Re: [PATCH net-next v6 06/15] bnxt_en: Allocate and free MPC channels from firmware

Responding to 2 High Sashiko comments:
https://sashiko.dev/#/patchset/20260810051358.1244418-1-michael.chan%40broadcom.com

On Sun, Aug 9, 2026 at 10:14 PM Michael Chan <[email protected]> wrote:
> +void bnxt_init_mpc_rings(struct bnxt *bp)
> +{
> +       struct bnxt_mpc_info *mpc = bp->mpc_info;
> +       int i, j;
> +
> +       if (!mpc)
> +               return;
> +
> +       for (i = 0; i < BNXT_MPC_TYPE_MAX; i++) {
> +               int num = mpc->mpc_ring_count[i];
> +
> +               for (j = 0; j < num; j++) {
> +                       struct bnxt_tx_ring_info *txr = &mpc->mpc_rings[i][j];
> +                       struct bnxt_ring_struct *ring = &txr->tx_ring_struct;
> +
> +                       txr->tx_prod = 0;
> +                       txr->tx_cons = 0;
> +                       txr->tx_hw_cons = 0;
> +                       WRITE_ONCE(txr->dev_state, 0);
> +                       ring->fw_ring_id = INVALID_HW_RING_ID;
> +               }
> +       }
> +}
> +

Sashiko:
When an MPC ring processes a transmission, will the generated completion in
__bnxt_poll_work() route to the wrong ring? ...

Response:
No, MPC transmissions generate new completion types
(CMP_TYPE_MPC_CMP_SHORT and CMP_TYPE_MPC_CMP_LONG), not the existing
TX completions.

> +static int bnxt_hwrm_one_mpc_ring_alloc(struct bnxt *bp,
> +                                       struct bnxt_tx_ring_info *txr)
> +{
> +       struct bnxt_cp_ring_info *cpr = txr->tx_cpr;
> +       struct bnxt_ring_struct *ring;
> +       int rc;
> +
> +       ring = &cpr->cp_ring_struct;

Sashiko:
Will txr->tx_cpr be NULL here during driver initialization?
During driver load, bnxt_alloc_mem() allocates MPC rings via
bnxt_alloc_mpcs(), which leaves txr->bnapi as NULL.
Immediately after, bnxt_alloc_all_cp_arrays() calls bnxt_set_mpc_cp_ring(),
which expects txr->bnapi to be initialized to match and set txr->tx_cpr.
Because txr->bnapi is still NULL, the match fails and txr->tx_cpr remains
NULL. ...

Response:
No, bnxt_alloc_all_cp_arrays() does not call bnxt_set_mpc_cp_ring().
It is called by bnxt_alloc_cp_rings() much later.  By then txr->napi
is already initialized and txr->tx_cpr will be set correctly.  So
txr->tx_cpr will not be NULL when we get here.