linux-kernel - Re: [net PATCH v3 02/10] octeontx2-af: Fix start and end bit for scan config

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Message-ID: <BY3PR18MB470755330B9DF76944DD1493A0639@BY3PR18MB4707.namprd18.prod.outlook.com>
Date:   Thu, 20 Apr 2023 07:32:36 +0000
From:   Sai Krishna Gajula <saikrishnag@...vell.com>
To:     Simon Horman <simon.horman@...igine.com>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "leon@...nel.org" <leon@...nel.org>,
        Sunil Kovvuri Goutham <sgoutham@...vell.com>,
        Geethasowjanya Akula <gakula@...vell.com>,
        Linu Cherian <lcherian@...vell.com>,
        Jerin Jacob Kollanukkaran <jerinj@...vell.com>,
        Hariprasad Kelam <hkelam@...vell.com>,
        Subbaraya Sundeep Bhatta <sbhatta@...vell.com>,
        Ratheesh Kannoth <rkannoth@...vell.com>
Subject: Re: [net PATCH v3 02/10] octeontx2-af: Fix start and end bit for scan
 config


> -----Original Message-----
> From: Simon Horman <simon.horman@...igine.com>
> Sent: Wednesday, April 19, 2023 4:05 PM
> To: Sai Krishna Gajula <saikrishnag@...vell.com>
> Cc: davem@...emloft.net; edumazet@...gle.com; kuba@...nel.org;
> pabeni@...hat.com; netdev@...r.kernel.org; linux-
> kernel@...r.kernel.org; leon@...nel.org; Sunil Kovvuri Goutham
> <sgoutham@...vell.com>; Geethasowjanya Akula <gakula@...vell.com>;
> Linu Cherian <lcherian@...vell.com>; Jerin Jacob Kollanukkaran
> <jerinj@...vell.com>; Hariprasad Kelam <hkelam@...vell.com>;
> Subbaraya Sundeep Bhatta <sbhatta@...vell.com>; Ratheesh Kannoth
> <rkannoth@...vell.com>
> Subject: Re: [net PATCH v3 02/10] octeontx2-af: Fix start and end bit for
> scan config
> 
> On Wed, Apr 19, 2023 at 11:50:10AM +0530, Sai Krishna wrote:
> > From: Ratheesh Kannoth <rkannoth@...vell.com>
> >
> > Fix the NPC nibble start and end positions in the bit map.
> > for_each_set_bit_from() needs start bit as one bit prior and end bit
> > as one bit post position in the bit map
> >
> > Fixes: b747923afff8 ("octeontx2-af: Exact match support")
> > Signed-off-by: Ratheesh Kannoth <rkannoth@...vell.com>
> > Signed-off-by: Sunil Kovvuri Goutham <sgoutham@...vell.com>
> > Signed-off-by: Sai Krishna <saikrishnag@...vell.com>
> 
> I think it would be nice to explain why, and what effect this has.
> 
> Also, TBH, I'm unsure why the start needs to be one bit prior.
> 
Will expand the commit message with explanation of why, what effect of fix in v4 patch.

> > ---
> >  drivers/net/ethernet/marvell/octeontx2/af/rvu_npc_fs.c | 5 ++---
> >  1 file changed, 2 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/marvell/octeontx2/af/rvu_npc_fs.c
> > b/drivers/net/ethernet/marvell/octeontx2/af/rvu_npc_fs.c
> > index 006beb5cf98d..27603078689a 100644
> > --- a/drivers/net/ethernet/marvell/octeontx2/af/rvu_npc_fs.c
> > +++ b/drivers/net/ethernet/marvell/octeontx2/af/rvu_npc_fs.c
> > @@ -593,9 +593,8 @@ static int npc_scan_kex(struct rvu *rvu, int blkaddr,
> u8 intf)
> >  	 * exact match code.
> >  	 */
> >  	masked_cfg = cfg & NPC_EXACT_NIBBLE;
> > -	bitnr = NPC_EXACT_NIBBLE_START;
> > -	for_each_set_bit_from(bitnr, (unsigned long *)&masked_cfg,
> > -			      NPC_EXACT_NIBBLE_START) {
> > +	bitnr = NPC_EXACT_NIBBLE_START - 1;
> > +	for_each_set_bit_from(bitnr, (unsigned long *)&masked_cfg,
> > +NPC_EXACT_NIBBLE_END + 1) {
> >  		npc_scan_exact_result(mcam, bitnr, key_nibble, intf);
> >  		key_nibble++;
> >  	}
> > --
> > 2.25.1
> >