RE: [EXT] Re: [net v3 PATCH 1/5] octeontx2-af: Adjust Tx credits when MCS external bypass is disabled

[Geethasowjanya Akula]

> -----Original Message-----
> From: Simon Horman <horms@xxxxxxxxxx>
> Sent: Sunday, December 3, 2023 10:11 PM
> To: Geethasowjanya Akula <gakula@xxxxxxxxxxx>
> Cc: netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; kuba@xxxxxxxxxx;
> davem@xxxxxxxxxxxxx; pabeni@xxxxxxxxxx; edumazet@xxxxxxxxxx; Sunil
> Kovvuri Goutham <sgoutham@xxxxxxxxxxx>; Linu Cherian
> <lcherian@xxxxxxxxxxx>; Jerin Jacob Kollanukkaran <jerinj@xxxxxxxxxxx>;
> Subbaraya Sundeep Bhatta <sbhatta@xxxxxxxxxxx>; Hariprasad Kelam
> <hkelam@xxxxxxxxxxx>
> Subject: [EXT] Re: [net v3 PATCH 1/5] octeontx2-af: Adjust Tx credits when
> MCS external bypass is disabled
> 
> External Email
> 
> ----------------------------------------------------------------------
> On Thu, Nov 30, 2023 at 01:28:14PM +0530, Geetha sowjanya wrote:
> > From: Nithin Dabilpuram <ndabilpuram@xxxxxxxxxxx>
> >
> > When MCS external bypass is disabled, MCS returns additional
> > 2 credits(32B) for every packet Tx'ed on LMAC. To account for these
> > extra credits, NIX_AF_TX_LINKX_NORM_CREDIT.CC_MCS_CNT
> > needs to be configured as otherwise NIX Tx credits would overflow and
> > will never be returned to idle state credit count causing issues with
> > credit control and MTU change.
> >
> > This patch fixes the same by configuring CC_MCS_CNT at probe time for
> > MCS enabled SoC's
> >
> > Fixes: bd69476e86fc ("octeontx2-af: cn10k: mcs: Install a default TCAM
> > for normal traffic")
> > Signed-off-by: Nithin Dabilpuram <ndabilpuram@xxxxxxxxxxx>
> > Signed-off-by: Geetha sowjanya <gakula@xxxxxxxxxxx>
> > Signed-off-by: Sunil Goutham <sgoutham@xxxxxxxxxxx>
> > Reviewed-by: Wojciech Drewek <wojciech.drewek@xxxxxxxxx>
> 
> Hi Geetha and Nithin,
> 
> some minor feedback from my side.
> 
> > ---
> >  drivers/net/ethernet/marvell/octeontx2/af/mcs.c     | 12 ++++++++++++
> >  drivers/net/ethernet/marvell/octeontx2/af/mcs.h     |  2 ++
> >  drivers/net/ethernet/marvell/octeontx2/af/rvu.h     |  1 +
> >  drivers/net/ethernet/marvell/octeontx2/af/rvu_nix.c |  8 ++++++++
> >  4 files changed, 23 insertions(+)
> >
> > diff --git a/drivers/net/ethernet/marvell/octeontx2/af/mcs.c
> > b/drivers/net/ethernet/marvell/octeontx2/af/mcs.c
> > index c43f19dfbd74..d6effbe46208 100644
> > --- a/drivers/net/ethernet/marvell/octeontx2/af/mcs.c
> > +++ b/drivers/net/ethernet/marvell/octeontx2/af/mcs.c
> > @@ -1219,6 +1219,17 @@ struct mcs *mcs_get_pdata(int mcs_id)
> >  	return NULL;
> >  }
> >
> > +bool is_mcs_bypass(int mcs_id)
> > +{
> > +	struct mcs *mcs_dev;
> > +
> > +	list_for_each_entry(mcs_dev, &mcs_list, mcs_list) {
> > +		if (mcs_dev->mcs_id == mcs_id)
> > +			return mcs_dev->bypass;
> > +	}
> > +	return true;
> > +}
> > +
> >  void mcs_set_port_cfg(struct mcs *mcs, struct mcs_port_cfg_set_req
> > *req)  {
> >  	u64 val = 0;
> > @@ -1447,6 +1458,7 @@ static void mcs_set_external_bypass(struct mcs
> *mcs, u8 bypass)
> >  	else
> >  		val &= ~BIT_ULL(6);
> >  	mcs_reg_write(mcs, MCSX_MIL_GLOBAL, val);
> > +	mcs->bypass = bypass;
> 
> I think that bool would be a more appropriate type than u8 for:
> 
> * The bypass parameter of mcs_set_external_bypass()
> * The bypass field of struct mcs
> 
> >  }
> >
