netdev - Re: [PATCH] net: altera_tse: fix msgdma_tx_completion on non-zero fill

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Date:   Tue, 22 Jan 2019 11:20:57 -0600
From:   Thor Thayer <thor.thayer@...ux.intel.com>
To:     Atsushi Nemoto <atsushi.nemoto@...d.co.jp>, netdev@...r.kernel.org
Cc:     Tomonori Sakita <tomonori.sakita@...d.co.jp>,
        Dalon Westergreen <dalon.westergreen@...el.com>
Subject: Re: [PATCH] net: altera_tse: fix msgdma_tx_completion on non-zero
 fill_level case


On 1/21/19 2:29 AM, Atsushi Nemoto wrote:
> From: Tomonori Sakita <tomonori.sakita@...d.co.jp>
> 
> If fill_level was not zero and status was not BUSY,
> result of "tx_prod - tx_cons - inuse" might be zero.
> Subtracting 1 unconditionally results invalid negative return value
> on this case.
> The subtraction is not needed if fill_level was not zero.
> 
> Signed-off-by: Tomonori Sakita <tomonori.sakita@...d.co.jp>
> Signed-off-by: Atsushi Nemoto <atsushi.nemoto@...d.co.jp>
> ---
>   drivers/net/ethernet/altera/altera_msgdma.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/altera/altera_msgdma.c b/drivers/net/ethernet/altera/altera_msgdma.c
> index 0fb986b..3df73d3 100644
> --- a/drivers/net/ethernet/altera/altera_msgdma.c
> +++ b/drivers/net/ethernet/altera/altera_msgdma.c
> @@ -145,7 +145,7 @@ 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 = priv->tx_prod - priv->tx_cons - inuse;
>   	} else {
>   		/* Check for buffered last packet */
>   		status = csrrd32(priv->tx_dma_csr, msgdma_csroffs(status));
> 

I'm adding Dalon who has done a lot of work on msgdma. I'd like to get 
his comments.

Thanks,

Thor