[dpdk-dev] [PATCH v2] net/i40e: set no drop for traffic class

[Wu, Jingjing]

> -----Original Message-----
> From: Sexton, Rory
> Sent: Monday, January 16, 2017 11:52 PM
> To: Wu, Jingjing <jingjing.wu at intel.com>
> Cc: dev at dpdk.org; Sexton, Rory <rory.sexton at intel.com>; Marjanovic,
> Nemanja <nemanja.marjanovic at intel.com>
> Subject: [PATCH v2] net/i40e: set no drop for traffic class
> 
> From: Rory Sexton <rory.sexton at intel.com>
> 
> The default traffic class in i40e is set to drop versus on ixgbe it isset to no
> drop. This means when packets build up in the RX SRAM on the NIC, they are
> dropped, and they do this when the SW descriptor rings fill up.
> 
> This patch changes this behaviour and our testing shows there are no drops
> as a result.
> 
> Signed-off-by: Rory Sexton <rory.sexton at intel.com>
> Signed-off-by: Nemanja Marjanovic <nemanja.marjanovic at intel.com>
> ---
> v2:
> * Changed to use existing api to set priority register directly.
> 
>  drivers/net/i40e/i40e_ethdev.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/net/i40e/i40e_ethdev.c b/drivers/net/i40e/i40e_ethdev.c
> index 67778ba..97339b5 100644
> --- a/drivers/net/i40e/i40e_ethdev.c
> +++ b/drivers/net/i40e/i40e_ethdev.c
> @@ -2985,8 +2985,11 @@ static int
>  i40e_priority_flow_ctrl_set(__rte_unused struct rte_eth_dev *dev,
>  			    __rte_unused struct rte_eth_pfc_conf *pfc_conf)
> {
> +	struct i40e_hw *hw = I40E_DEV_PRIVATE_TO_HW(dev->data-
> >dev_private);
> +
>  	PMD_INIT_FUNC_TRACE();
> 
> +	I40E_WRITE_REG(hw, I40E_PRTDCB_TC2PFC, 0xff);

PRTDCB_TC2PFC  is the Bitmap who controls the use of Priority Flow Control (PFC) per each
TC. Bit n set to 1b indicates TC n uses PFC in Rx and Tx. The TC is referred as a no-drop TC.

And if look the rte_eth_pfc_conf, there is a field called priority, which would map to a TC.
Currently, the TC and priority is 1:1 map when dcb is enabled.
So how about change it like:
Check dcb info, and map the priority to tc, then
val = 0x1 << tc;
I40E_WRITE_REG(hw, I40E_PRTDCB_TC2PFC, val);

Thanks
Jingjing



>  	return -ENOSYS;
>  }
> 
> --
> 2.4.3