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qcacmn: DP Tx path change for H/W alignment requirement

Telusuri Sumber 
Transmit H/W requires that metadata sent as packet pre-header
should not be overlapping with the packet, as it might cause stalls
in the bus and might affect performance. For this reason, we are
removing align_pad bytes that we were adding by default for all
non-8-byte aligned frames and setting pkt_offset as 0 in Tx descriptor,
so that H/W does not read any metadata by default. H/W team confirmed that
8-byte alignment requirement is not there for frames which do not
have any metadata (Mesh/OCB/TDLS etc).

Change-Id: I2afdeaa49bc8306e7072cf5945762f19d6e4115f
CRs-Fixed: 2138287
This commit is contained in:
Pamidipati, Vijay
2017-11-05 16:18:25 +05:30
committed by snandini
orang tua 1493b989c7
melakukan 871850e015
1 mengubah file dengan 12 tambahan dan 20 penghapusan
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32
dp/wifi3.0/dp_tx.c
Melihat File

@@ -536,24 +536,7 @@ struct dp_tx_desc_s *dp_tx_prepare_desc_single(struct dp_vdev *vdev,
tx_desc->vdev = vdev;
tx_desc->pdev = pdev;
tx_desc->msdu_ext_desc = NULL;
/**
* For non-scatter regular frames, buffer pointer is directly
* programmed in TCL input descriptor instead of using an MSDU
* extension descriptor.For this cass, HW requirement is that
* descriptor should always point to a 8-byte aligned address.
*
* So we add alignment pad to start of buffer, and specify the actual
* start of data through pkt_offset
*/
align_pad = ((unsigned long) qdf_nbuf_data(nbuf)) & 0x7;
if (qdf_nbuf_push_head(nbuf, align_pad) == NULL) {
QDF_TRACE(QDF_MODULE_ID_DP, QDF_TRACE_LEVEL_ERROR,
"qdf_nbuf_push_head failed\n");
goto failure;
}
tx_desc->pkt_offset = align_pad;
tx_desc->pkt_offset = 0;
/*
* For special modes (vdev_type == ocb or mesh), data frames should be
@@ -562,8 +545,10 @@ struct dp_tx_desc_s *dp_tx_prepare_desc_single(struct dp_vdev *vdev,
* These are filled in HTT MSDU descriptor and sent in frame pre-header.
* These frames are sent as exception packets to firmware.
*
* HW requirement is that metadata should always point to a
* 8-byte aligned address. So we add alignment pad to start of buffer.
* HTT Metadata should be ensured to be multiple of 8-bytes,
* to get 8-byte aligned start address along with align_pad added above
* to get 8-byte aligned start address along with align_pad added
*
* |-----------------------------|
* | |
@@ -586,11 +571,18 @@ struct dp_tx_desc_s *dp_tx_prepare_desc_single(struct dp_vdev *vdev,
*/
if (qdf_unlikely(vdev->mesh_vdev ||
(vdev->opmode == wlan_op_mode_ocb))) {
align_pad = ((unsigned long) qdf_nbuf_data(nbuf)) & 0x7;
if (qdf_nbuf_push_head(nbuf, align_pad) == NULL) {
QDF_TRACE(QDF_MODULE_ID_DP, QDF_TRACE_LEVEL_ERROR,
"qdf_nbuf_push_head failed\n");
goto failure;
}
htt_hdr_size = dp_tx_prepare_htt_metadata(vdev, nbuf,
meta_data);
if (htt_hdr_size == 0)
goto failure;
tx_desc->pkt_offset += htt_hdr_size;
tx_desc->pkt_offset = align_pad + htt_hdr_size;
tx_desc->flags |= DP_TX_DESC_FLAG_TO_FW;
is_exception = 1;
}