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Message-ID: <1428862182.25985.354.camel@edumazet-glaptop2.roam.corp.google.com>
Date: Sun, 12 Apr 2015 11:09:42 -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 v2 4/4] bgmac: fix DMA rx corruption
On Sun, 2015-04-12 at 16:22 +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 | 27 ++++++++++++++++++---------
> 1 file changed, 18 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/net/ethernet/broadcom/bgmac.c b/drivers/net/ethernet/broadcom/bgmac.c
> index e332de8..67993d7 100644
> --- a/drivers/net/ethernet/broadcom/bgmac.c
> +++ b/drivers/net/ethernet/broadcom/bgmac.c
> @@ -362,6 +362,16 @@ static int bgmac_dma_rx_skb_for_slot(struct bgmac *bgmac,
> return 0;
> }
>
> +static void bgmac_dma_rx_update_index(struct bgmac *bgmac,
> + struct bgmac_dma_ring *ring)
> +{
> + dma_wmb();
> +
> + bgmac_write(bgmac, ring->mmio_base + BGMAC_DMA_RX_INDEX,
> + ring->index_base +
> + ring->end * sizeof(struct bgmac_dma_desc));
> +}
> +
> static void bgmac_dma_rx_setup_desc(struct bgmac *bgmac,
> struct bgmac_dma_ring *ring, int desc_idx)
> {
> @@ -380,6 +390,8 @@ 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);
> +
> + ring->end = (desc_idx + 1) % BGMAC_RX_RING_SLOTS;
Given the fact that previous driver kind of worked, have you tried not
doing the modulo at all here ?
ring->end = desc_idx + 1;
It looks like the hardware accepted setting BGMAC_DMA_RX_INDEX to
ring->index_base + ring->num_slots * sizeof(struct bgmac_dma_desc)
So apparently the presence of BGMAC_DESC_CTL0_EOT in last rx desc was
enough to avoid any problem with this.
Thanks
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