wifi: iwlwifi: pcie: give up mem read if HW is dead

If the hardware is not responding, as indicated by (currently)
five consecutive HW errors during reading, then just give up
and fail, rather than attempting forever and forever for this
to not return any useful data anyway.

Even though we no longer completely deadlock the machine if it
takes a long time, we still make it pretty much unusable since
we'll eventually hold the RTNL while waiting for this process
to finish.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230913145231.345af79f431c.I5ecde6b76b1e3a1572bd59d3cf8f827e767cedeb@changeidSigned-off-by: Johannes Berg <johannes.berg@intel.com>

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

@@ -2288,6 +2288,8 @@ static void iwl_trans_pcie_release_nic_access(struct iwl_trans *trans)
 static int iwl_trans_pcie_read_mem(struct iwl_trans *trans, u32 addr,
 				   void *buf, int dwords)
 {
+#define IWL_MAX_HW_ERRS 5
+	unsigned int num_consec_hw_errors = 0;
 	int offs = 0;
 	u32 *vals = buf;
 
@@ -2303,6 +2305,17 @@ static int iwl_trans_pcie_read_mem(struct iwl_trans *trans, u32 addr,
 			while (offs < dwords) {
 				vals[offs] = iwl_read32(trans,
 							HBUS_TARG_MEM_RDAT);
+
+				if (iwl_trans_is_hw_error_value(vals[offs]))
+					num_consec_hw_errors++;
+				else
+					num_consec_hw_errors = 0;
+
+				if (num_consec_hw_errors >= IWL_MAX_HW_ERRS) {
+					iwl_trans_release_nic_access(trans);
+					return -EIO;
+				}
+
 				offs++;
 
 				if (time_after(jiffies, end)) {