iwlwifi: get the correct HCMD in the response handler

Until now, the response handler of a Host Command got the
exact same pointer that was also given to the DMA engine.
We almost never need to the Host Command that was sent while
handling its response, but when we do need it, we see that
the command has been modified.

This mystery has been elucidated. The FH (our DMA engine)
writes its meta data on the buffer in the DRAM. Of course it
copies the buffer to the NIC first. This was known to happen
for Tx command, but as a matter of fact, it happens to all
TFD brought by the FH which doesn't care much about what it
brings from DRAM to internal SRAM.

So copy the Host Command to yet another buffer so that we
can properly pass the buffer that was sent originally to the
fw. Do that only if it was request by the user since very
few flows need to get the HCMD sent in the response handler.

Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 21 insertions, 5 deletions

diff --git a/drivers/net/wireless/iwlwifi/pcie/tx.c b/drivers/net/wireless/iwlwifi/pcie/tx.c
index 6baf8deef519..392d2bc5e357 100644
--- a/drivers/net/wireless/iwlwifi/pcie/tx.c
+++ b/drivers/net/wireless/iwlwifi/pcie/tx.c
@@ -521,7 +521,7 @@ static int iwl_enqueue_hcmd(struct iwl_trans *trans, struct iwl_host_cmd *cmd)
 	u16 copy_size, cmd_size;
 	bool had_nocopy = false;
 	int i;
-	u8 *cmd_dest;
+	u32 cmd_pos;
 #ifdef CONFIG_IWLWIFI_DEVICE_TRACING
 	const void *trace_bufs[IWL_MAX_CMD_TFDS + 1] = {};
 	int trace_lens[IWL_MAX_CMD_TFDS + 1] = {};
@@ -584,15 +584,31 @@ static int iwl_enqueue_hcmd(struct iwl_trans *trans, struct iwl_host_cmd *cmd)
 					 INDEX_TO_SEQ(q->write_ptr));
 
 	/* and copy the data that needs to be copied */
-
-	cmd_dest = out_cmd->payload;
+	cmd_pos = offsetof(struct iwl_device_cmd, payload);
 	for (i = 0; i < IWL_MAX_CMD_TFDS; i++) {
 		if (!cmd->len[i])
 			continue;
 		if (cmd->dataflags[i] & IWL_HCMD_DFL_NOCOPY)
 			break;
-		memcpy(cmd_dest, cmd->data[i], cmd->len[i]);
-		cmd_dest += cmd->len[i];
+		memcpy((u8 *)out_cmd + cmd_pos, cmd->data[i], cmd->len[i]);
+		cmd_pos += cmd->len[i];
+	}
+
+	WARN_ON_ONCE(txq->entries[idx].copy_cmd);
+
+	/*
+	 * since out_cmd will be the source address of the FH, it will write
+	 * the retry count there. So when the user needs to receivce the HCMD
+	 * that corresponds to the response in the response handler, it needs
+	 * to set CMD_WANT_HCMD.
+	 */
+	if (cmd->flags & CMD_WANT_HCMD) {
+		txq->entries[idx].copy_cmd =
+			kmemdup(out_cmd, cmd_pos, GFP_ATOMIC);
+		if (unlikely(!txq->entries[idx].copy_cmd)) {
+			idx = -ENOMEM;
+			goto out;
+		}
 	}
 
 	IWL_DEBUG_HC(trans,