On Wed, 23 Jan 2019 14:47:06 -0800, Dalon L Westergreen
<dalon.westergr...@linux.intel.com> 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?
--- 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));
--
If it was OK, I will post an updated patch.
---
Atsushi Nemoto
