Subject: Re: [PATCH v2 net-next] net: stmmac: add drop transmit status feature

From: Andrew Lunn <[email-masked]>
Date: Wed, 12 Apr 2017 13:56:43 +0200

On Wed, Apr 12, 2017 at 10:26:20AM +0100, Joao Pinto wrote:
> When the Drop Transmit Status bit is set, the Tx packet status
> received from the MAC is dropped in the MTL. When this bit is reset,
> the Tx packet status received from the MAC is forwarded to the
> application. This feature will cause a performance improvement.
> 
> Signed-off-by: Joao Pinto <[email-masked]>
> ---
> changes v1->v2:
> - removed mask from dwmac4_enable_tx_drop()
> 
>  Documentation/devicetree/bindings/net/stmmac.txt      |  1 +
>  drivers/net/ethernet/stmicro/stmmac/common.h          |  2 ++
>  drivers/net/ethernet/stmicro/stmmac/dwmac4.h          |  1 +
>  drivers/net/ethernet/stmicro/stmmac/dwmac4_core.c     | 12 ++++++++++++
>  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c     |  3 +++
>  drivers/net/ethernet/stmicro/stmmac/stmmac_platform.c |  2 ++
>  include/linux/stmmac.h                                |  1 +
>  7 files changed, 22 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/net/stmmac.txt b/Documentation/devicetree/bindings/net/stmmac.txt
> index f652b0c..dbcb2cc 100644
> --- a/Documentation/devicetree/bindings/net/stmmac.txt
> +++ b/Documentation/devicetree/bindings/net/stmmac.txt
> @@ -60,6 +60,7 @@ Optional properties:
>  		 and MAC2MAC connection.
>  - snps,tso: this enables the TSO feature otherwise it will be managed by
>  		 MAC HW capability register. Only for GMAC4 and newer.
> +- snps,drop-tx-status: this enables drop tx status

Hi Joao

Was the conclusion from testing that this cannot be turned on by
default?

What sort of performance improvement did you get? Do you have some
benchmark numbers?

	  Andrew