iwlwifi: pcie: fix DMA memory mapping / unmapping

22000 devices (previously referenced as A000) can support
short transmit queues. This means that we have less DMA
descriptors (TFD) for those shorter queues.
Previous devices must still have 256 TFDs for each queue
even if those 256 TFDs point to fewer buffers.

When I introduced support for the short queues for 22000
I broke older devices by assuming that they can also have
less TFDs in their queues. This led to several problems:

1) the payload of the commands weren't unmapped properly
   which caused the SWIOTLB to complain at some point.
2) the hardware could get confused and we get hardware
   crashes.

The corresponding bugzilla entries are:

https://bugzilla.kernel.org/show_bug.cgi?id=198201
https://bugzilla.kernel.org/show_bug.cgi?id=198265

Cc: stable@vger.kernel.org # 4.14+
Fixes: 4ecab5616023 ("iwlwifi: pcie: support short Tx queues for A000 device family")
Reviewed-by: Sharon, Sara <sara.sharon@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/intel/iwlwifi/pcie/internal.h

@@ -670,11 +670,15 @@ static inline u8 iwl_pcie_get_cmd_index(struct iwl_txq *q, u32 index)
 	return index & (q->n_window - 1);
 }
 
-static inline void *iwl_pcie_get_tfd(struct iwl_trans_pcie *trans_pcie,
+static inline void *iwl_pcie_get_tfd(struct iwl_trans *trans,
 				     struct iwl_txq *txq, int idx)
 {
-	return txq->tfds + trans_pcie->tfd_size * iwl_pcie_get_cmd_index(txq,
-									 idx);
+	struct iwl_trans_pcie *trans_pcie = IWL_TRANS_GET_PCIE_TRANS(trans);
+
+	if (trans->cfg->use_tfh)
+		idx = iwl_pcie_get_cmd_index(txq, idx);
+
+	return txq->tfds + trans_pcie->tfd_size * idx;
 }
 
 static inline void iwl_enable_rfkill_int(struct iwl_trans *trans)

drivers/net/wireless/intel/iwlwifi/pcie/tx-gen2.c

@@ -171,8 +171,6 @@ static void iwl_pcie_gen2_tfd_unmap(struct iwl_trans *trans,
 
 static void iwl_pcie_gen2_free_tfd(struct iwl_trans *trans, struct iwl_txq *txq)
 {
-	struct iwl_trans_pcie *trans_pcie = IWL_TRANS_GET_PCIE_TRANS(trans);
-
 	/* rd_ptr is bounded by TFD_QUEUE_SIZE_MAX and
 	 * idx is bounded by n_window
 	 */
@@ -181,7 +179,7 @@ static void iwl_pcie_gen2_free_tfd(struct iwl_trans *trans, struct iwl_txq *txq)
 	lockdep_assert_held(&txq->lock);
 
 	iwl_pcie_gen2_tfd_unmap(trans, &txq->entries[idx].meta,
-				iwl_pcie_get_tfd(trans_pcie, txq, idx));
+				iwl_pcie_get_tfd(trans, txq, idx));
 
 	/* free SKB */
 	if (txq->entries) {
@@ -364,11 +362,9 @@ struct iwl_tfh_tfd *iwl_pcie_gen2_build_tfd(struct iwl_trans *trans,
 					    struct sk_buff *skb,
 					    struct iwl_cmd_meta *out_meta)
 {
-	struct iwl_trans_pcie *trans_pcie = IWL_TRANS_GET_PCIE_TRANS(trans);
 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)skb->data;
 	int idx = iwl_pcie_get_cmd_index(txq, txq->write_ptr);
-	struct iwl_tfh_tfd *tfd =
-		iwl_pcie_get_tfd(trans_pcie, txq, idx);
+	struct iwl_tfh_tfd *tfd = iwl_pcie_get_tfd(trans, txq, idx);
 	dma_addr_t tb_phys;
 	bool amsdu;
 	int i, len, tb1_len, tb2_len, hdr_len;
@@ -565,8 +561,7 @@ static int iwl_pcie_gen2_enqueue_hcmd(struct iwl_trans *trans,
 	u8 group_id = iwl_cmd_groupid(cmd->id);
 	const u8 *cmddata[IWL_MAX_CMD_TBS_PER_TFD];
 	u16 cmdlen[IWL_MAX_CMD_TBS_PER_TFD];
-	struct iwl_tfh_tfd *tfd =
-		iwl_pcie_get_tfd(trans_pcie, txq, txq->write_ptr);
+	struct iwl_tfh_tfd *tfd = iwl_pcie_get_tfd(trans, txq, txq->write_ptr);
 
 	memset(tfd, 0, sizeof(*tfd));
 

drivers/net/wireless/intel/iwlwifi/pcie/tx.c

@@ -373,7 +373,7 @@ static void iwl_pcie_tfd_unmap(struct iwl_trans *trans,
 {
 	struct iwl_trans_pcie *trans_pcie = IWL_TRANS_GET_PCIE_TRANS(trans);
 	int i, num_tbs;
-	void *tfd = iwl_pcie_get_tfd(trans_pcie, txq, index);
+	void *tfd = iwl_pcie_get_tfd(trans, txq, index);
 
 	/* Sanity check on number of chunks */
 	num_tbs = iwl_pcie_tfd_get_num_tbs(trans, tfd);
@@ -2018,7 +2018,7 @@ static int iwl_fill_data_tbs(struct iwl_trans *trans, struct sk_buff *skb,
 	}
 
 	trace_iwlwifi_dev_tx(trans->dev, skb,
-			     iwl_pcie_get_tfd(trans_pcie, txq, txq->write_ptr),
+			     iwl_pcie_get_tfd(trans, txq, txq->write_ptr),
 			     trans_pcie->tfd_size,
 			     &dev_cmd->hdr, IWL_FIRST_TB_SIZE + tb1_len,
 			     hdr_len);
@@ -2092,7 +2092,7 @@ static int iwl_fill_data_tbs_amsdu(struct iwl_trans *trans, struct sk_buff *skb,
 		IEEE80211_CCMP_HDR_LEN : 0;
 
 	trace_iwlwifi_dev_tx(trans->dev, skb,
-			     iwl_pcie_get_tfd(trans_pcie, txq, txq->write_ptr),
+			     iwl_pcie_get_tfd(trans, txq, txq->write_ptr),
 			     trans_pcie->tfd_size,
 			     &dev_cmd->hdr, IWL_FIRST_TB_SIZE + tb1_len, 0);
 
@@ -2425,7 +2425,7 @@ int iwl_trans_pcie_tx(struct iwl_trans *trans, struct sk_buff *skb,
 	memcpy(&txq->first_tb_bufs[txq->write_ptr], &dev_cmd->hdr,
 	       IWL_FIRST_TB_SIZE);
 
-	tfd = iwl_pcie_get_tfd(trans_pcie, txq, txq->write_ptr);
+	tfd = iwl_pcie_get_tfd(trans, txq, txq->write_ptr);
 	/* Set up entry for this TFD in Tx byte-count array */
 	iwl_pcie_txq_update_byte_cnt_tbl(trans, txq, le16_to_cpu(tx_cmd->len),
 					 iwl_pcie_tfd_get_num_tbs(trans, tfd));