Hello!
On 02/13/2018 04:12 PM, Niklas Söderlund wrote:
>> On 02/12/2018 11:00 PM, Niklas Söderlund wrote:
>>
>>> Allow for chancing the MTU within the limit of the maximum size of a
>>
>> Changing. :-)
>
> Yes :-)
>
>>> descriptor (2048 bytes). Add the callback to change MTU from user-space
>>> and take the configurable MTU into account when configuring the
>>> hardware.
>>>
>>> Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@xxxxxxxxxxxx>
>> [...]
>>> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
>>> index c87f57ca44371586..a4870c9e42195802 100644
>>> --- a/drivers/net/ethernet/renesas/ravb_main.c
>>> +++ b/drivers/net/ethernet/renesas/ravb_main.c
>>> @@ -300,9 +300,9 @@ static void ravb_ring_format(struct net_device *ndev, int q)
>>> for (i = 0; i < priv->num_rx_ring[q]; i++) {
>>> /* RX descriptor */
>>> rx_desc = &priv->rx_ring[q][i];
>>> - rx_desc->ds_cc = cpu_to_le16(PKT_BUF_SZ);
>>> + rx_desc->ds_cc = cpu_to_le16(priv->rx_buf_sz);
>>> dma_addr = dma_map_single(ndev->dev.parent, priv->rx_skb[q][i]->data,
>>> - PKT_BUF_SZ,
>>> + le16_to_cpu(rx_desc->ds_cc),
>>
>> Why not 'priv->rx_buf_sz'?
>
> To align the arguments used with the one in ravb_rx() which uses
> le16_to_cpu(rx_desc->ds_cc) already before this patch.
Why?
> static bool ravb_rx(struct net_device *ndev, int *quota, int q)
> {
> ...
> /* Refill the RX ring buffers. */
> for (; priv->cur_rx[q] - priv->dirty_rx[q] > 0; priv->dirty_rx[q]++) {
> ...
> desc->ds_cc = cpu_to_le16(priv->rx_buf_sz);
>
> if (!priv->rx_skb[q][entry]) {
> ...
> dma_addr = dma_map_single(ndev->dev.parent, skb->data,
> le16_to_cpu(desc->ds_cc),
> DMA_FROM_DEVICE);
> ...
> }
> ...
> }
> ...
> }
>
> I have no preference one way or the other but I think both call sites
> should look the same :-)
Why? I don't like this idea at all...
>> [...]
>>> @@ -346,6 +346,10 @@ static int ravb_ring_init(struct net_device *ndev, int q)
>>> int ring_size;
>>> int i;
>>>
>>> + /* +16 gets room from the status from the card. */
>>> + priv->rx_buf_sz = (ndev->mtu <= 1492 ? PKT_BUF_SZ : ndev->mtu) +
>>> + ETH_HLEN + VLAN_HLEN + ETH_FCS_LEN + 16;
>>
>> Mhm, I don't think FCS gets added to the frame buffer...
It certainly isn't included, judging by the manuals... Instead 2-byte checksum is
included after the frame data (if checksumming is enabled).
> And why add 16?
>
> And +16 is added as the comment above states, to leave from the
> descriptor status appended by the hardware.
I don't see any appended status in the manuals, do you?
> This is already the case
> with PKT_BUF_SZ which for ravb is is set to 1538. MTU (1500) + ETH_HLEN
> (14) + VLAN_HLEN(4) + ETH_FCS_LEN(4) + ravb status (16) == 1538.
> This is also what the sh_eth driver do and I think it's value to keep
> these to driver as similar as possible in this regard, would you not
The DMA hardware is totally different, so I don't see any value in mirroring what sh_eth does...
> agree? If in deed the FSC is not added I think we should fix this for
> both drivers in a follow up commit.
Probably a good idea... :-)
[...]
MBR, Sergei
