On Thu, 2019-01-24 at 14:05 +0900, Atsushi Nemoto wrote:
> On Wed, 23 Jan 2019 14:47:06 -0800, Dalon L Westergreen <
> [email protected]> wrote:
> > > > if (inuse) { /* Tx FIFO is not empty */
> > > > - ready = priv->tx_prod - priv->tx_cons - inuse - 1;
> > > > + ready = priv->tx_prod - priv->tx_cons - inuse;
> > dont think my last email went through..
> >
> > I am not sure about this. This register indicates the number of entries
> > still to be processed by the dma. the -1 is intended to represent the
> > decriptor currently being processed. If ready is
> > priv->tx_prod - priv->tx_cons - inuse couldn't you end up processing 1
> > too many packets? IE: ready is 1 greater then the actual completed
> > packets?
> >
> > I do agree that we should not be returning a negative value, but i dont
> > think i agree removing the -1 is the answer. perhaps just check that ready
> > is greater than 0?
>
> Thank you for review.
>
> I agree with you. It would be OK returning a possibly off-by-one
> value unless it is not an negative value.
>
> Then, how about this instead?
>
This works for me. thanks.
> --- a/drivers/net/ethernet/altera/altera_msgdma.c
> +++ b/drivers/net/ethernet/altera/altera_msgdma.c
> @@ -145,7 +145,8 @@ u32 msgdma_tx_completions(struct altera_tse_private *priv)
> & 0xffff;
>
> if (inuse) { /* Tx FIFO is not empty */
> - ready = priv->tx_prod - priv->tx_cons - inuse - 1;
> + ready = max_t(int,
> + priv->tx_prod - priv->tx_cons - inuse - 1, 0);
> } else {
> /* Check for buffered last packet */
> status = csrrd32(priv->tx_dma_csr, msgdma_csroffs(status));
