netdev - Re: [RFC PATCH 1/2] net: macb: Add CAP to disable hardware TX checksum offloading

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Message-ID: <ad25fd2b-a3a0-28d5-4dd1-a7ccc935fff2@microchip.com>
Date:   Mon, 4 Jun 2018 17:13:28 +0200
From:   Nicolas Ferre <nicolas.ferre@...rochip.com>
To:     Jennifer Dahm <jennifer.dahm@...com>, <netdev@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>
CC:     Nathan Sullivan <nathan.sullivan@...com>
Subject: Re: [RFC PATCH 1/2] net: macb: Add CAP to disable hardware TX
 checksum offloading

On 25/05/2018 at 23:44, Jennifer Dahm wrote:
> Certain PHYs have significant bugs in their TX checksum offloading
> that cannot be solved in software. In order to accommodate these PHYS,
> add a CAP to disable this hardware.
> 
> Signed-off-by: Jennifer Dahm <jennifer.dahm@...com>
> ---
>   drivers/net/ethernet/cadence/macb.h      | 1 +
>   drivers/net/ethernet/cadence/macb_main.c | 8 ++++++--
>   2 files changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/cadence/macb.h b/drivers/net/ethernet/cadence/macb.h
> index 8665982..6b85e97 100644
> --- a/drivers/net/ethernet/cadence/macb.h
> +++ b/drivers/net/ethernet/cadence/macb.h
> @@ -635,6 +635,7 @@
>   #define MACB_CAPS_USRIO_DISABLED		0x00000010
>   #define MACB_CAPS_JUMBO				0x00000020
>   #define MACB_CAPS_GEM_HAS_PTP			0x00000040
> +#define MACB_CAPS_DISABLE_TX_HW_CSUM		0x00000080

Nitpicking: "DISABLED" tends to be at the end of the name...

>   #define MACB_CAPS_FIFO_MODE			0x10000000
>   #define MACB_CAPS_GIGABIT_MODE_AVAILABLE	0x20000000
>   #define MACB_CAPS_SG_DISABLED			0x40000000
> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
> index 3e93df5..a5d564b 100644
> --- a/drivers/net/ethernet/cadence/macb_main.c
> +++ b/drivers/net/ethernet/cadence/macb_main.c
> @@ -3360,8 +3360,12 @@ static int macb_init(struct platform_device *pdev)
>   		dev->hw_features |= MACB_NETIF_LSO;
>   
>   	/* Checksum offload is only available on gem with packet buffer */
> -	if (macb_is_gem(bp) && !(bp->caps & MACB_CAPS_FIFO_MODE))
> -		dev->hw_features |= NETIF_F_HW_CSUM | NETIF_F_RXCSUM;
> +	if (macb_is_gem(bp) && !(bp->caps & MACB_CAPS_FIFO_MODE)) {
> +		if (!(bp->caps & MACB_CAPS_DISABLE_TX_HW_CSUM))

Why not the other way around? negating a "disabled" feature is always 
challenge ;-)

> +			dev->hw_features |= NETIF_F_HW_CSUM | NETIF_F_RXCSUM;
> +		else
> +			dev->hw_features |= NETIF_F_RXCSUM;
> +	}
>   	if (bp->caps & MACB_CAPS_SG_DISABLED)
>   		dev->hw_features &= ~NETIF_F_SG;
>   	dev->features = dev->hw_features;
> 


-- 
Nicolas Ferre