netdev - Re: [net-next 05/11] i40e: fix for queue timing delays

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Message-Id: <20170325.200045.766752589165691684.davem@davemloft.net>
Date:   Sat, 25 Mar 2017 20:00:45 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     jeffrey.t.kirsher@...el.com
Cc:     carolyn.wyborny@...el.com, netdev@...r.kernel.org,
        nhorman@...hat.com, sassmann@...hat.com, jogreene@...hat.com
Subject: Re: [net-next 05/11] i40e: fix for queue timing delays

From: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Date: Sat, 25 Mar 2017 01:12:59 -0700

> From: Carolyn Wyborny <carolyn.wyborny@...el.com>
> 
> This patch adds a delay to Rx queue disables to accommodate HW needs.
> 
> Change-ID: I2864ca667ce5dcc2cc44f8718113b719742a46a1
> Signed-off-by: Carolyn Wyborny <carolyn.wyborny@...el.com>
> Tested-by: Andrew Bowers <andrewx.bowers@...el.com>
> Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
> ---
>  drivers/net/ethernet/intel/i40e/i40e_main.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c b/drivers/net/ethernet/intel/i40e/i40e_main.c
> index 5da990909a88..1435033faefe 100644
> --- a/drivers/net/ethernet/intel/i40e/i40e_main.c
> +++ b/drivers/net/ethernet/intel/i40e/i40e_main.c
> @@ -4181,6 +4181,8 @@ static int i40e_vsi_control_rx(struct i40e_vsi *vsi, bool enable)
>  		}
>  	}
>  
> +	/* HW needs up to 50ms to finish RX queue disable*/
> +	mdelay(50);

You just polled a register which indicates that the request is finished.
Needing futher time for the operation to complete doesn't make any
sense.

If this is really needed, you need to explain in the commit message, in
detail, what is really the problem here.

THanks.