linux-kernel - Re: [PATCH] net: ti: icssg-prueth: Fix tx_total

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Message-ID: <524856b3-6876-48d1-aebf-09f7f6c71f7b@lunn.ch>
Date:   Thu, 12 Oct 2023 17:28:27 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     MD Danish Anwar <danishanwar@...com>
Cc:     Paolo Abeni <pabeni@...hat.com>, Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org, srk@...com,
        Vignesh Raghavendra <vigneshr@...com>, r-gunasekaran@...com,
        Roger Quadros <rogerq@...nel.org>
Subject: Re: [PATCH] net: ti: icssg-prueth: Fix tx_total_bytes count

On Thu, Oct 12, 2023 at 10:51:12AM +0530, MD Danish Anwar wrote:
> Hi Andrew,
> 
> On 11/10/23 18:11, Andrew Lunn wrote:
> >> @@ -29,7 +30,12 @@ void emac_update_hardware_stats(struct prueth_emac *emac)
> >>  			     base + icssg_all_stats[i].offset,
> >>  			     val);
> >>  
> >> +		if (!strncmp(icssg_ethtool_stats[i].name, "tx_good_frames", ETH_GSTRING_LEN))
> >> +			tx_pkt_cnt = val;
> > 
> > Doing a strncmp seems very expensive. Could you make use of
> > icssg_stats.offset?
> > 
> 
> Sure. I can define the offset of these two stats and then use them in if
> condition as below.
> 
> #define ICSSG_TX_PACKET_OFFSET 0xA0
> #define ICSSG_TX_BYTE_OFFSET   0xEC
> 
> if (icssg_ethtool_stats[i].offset == ICSSG_TX_PACKET_OFFSET)
> 	tx_pkt_cnt = val;
> 
> if (icssg_ethtool_stats[i].offset == ICSSG_TX_BYTE_OFFSET)
> 	emac->stats[i] -= tx_pkt_cnt * 8;

That is much better. Also consider adding something like:

BUILD_BUG_ON(ICSSG_TX_PACKET_OFFSET < ICSSG_TX_BYTE_OFFSET)

I've no idea if this is correct. Just something to prove at build time
that ICSSG_TX_PACKET_OFFSET is read before ICSSG_TX_BYTE_OFFSET.

     Andrew