Re: [PATCH v7 1/1] baseband/acc100: add detection for deRM corner cases

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 11/1/22 05:13, Hernan Vargas wrote:
> Add function to detect if de-ratematch pre-processing is recommended for
> SW corner cases.
> Some specific 5GUL FEC corner cases may cause unintended back pressure
> and in some cases a potential stability issue on the ACC100.
> The PMD can detect such code block configuration and issue an info
> message to the user.
> 
> Signed-off-by: Hernan Vargas <hernan.vargas@intel.com>
> ---
>   drivers/baseband/acc/acc_common.h     |  8 ++++
>   drivers/baseband/acc/rte_acc100_pmd.c | 55 +++++++++++++++++++++++++--
>   2 files changed, 60 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/baseband/acc/acc_common.h b/drivers/baseband/acc/acc_common.h
> index eae7eab4e9..6213b0b61e 100644
> --- a/drivers/baseband/acc/acc_common.h
> +++ b/drivers/baseband/acc/acc_common.h
> @@ -123,6 +123,14 @@
>   #define ACC_HARQ_ALIGN_64B          64
>   #define ACC_MAX_ZC                  384
>   
> +/* De-ratematch code rate limitation for recommended operation */
> +#define ACC_LIM_03 2  /* 0.03 */
> +#define ACC_LIM_09 6  /* 0.09 */
> +#define ACC_LIM_14 9  /* 0.14 */
> +#define ACC_LIM_21 14 /* 0.21 */
> +#define ACC_LIM_31 20 /* 0.31 */
> +#define ACC_MAX_E (128 * 1024 - 2)
> +
>   /* Helper macro for logging */
>   #define rte_acc_log(level, fmt, ...) \
>   	rte_log(RTE_LOG_ ## level, RTE_LOG_NOTICE, fmt "\n", \
> diff --git a/drivers/baseband/acc/rte_acc100_pmd.c b/drivers/baseband/acc/rte_acc100_pmd.c
> index 23bc5d25bb..47609f95b7 100644
> --- a/drivers/baseband/acc/rte_acc100_pmd.c
> +++ b/drivers/baseband/acc/rte_acc100_pmd.c
> @@ -756,6 +756,14 @@ acc100_queue_setup(struct rte_bbdev *dev, uint16_t queue_id,
>   		ret = -ENOMEM;
>   		goto free_lb_out;
>   	}
> +	q->derm_buffer = rte_zmalloc_socket(dev->device->driver->name,
> +			RTE_BBDEV_TURBO_MAX_CB_SIZE * 10,
> +			RTE_CACHE_LINE_SIZE, conf->socket);
> +	if (q->derm_buffer == NULL) {
> +		rte_bbdev_log(ERR, "Failed to allocate derm_buffer memory");
> +		ret = -ENOMEM;
> +		goto free_companion_ring_addr;
> +	}
>   
>   	/*
>   	 * Software queue ring wraps synchronously with the HW when it reaches
> @@ -776,7 +784,7 @@ acc100_queue_setup(struct rte_bbdev *dev, uint16_t queue_id,
>   	q_idx = acc100_find_free_queue_idx(dev, conf);
>   	if (q_idx == -1) {
>   		ret = -EINVAL;
> -		goto free_companion_ring_addr;
> +		goto free_derm_buffer;
>   	}
>   
>   	q->qgrp_id = (q_idx >> ACC100_GRP_ID_SHIFT) & 0xF;
> @@ -804,6 +812,9 @@ acc100_queue_setup(struct rte_bbdev *dev, uint16_t queue_id,
>   	dev->data->queues[queue_id].queue_private = q;
>   	return 0;
>   
> +free_derm_buffer:
> +	rte_free(q->derm_buffer);
> +	q->derm_buffer = NULL;
