Re: [PATCH net] net: stmmac: fix completely hung TX when using TSO

[Alexandre Torgue]

Hi Guys,

On 06/06/2017 10:00 AM, Giuseppe CAVALLARO wrote:
> Hi Niklas
>
> I get the point and I acked the patch but Alex, please, can you confirm
> that this issue has never seen on your boxes where the TSO has been
> fully tested? The initial development (commit f748be531) introduces
> the following:
>     (last_segment) && (buff_size < TSO_MAX_BUFF_SIZE),

I don't remember to have seen this kind of issue in the past but for 
sure I agree with this patch.

Acked-by: Alexandre TORGUE <alexandre.torgue@xxxxxx>

> ...
>
> On 6/6/2017 9:25 AM, Niklas Cassel wrote:
> > stmmac_tso_allocator can fail to set the Last Descriptor bit
> > on a descriptor that actually was the last descriptor.
> >
> > This happens when the buffer of the last descriptor ends
> > up having a size of exactly TSO_MAX_BUFF_SIZE.
> >
> > When the IP eventually reaches the next last descriptor,
> > which actually has the bit set, the DMA will hang.
> >
> > When the DMA hangs, we get a tx timeout, however,
> > since stmmac does not do a complete reset of the IP
> > in stmmac_tx_timeout, we end up in a state with
> > completely hung TX.
> >
> > Signed-off-by: Niklas Cassel <niklas.cassel@xxxxxxxx>
>
> Acked-by: Giuseppe Cavallaro <peppe.cavallaro@xxxxxx>
>
> > ---
> >   drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > index 68a188e74c54..440bea049a7f 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > @@ -2723,7 +2723,7 @@ static void stmmac_tso_allocator(struct
> > stmmac_priv *priv, unsigned int des,
> >             priv->hw->desc->prepare_tso_tx_desc(desc, 0, buff_size,
> >               0, 1,
> > -            (last_segment) && (buff_size < TSO_MAX_BUFF_SIZE),
> > +            (last_segment) && (tmp_len <= TSO_MAX_BUFF_SIZE),
> >               0, 0);
> >             tmp_len -= TSO_MAX_BUFF_SIZE;
>
> Regards
> Peppe