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

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

Hi Nicolas,

On 11/3/22 15:59, Chautru, Nicolas wrote:
> Hi Maxime,
> 
>> -----Original Message-----
>> From: Maxime Coquelin <maxime.coquelin@redhat.com>
>> Sent: Thursday, November 3, 2022 7:10 AM
>> To: Vargas, Hernan <hernan.vargas@intel.com>; dev@dpdk.org;
>> gakhil@marvell.com; trix@redhat.com
>> Cc: Chautru, Nicolas <nicolas.chautru@intel.com>; Zhang, Qi Z
>> <qi.z.zhang@intel.com>
>> Subject: Re: [PATCH v7 1/1] baseband/acc100: add detection for deRM corner
>> cases
>>
>>
>>
>> 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?
> 
> As you can guess this notably allows customer do consider running deRM from here as a local patch hence keeping the q_data accessible.
> Basically we keep the prototype of the function enqueue_ldpc_dec_one_op_cb() compatible with such usage.
> I believe this is a good practice here. Let us know if you are not convinced.

I think it is better to just warn the user, without adding unused
parameters.

Thanks,
Maxime

> Thanks
> Nic
> 
>>
>>> +			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;
>