netdev - RE: [PATCH net-next v2 6/8] ravb: Add net_features and net_hw_features to struct ravb_hw

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Message-ID: <OS0PR01MB5922967B28A3D4E8252F8A9C86F99@OS0PR01MB5922.jpnprd01.prod.outlook.com>
Date:   Thu, 12 Aug 2021 07:35:36 +0000
From:   Biju Das <biju.das.jz@...renesas.com>
To:     Sergei Shtylyov <sergei.shtylyov@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
CC:     Geert Uytterhoeven <geert+renesas@...der.be>,
        Sergey Shtylyov <s.shtylyov@...russia.ru>,
        Adam Ford <aford173@...il.com>, Andrew Lunn <andrew@...n.ch>,
        Yuusuke Ashizuka <ashiduka@...itsu.com>,
        Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-renesas-soc@...r.kernel.org" 
        <linux-renesas-soc@...r.kernel.org>,
        Chris Paterson <Chris.Paterson2@...esas.com>,
        Biju Das <biju.das@...renesas.com>,
        Prabhakar Mahadev Lad <prabhakar.mahadev-lad.rj@...renesas.com>
Subject: RE: [PATCH net-next v2 6/8] ravb: Add net_features and
 net_hw_features to struct ravb_hw_info

Hi Sergei,

Thanks for the feedback.

> Subject: Re: [PATCH net-next v2 6/8] ravb: Add net_features and
> net_hw_features to struct ravb_hw_info
> 
> Hello!
> 
> On 8/5/21 10:18 PM, Biju Das wrote:
> 
> [...]
> >>> On R-Car the checksum calculation on RX frames is done by the E-MAC
> >>> module, whereas on RZ/G2L it is done by the TOE.
> >>>
> >>> TOE calculates the checksum of received frames from E-MAC and
> >>> outputs it to DMAC. TOE also calculates the checksum of transmission
> >>> frames from DMAC and outputs it E-MAC.
> >>>
> >>> Add net_features and net_hw_features to struct ravb_hw_info, to
> >>> support subsequent SoCs without any code changes in the ravb_probe
> >> function.
> >>>
> >>> Signed-off-by: Biju Das <biju.das.jz@...renesas.com>
> >>> Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> >>
> >> [...]
> >>> diff --git a/drivers/net/ethernet/renesas/ravb.h
> >>> b/drivers/net/ethernet/renesas/ravb.h
> >>> index b765b2b7d9e9..3df813b2e253 100644
> >>> --- a/drivers/net/ethernet/renesas/ravb.h
> >>> +++ b/drivers/net/ethernet/renesas/ravb.h
> >>> @@ -991,6 +991,8 @@ enum ravb_chip_id {  struct ravb_hw_info {
> >>>  	const char (*gstrings_stats)[ETH_GSTRING_LEN];
> >>>  	size_t gstrings_size;
> >>> +	netdev_features_t net_hw_features;
> >>> +	netdev_features_t net_features;
> >>
> >>    Do we really need both of these here?
> >
> > R-Car has only Rx Checksum on E-Mac, where as Geth supports Rx Check Sum
> on E-Mac or Rx/Tx CheckSum on TOE.
> > So there is a hw difference. Please let me know what is the best way to
> handle this?
> 
>    I meant that we could go with only one field of the net_features...
> Alternatively, we could use our own feature bits...

Basically are you suggesting some thing like unsigned hwcsum_tx_rx: 1;

Then,

if (hwcsum_tx_rx) {
	ndev->hw_features = NETIF_F_HW_CSUM | NETIF_F_RXCSUM;
} else {
	ndev->features = NETIF_F_RXCSUM;
	ndev->hw_features = NETIF_F_RXCSUM;
}

Cheers,
Biju