From 9018fd7f2a73e9b290f48a56b421558fa31e8b75 Mon Sep 17 00:00:00 2001
From: Bolarinwa Olayemi Saheed <refactormyself@gmail.com>
Date: Mon, 13 Jul 2020 19:55:27 +0200
Subject: [Backport 9018fd7f2a73] iwlegacy: Check the return value of
 pcie_capability_read_*()

On failure pcie_capability_read_dword() sets it's last parameter, val
to 0. However, with Patch 14/14, it is possible that val is set to ~0 on
failure. This would introduce a bug because (x & x) == (~0 & x).

This bug can be avoided without changing the function's behaviour if the
return value of pcie_capability_read_dword is checked to confirm success.

Check the return value of pcie_capability_read_dword() to ensure success.

Suggested-by: Bjorn Helgaas <bjorn@helgaas.com>
Signed-off-by: Bolarinwa Olayemi Saheed <refactormyself@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200713175529.29715-3-refactormyself@gmail.com
---
 src/common.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/common.c b/src/common.c
index 348c17ce72f5cd57b66fb5ae161b2381b3585bf3..f78e062df572abacb6ab7d3a271de85f5903247d 100644
--- a/src/common.c
+++ b/src/common.c
@@ -4286,8 +4286,8 @@ il_apm_init(struct il_priv *il)
 	 *    power savings, even without L1.
 	 */
 	if (il->cfg->set_l0s) {
-		pcie_capability_read_word(il->pci_dev, PCI_EXP_LNKCTL, &lctl);
-		if (lctl & PCI_EXP_LNKCTL_ASPM_L1) {
+		ret = pcie_capability_read_word(il->pci_dev, PCI_EXP_LNKCTL, &lctl);
+		if (!ret && (lctl & PCI_EXP_LNKCTL_ASPM_L1)) {
 			/* L1-ASPM enabled; disable(!) L0S  */
 			il_set_bit(il, CSR_GIO_REG,
 				   CSR_GIO_REG_VAL_L0S_ENABLED);
-- 
2.31.1