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Message-ID: <908c525b-10e2-464f-ad66-df431d48ca03@bp.renesas.com>
Date: Wed, 29 May 2024 20:07:03 +0100
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Subject: Re: [net-next PATCH v4 4/7] net: ravb: Refactor GbEth RX code path
To: Sergey Shtylyov <s.shtylyov@omp.ru>, "David S. Miller"
 <davem@davemloft.net>, Eric Dumazet <edumazet@google.com>,
 Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
 =?UTF-8?Q?Niklas_S=C3=B6derlund?= <niklas.soderlund+renesas@ragnatech.se>
Cc: Biju Das <biju.das.jz@bp.renesas.com>,
 Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>,
 Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>,
 netdev@vger.kernel.org, linux-renesas-soc@vger.kernel.org,
 linux-kernel@vger.kernel.org
References: <20240528150339.6791-1-paul.barker.ct@bp.renesas.com>
 <20240528150339.6791-5-paul.barker.ct@bp.renesas.com>
 <611a49b8-ecdb-6b91-9d3e-262bf3851f5b@omp.ru>
Content-Language: en-GB
From: Paul Barker <paul.barker.ct@bp.renesas.com>
Organization: Renesas Electronics Corporation
In-Reply-To: <611a49b8-ecdb-6b91-9d3e-262bf3851f5b@omp.ru>
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From: Paul Barker <paul.barker.ct@bp.renesas.com>
To: Sergey Shtylyov <s.shtylyov@omp.ru>, "David S. Miller"
 <davem@davemloft.net>, Eric Dumazet <edumazet@google.com>,
 Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
 =?UTF-8?Q?Niklas_S=C3=B6derlund?= <niklas.soderlund+renesas@ragnatech.se>
Cc: Biju Das <biju.das.jz@bp.renesas.com>,
 Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>,
 Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>,
 netdev@vger.kernel.org, linux-renesas-soc@vger.kernel.org,
 linux-kernel@vger.kernel.org
Message-ID: <908c525b-10e2-464f-ad66-df431d48ca03@bp.renesas.com>
Subject: Re: [net-next PATCH v4 4/7] net: ravb: Refactor GbEth RX code path
References: <20240528150339.6791-1-paul.barker.ct@bp.renesas.com>
 <20240528150339.6791-5-paul.barker.ct@bp.renesas.com>
 <611a49b8-ecdb-6b91-9d3e-262bf3851f5b@omp.ru>
In-Reply-To: <611a49b8-ecdb-6b91-9d3e-262bf3851f5b@omp.ru>

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On 29/05/2024 19:30, Sergey Shtylyov wrote:
> On 5/28/24 6:03 PM, Paul Barker wrote:
>=20
>> We can reduce code duplication in ravb_rx_gbeth().
>>
>> Signed-off-by: Paul Barker <paul.barker.ct@bp.renesas.com>
> [...]
>=20
>> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/et=
hernet/renesas/ravb_main.c
>> index 7df7d2e93a3a..c9c5cc641589 100644
>> --- a/drivers/net/ethernet/renesas/ravb_main.c
>> +++ b/drivers/net/ethernet/renesas/ravb_main.c
>> @@ -817,47 +817,54 @@ static int ravb_rx_gbeth(struct net_device *ndev=
, int budget, int q)
>>  				stats->rx_missed_errors++;
>>  		} else {
>>  			die_dt =3D desc->die_dt & 0xF0;
>> +			skb =3D ravb_get_skb_gbeth(ndev, entry, desc);
>>  			switch (die_dt) {
>=20
>    Why not do instead (as I've asked you alraedy):
>=20
> 			case DT_FSTART:
> 				priv->rx_1st_skb =3D skb;
> 				fallthrough;

I've avoided that change to keep patch 7/7 simpler (as we have to move
the assignment of skb later in that patch). I can change this if you
want though.

>=20
>>  			case DT_FSINGLE:
>> -				skb =3D ravb_get_skb_gbeth(ndev, entry, desc);
>=20
>=20
>> +			case DT_FSTART:
>> +				/* Start of packet:
>> +				 * Set initial data length.
>> +				 */
>=20
>    Please consider turning that block comment into one-liner...

Ack.

>=20
>>  				skb_put(skb, desc_len);
>> +
>> +				/* Save this SKB if the packet spans multiple
>> +				 * descriptors.
>> +				 */
>=20
>    This one too...
>    (The current line length limit is 100 columns.)

Ack. I'll re-flow some other lines with a 100 col limit as well - I'm
immediately thinking of the skb_copy_to_linear_data_offset call below.

>=20
>> +				if (die_dt =3D=3D DT_FSTART)
>> +					priv->rx_1st_skb =3D skb;
>=20
>    This needs to be done under *case* DT_FSTART above instead...

See above comment. We can do this under DT_FSTART in this patch if you
want, but this if condition will then come back in a revised patch 7/7.

>=20
>> +				break;
>> +
>> +			case DT_FMID:
>> +			case DT_FEND:
>> +				/* Continuing a packet:
>> +				 * Move data into the saved SKB.
>> +				 */
>> +				skb_copy_to_linear_data_offset(priv->rx_1st_skb,
>> +							       priv->rx_1st_skb->len,
>> +							       skb->data,
>> +							       desc_len);
>> +				skb_put(priv->rx_1st_skb, desc_len);
>> +				dev_kfree_skb(skb);
>> +
>> +				/* Set skb to point at the whole packet so that
>=20
>    Please call it consistently, either SKB or skb (I prefer this one).

Ack.

>=20
>> +				 * we only need one code path for finishing a
>> +				 * packet.
>> +				 */
>> +				skb =3D priv->rx_1st_skb;
>> +			}
>> +
>> +			switch (die_dt) {
>> +			case DT_FSINGLE:
>> +			case DT_FEND:
>> +				/* Finishing a packet:
>> +				 * Determine protocol & checksum, hand off to
>> +				 * NAPI and update our stats.
>> +				 */
>>  				skb->protocol =3D eth_type_trans(skb, ndev);
>>  				if (ndev->features & NETIF_F_RXCSUM)
>>  					ravb_rx_csum_gbeth(skb);
>> +				stats->rx_bytes +=3D skb->len;
>>  				napi_gro_receive(&priv->napi[q], skb);
>>  				rx_packets++;
>=20
>    Otherwise, this is very good patch! Sorry for letting in the duplcat=
e
> code earlier! :-)
>=20
> [...]
>=20
> MBR, Sergey

Thanks for the review!

--=20
Paul Barker
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