Changeset 327f4e1 in rtems-libbsd for linux/drivers

sdk_dpaa: What to do with tail queue drop?

The issue is this:

static int dpaa_eth_macless_probe(struct platform_device *_of_dev)
{
[...]

INIT_LIST_HEAD(&priv->dpa_fq_list);

err = dpa_fq_probe_macless(dev, &priv->dpa_fq_list, RX);
if (!err)

err = dpa_fq_probe_macless(dev, &priv->dpa_fq_list,

TX);

if (err < 0)

goto fq_probe_failed;

[...]

/* Add the FQs to the interface, and make them active */
/* For MAC-less devices we only get here for RX frame queues

• initialization, which are the TX queues of the other
• partition.
• It is safe to rely on one partition to set the FQ taildrop
• threshold for the TX queues of the other partition
• because the ERN notifications will be received by the
• partition doing qman_enqueue. */

err = dpa_fqs_init(dev, &priv->dpa_fq_list, true);
if (err < 0)

goto fq_alloc_failed;

[...]

The priv->dpa_fq_list contains a list of FQ_TYPE_RX_PCD and FQ_TYPE_TX
items. I don't understand what the "For MAC-less devices we only get
here for RX frame queues initialization" means in this context. The
td_enable == true in dpa_fqs_init(). So, we have:

int dpa_fq_init(struct dpa_fq *dpa_fq, bool td_enable)
{
[...]

if (dpa_fq->fq_type == FQ_TYPE_TX

dpa_fq->fq_type == FQ_TYPE_TX_CONFIRM

dpa_fq->fq_type == FQ_TYPE_TX_CONF_MQ) {

[...]

initfq.we_mask |= QM_INITFQ_WE_OAC;

[...]

}

if (td_enable) {

initfq.we_mask |= QM_INITFQ_WE_TDTHRESH;
qm_fqd_taildrop_set(&initfq.fqd.td,

DPA_FQ_TD, 1);

initfq.fqd.fq_ctrl = QM_FQCTRL_TDE;

}

The td_enable == true && dpa_fq->fq_type == FQ_TYPE_TX causes later:

int qman_init_fq(struct qman_fq *fq, u32 flags, struct qm_mcc_initfq *opts)
{
[...]

if (opts && (opts->we_mask & QM_INITFQ_WE_OAC)) {

/* And can't be set at the same time as TDTHRESH */
if (opts->we_mask & QM_INITFQ_WE_TDTHRESH)

return -EINVAL;

}

This aborts the initialization of the MAC-less driver. I don't
understand why this path doesn't happen on the SDK Linux system.

Update #3277.