Christophe Leroy <christophe.le...@csgroup.eu> writes:
> Le 19/05/2022 à 21:24, Mans Rullgard a écrit :
>> The dma_sync_single_for_cpu() call must precede reading the received
>> data. Fix this.
>
> See original commit 070e1f01827c. It explicitely says that the cache
> must be invalidate _AFTER_ the copy.
>
> The cache is initialy invalidated by dma_map_single(), so before the
> copy the cache is already clean.
>
> After the copy, data is in the cache. In order to allow re-use of the
> skb, it must be put back in the same condition as before, in extenso the
> cache must be invalidated in order to be in the same situation as after
> dma_map_single().
>
> So I think your change is wrong.
OK, looking at it more closely, the change is at least unnecessary since
there will be a cache invalidation between each use of the buffer either
way. Please disregard the patch. Sorry for the noise.
>>
>> Fixes: 070e1f01827c ("net: fs_enet: don't unmap DMA when packet len is below
>> copybreak")
>> Signed-off-by: Mans Rullgard <m...@mansr.com>
>> ---
>> drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c | 8 ++++----
>> 1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c
>> b/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c
>> index b3dae17e067e..432ce10cbfd0 100644
>> --- a/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c
>> +++ b/drivers/net/ethernet/freescale/fs_enet/fs_enet-main.c
>> @@ -240,14 +240,14 @@ static int fs_enet_napi(struct napi_struct *napi, int
>> budget)
>> /* +2 to make IP header L1 cache aligned */
>> skbn = netdev_alloc_skb(dev, pkt_len + 2);
>> if (skbn != NULL) {
>> + dma_sync_single_for_cpu(fep->dev,
>> + CBDR_BUFADDR(bdp),
>> + L1_CACHE_ALIGN(pkt_len),
>> + DMA_FROM_DEVICE);
>> skb_reserve(skbn, 2); /* align IP
>> header */
>> skb_copy_from_linear_data(skb,
>> skbn->data, pkt_len);
>> swap(skb, skbn);
>> - dma_sync_single_for_cpu(fep->dev,
>> - CBDR_BUFADDR(bdp),
>> - L1_CACHE_ALIGN(pkt_len),
>> - DMA_FROM_DEVICE);
>> }
>> } else {
>> skbn = netdev_alloc_skb(dev,
>> ENET_RX_FRSIZE);
>> --
>> 2.35.1
>>
--
Måns Rullgård
