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

Simon Horman
2023-12-03T16:41:31Z

On Thu, Nov 30, 2023 at 01:28:14PM +0530, Geetha sowjanya wrote:
> From: Nithin Dabilpuram <ndabilpuram@marvell.com>
>
> 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@marvell.com>
> Signed-off-by: Geetha sowjanya <gakula@marvell.com>
> Signed-off-by: Sunil Goutham <sgoutham@marvell.com>
> Reviewed-by: Wojciech Drewek <wojciech.drewek@intel.com>

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.

>
> link = iter + slink;
> nix_hw->tx_credits[link] = tx_credits;
> --
> 2.25.1
>