[PATCH wireless v3 2/4] wifi: iwlwifi: pcie: don't infer CSME presence from a failed read

[Navon John Lukose <navonjohnlukose@gmail.com>]

iwl_read_prph() returns 0x5a5a5a5a when it cannot grab NIC access, which
reads as "no CSME"; an all-ones CSR_HW_IF_CONFIG_REG reads as "CSME
present". me_present is never recomputed and gates the reset ladder, so one
bad read skews it for good. Reject both values. This does
downgrade a product reset that a poisoned read used to permit.

Cc: stable@vger.kernel.org
Fixes: 41fff83fe6cd ("wifi: iwlwifi: pcie: check for WiAMT/CSME presence")
Signed-off-by: Navon John Lukose <navonjohnlukose@gmail.com>
---
Applies as-is to 6.18.y and 7.2.y.

 .../net/wireless/intel/iwlwifi/pcie/gen1_2/trans.c  | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/gen1_2/trans.c b/drivers/net/wireless/intel/iwlwifi/pcie/gen1_2/trans.c
index a30854d..e5edcc2 100644
--- a/drivers/net/wireless/intel/iwlwifi/pcie/gen1_2/trans.c
+++ b/drivers/net/wireless/intel/iwlwifi/pcie/gen1_2/trans.c
@@ -4194,7 +4194,8 @@ static void iwl_pcie_recheck_me_status(struct work_struct *wk)
 	u32 val;
 
 	val = iwl_read32(trans_pcie->trans, CSR_HW_IF_CONFIG_REG);
-	trans_pcie->me_present = !!(val & CSR_HW_IF_CONFIG_REG_IAMT_UP);
+	if (!PCI_POSSIBLE_ERROR(val))
+		trans_pcie->me_present = !!(val & CSR_HW_IF_CONFIG_REG_IAMT_UP);
 }
 
 static void iwl_pcie_check_me_status(struct iwl_trans *trans)
@@ -4212,15 +4213,19 @@ static void iwl_pcie_check_me_status(struct iwl_trans *trans)
 		return;
 
 	val = iwl_read_prph(trans, CNVI_SCU_REG_FOR_ECO_1);
-	if (val & CNVI_SCU_REG_FOR_ECO_1_WIAMT_KNOWN) {
+	/* iwl_read_prph() returns 0x5a5a5a5a if it never reached the NIC, and
+	 * that value has WIAMT_KNOWN set and WIAMT_PRESENT clear
+	 */
+	if (!PCI_POSSIBLE_ERROR(val) && !iwl_trans_is_hw_error_value(val) &&
+	    (val & CNVI_SCU_REG_FOR_ECO_1_WIAMT_KNOWN)) {
 		trans_pcie->me_present =
 			!!(val & CNVI_SCU_REG_FOR_ECO_1_WIAMT_PRESENT);
 		return;
 	}
 
 	val = iwl_read32(trans, CSR_HW_IF_CONFIG_REG);
-	if (val & (CSR_HW_IF_CONFIG_REG_ME_OWN |
-		   CSR_HW_IF_CONFIG_REG_IAMT_UP)) {
+	if (!PCI_POSSIBLE_ERROR(val) && (val & (CSR_HW_IF_CONFIG_REG_ME_OWN |
+					       CSR_HW_IF_CONFIG_REG_IAMT_UP))) {
 		trans_pcie->me_present = 1;
 		return;
 	}