[PATCH 21.11] net/nfp: fix Tx descriptor free logic of NFD3

[Kevin Traynor]

On 08/11/2023 02:19, Chaoyong He wrote:
> [ upstream commit e97738919c2315e07c2e98b6a9cc3912c335364a ]
> 
> In the Tx descriptor free logic of nfd3, the former logic might force
> cast a negative number into a very big unsigned number, and which will
> cause potential problem in the xmit loop.
> 
> The xmit loop will continue in the place where it should break, and will
> overwrite the Tx descriptor which is not free to use by the PMD.
> 
> Fixes: 74a640dac864 ("net/nfp: avoid modulo operations for handling ring wrapping")
> 
> Signed-off-by: Chaoyong He<chaoyong.he at corigine.com>
> ---
>   drivers/net/nfp/nfp_rxtx.c | 8 ++++++--
>   1 file changed, 6 insertions(+), 2 deletions(-)

Applied to 21.11 branch. Thanks for backporting.