>   free_companion_ring_addr:
>   	rte_free(q->companion_ring_addr);
>   	q->companion_ring_addr = NULL;
> @@ -890,6 +901,7 @@ acc100_queue_release(struct rte_bbdev *dev, uint16_t q_id)
>   		/* Mark the Queue as un-assigned */
>   		d->q_assigned_bit_map[q->qgrp_id] &= (0xFFFFFFFFFFFFFFFF -
>   				(uint64_t) (1 << q->aq_id));
> +		rte_free(q->derm_buffer);
>   		rte_free(q->companion_ring_addr);
>   		rte_free(q->lb_in);
>   		rte_free(q->lb_out);
> @@ -3111,10 +3123,41 @@ harq_loopback(struct acc_queue *q, struct rte_bbdev_dec_op *op,
>   	return 1;
>   }
>   
> +/* Assess whether a work around is recommended for the deRM corner cases */
> +static inline bool
> +derm_workaround_recommended(struct rte_bbdev_op_ldpc_dec *ldpc_dec, struct acc_queue *q)
> +{
> +	if (!is_acc100(q))
> +		return false;
> +	int32_t e = ldpc_dec->cb_params.e;
> +	int q_m = ldpc_dec->q_m;
> +	int z_c = ldpc_dec->z_c;
> +	int K = (ldpc_dec->basegraph == 1 ? ACC_K_ZC_1 : ACC_K_ZC_2) * z_c;
> +	bool recommended = false;
> +
> +	if (ldpc_dec->basegraph == 1) {
> +		if ((q_m == 4) && (z_c >= 320) && (e * ACC_LIM_31 > K * 64))
> +			recommended = true;
> +		else if ((e * ACC_LIM_21 > K * 64))
> +			recommended = true;
> +	} else {
> +		if (q_m <= 2) {
> +			if ((z_c >= 208) && (e * ACC_LIM_09 > K * 64))
> +				recommended = true;
> +			else if ((z_c < 208) && (e * ACC_LIM_03 > K * 64))
> +				recommended = true;
> +		} else if (e * ACC_LIM_14 > K * 64)
> +			recommended = true;
> +	}
> +
> +	return recommended;
> +}
> +
>   /** Enqueue one decode operations for ACC100 device in CB mode */
>   static inline int
>   enqueue_ldpc_dec_one_op_cb(struct acc_queue *q, struct rte_bbdev_dec_op *op,
> -		uint16_t total_enqueued_cbs, bool same_op)
> +		uint16_t total_enqueued_cbs, bool same_op,
> +		struct rte_bbdev_queue_data *q_data)
>   {
>   	int ret;
>   	if (unlikely(check_bit(op->ldpc_dec.op_flags,
> @@ -3168,6 +3211,12 @@ enqueue_ldpc_dec_one_op_cb(struct acc_queue *q, struct rte_bbdev_dec_op *op,
>   	} else {
>   		struct acc_fcw_ld *fcw;
>   		uint32_t seg_total_left;
> +
> +		if (derm_workaround_recommended(&op->ldpc_dec, q)) {
> +			RTE_SET_USED(q_data);
Why do we need q_data if it is not being used?

> +			rte_bbdev_log(INFO, "Corner case may require deRM pre-processing");
> +		}
> +
>   		fcw = &desc->req.fcw_ld;
>   		q->d->fcw_ld_fill(op, fcw, harq_layout);
>   
> @@ -3721,7 +3770,7 @@ acc100_enqueue_ldpc_dec_cb(struct rte_bbdev_queue_data *q_data,
>   			ops[i]->ldpc_dec.n_cb, ops[i]->ldpc_dec.q_m,
>   			ops[i]->ldpc_dec.n_filler, ops[i]->ldpc_dec.cb_params.e,
>   			same_op);
> -		ret = enqueue_ldpc_dec_one_op_cb(q, ops[i], i, same_op);
> +		ret = enqueue_ldpc_dec_one_op_cb(q, ops[i], i, same_op, q_data);
>   		if (ret < 0) {
>   			acc_enqueue_invalid(q_data);
>   			break;