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

[Sai Krishna Gajula]

> -----Original Message-----
> From: Simon Horman <simon.horman@xxxxxxxxxxxx>
> Sent: Wednesday, April 19, 2023 4:05 PM
> To: Sai Krishna Gajula <saikrishnag@xxxxxxxxxxx>
> Cc: davem@xxxxxxxxxxxxx; edumazet@xxxxxxxxxx; kuba@xxxxxxxxxx;
> pabeni@xxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; leon@xxxxxxxxxx; Sunil Kovvuri Goutham
> <sgoutham@xxxxxxxxxxx>; Geethasowjanya Akula <gakula@xxxxxxxxxxx>;
> Linu Cherian <lcherian@xxxxxxxxxxx>; Jerin Jacob Kollanukkaran
> <jerinj@xxxxxxxxxxx>; Hariprasad Kelam <hkelam@xxxxxxxxxxx>;
> Subbaraya Sundeep Bhatta <sbhatta@xxxxxxxxxxx>; Ratheesh Kannoth
> <rkannoth@xxxxxxxxxxx>
> 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@xxxxxxxxxxx>
> >
> > 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@xxxxxxxxxxx>
> > Signed-off-by: Sunil Kovvuri Goutham <sgoutham@xxxxxxxxxxx>
> > Signed-off-by: Sai Krishna <saikrishnag@xxxxxxxxxxx>
> 
> 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
> >