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From:   gregory.greenman@intel.com
To:     johannes@sipsolutions.net
Cc:     linux-wireless@vger.kernel.org,
        Johannes Berg <johannes.berg@intel.com>,
        Gregory Greenman <gregory.greenman@intel.com>
Subject: [PATCH 02/15] wifi: iwlwifi: pcie: give up mem read if HW is dead
Date:   Wed, 13 Sep 2023 14:56:38 +0300
Message-Id: <20230913145231.345af79f431c.I5ecde6b76b1e3a1572bd59d3cf8f827e767cedeb@changeid>
In-Reply-To: <20230913115651.190558-1-gregory.greenman@intel.com>
References: <20230913115651.190558-1-gregory.greenman@intel.com>
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From: Johannes Berg <johannes.berg@intel.com>

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>
---
 drivers/net/wireless/intel/iwlwifi/pcie/trans.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/trans.c b/drivers/net/wireless/intel/iwlwifi/pcie/trans.c
index 51012435e39b..93e10d7d12fb 100644
--- a/drivers/net/wireless/intel/iwlwifi/pcie/trans.c
+++ b/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)) {
-- 
2.38.1