> >  static void mcs_global_cfg(struct mcs *mcs) diff --git
> > a/drivers/net/ethernet/marvell/octeontx2/af/mcs.h
> > b/drivers/net/ethernet/marvell/octeontx2/af/mcs.h
> > index 0f89dcb76465..ccd43c3f3460 100644
> > --- a/drivers/net/ethernet/marvell/octeontx2/af/mcs.h
> > +++ b/drivers/net/ethernet/marvell/octeontx2/af/mcs.h
> > @@ -149,6 +149,7 @@ struct mcs {
> >  	u16			num_vec;
> >  	void			*rvu;
> >  	u16			*tx_sa_active;
> > +	u8                      bypass;
> >  };
> >
> >  struct mcs_ops {
> > @@ -206,6 +207,7 @@ void mcs_get_custom_tag_cfg(struct mcs *mcs,
> > struct mcs_custom_tag_cfg_get_req *  int mcs_alloc_ctrlpktrule(struct
> > rsrc_bmap *rsrc, u16 *pf_map, u16 offset, u16 pcifunc);  int
> > mcs_free_ctrlpktrule(struct mcs *mcs, struct
> > mcs_free_ctrl_pkt_rule_req *req);  int mcs_ctrlpktrule_write(struct
> > mcs *mcs, struct mcs_ctrl_pkt_rule_write_req *req);
> > +bool is_mcs_bypass(int mcs_id);
> >
> >  /* CN10K-B APIs */
> >  void cn10kb_mcs_set_hw_capabilities(struct mcs *mcs); diff --git
> > a/drivers/net/ethernet/marvell/octeontx2/af/rvu.h
> > b/drivers/net/ethernet/marvell/octeontx2/af/rvu.h
> > index c4d999ef5ab4..9887edccadf7 100644
> > --- a/drivers/net/ethernet/marvell/octeontx2/af/rvu.h
> > +++ b/drivers/net/ethernet/marvell/octeontx2/af/rvu.h
> > @@ -345,6 +345,7 @@ struct nix_hw {
> >  	struct nix_txvlan txvlan;
> >  	struct nix_ipolicer *ipolicer;
> >  	u64    *tx_credits;
> > +	u64 cc_mcs_cnt;
> >  };
> >
> >  /* RVU block's capabilities or functionality, diff --git
> > a/drivers/net/ethernet/marvell/octeontx2/af/rvu_nix.c
> > b/drivers/net/ethernet/marvell/octeontx2/af/rvu_nix.c
> > index c112c71ff576..daafce5fef46 100644
> > --- a/drivers/net/ethernet/marvell/octeontx2/af/rvu_nix.c
> > +++ b/drivers/net/ethernet/marvell/octeontx2/af/rvu_nix.c
> > @@ -12,6 +12,7 @@
> >  #include "rvu_reg.h"
> >  #include "rvu.h"
> >  #include "npc.h"
> > +#include "mcs.h"
> >  #include "cgx.h"
> >  #include "lmac_common.h"
> >  #include "rvu_npc_hash.h"
> > @@ -4389,6 +4390,12 @@ static void nix_link_config(struct rvu *rvu, int
> blkaddr,
> >  			    SDP_HW_MAX_FRS << 16 | NIC_HW_MIN_FRS);
> >  	}
> >
> > +	/* Get MCS external bypass status for CN10K-B */
> > +	if (mcs_get_blkcnt() == 1) {
> > +		/* Adjust for 2 credits when external bypass is disabled */
> > +		nix_hw->cc_mcs_cnt = is_mcs_bypass(0) ? 0 : 2;
> 
> Perhaps it doesn't matter, but to me it seems a bit excessive to use a 64-bit
> field to store such small values.
> 
> > +	}
> > +
> >  	/* Set credits for Tx links assuming max packet length allowed.
> >  	 * This will be reconfigured based on MTU set for PF/VF.
> >  	 */
> > @@ -4412,6 +4419,7 @@ static void nix_link_config(struct rvu *rvu, int
> blkaddr,
> >  			tx_credits = (lmac_fifo_len - lmac_max_frs) / 16;
> >  			/* Enable credits and set credit pkt count to max
> allowed */
> >  			cfg =  (tx_credits << 12) | (0x1FF << 2) | BIT_ULL(1);
> > +			cfg |= (nix_hw->cc_mcs_cnt << 32);
> 
> I do see that cc_mcs_cnt needs to be 64-bit here to avoid truncation.
> But overall I think this function could benefit from the use of FIELD_PREP(),
> which I think would side-step that problem.
Thanks for the feedback. Will submit next version with the suggested changes.
> 
> >
> >  			link = iter + slink;
> >  			nix_hw->tx_credits[link] = tx_credits;
> > --
> > 2.25.1
> >