma_rx_read(struct bgmac *bgmac, struct bgmac_dma_ring *ring, > @@ -394,9 +400,7 @@ static int bgmac_dma_rx_read(struct bgmac *bgmac, struct bgmac_dma_ring *ring, > end_slot &= BGMAC_DMA_RX_STATDPTR; > end_slot /= sizeof(struct bgmac_dma_desc); > > - ring->end = end_slot; > - > - while (ring->start != ring->end) { > + while (ring->start != end_slot) { > struct device *dma_dev = bgmac->core->dma_dev; > struct bgmac_slot_info *slot = &ring->slots[ring->start]; > struct bgmac_rx_header *rx = slot->buf + BGMAC_RX_BUF_OFFSET; > @@ -693,10 +697,6 @@ static void bgmac_dma_init(struct bgmac *bgmac) > for (j = 0; j < ring->num_slots; j++) > bgmac_dma_rx_setup_desc(bgmac, ring, j); > Missing dma_wmb() here (or legacy wmb() for stable kernels) > - bgmac_write(bgmac, ring->mmio_base + BGMAC_DMA_RX_INDEX, > - ring->index_base + > - ring->num_slots * sizeof(struct bgmac_dma_desc)); > - This might be better for performance to perform one single bgmac_write() at the end of bgmac_dma_rx_read(), and leave this one in place as well, not for performance since this is slow path, but correctness. Also I am surprised there is no memory barrier to make sure changes to dma_desc are committed to memory ? I would use dma_wmb() before bgmac_write(), like the wmb() done in bgmac_dma_tx_add() Thanks -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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