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, 13 insertions, 3 deletions

diff --git a/drivers/net/wireless/iwlwifi/pcie/rx.c b/drivers/net/wireless/iwlwifi/pcie/rx.c
index 39a6ca1f009..d80604a2bb1 100644
--- a/drivers/net/wireless/iwlwifi/pcie/rx.c
+++ b/drivers/net/wireless/iwlwifi/pcie/rx.c
@@ -421,13 +421,23 @@ static void iwl_rx_handle_rxbuf(struct iwl_trans *trans,
 		index = SEQ_TO_INDEX(sequence);
 		cmd_index = get_cmd_index(&txq->q, index);
 
-		if (reclaim)
-			cmd = txq->entries[cmd_index].cmd;
-		else
+		if (reclaim) {
+			struct iwl_pcie_tx_queue_entry *ent;
+			ent = &txq->entries[cmd_index];
+			cmd = ent->copy_cmd;
+			WARN_ON_ONCE(!cmd && ent->meta.flags & CMD_WANT_HCMD);
+		} else {
 			cmd = NULL;
+		}
 
 		err = iwl_op_mode_rx(trans->op_mode, &rxcb, cmd);
 
+		if (reclaim) {
+			/* The original command isn't needed any more */
+			kfree(txq->entries[cmd_index].copy_cmd);
+			txq->entries[cmd_index].copy_cmd = NULL;
+		}
+
 		/*
 		 * After here, we should always check rxcb._page_stolen,
 		 * if it is true then one of the handlers took the page.