[PATCH] wifi: iwlwifi: pcie: ensure RX_QUEUE_CB_SIZE fits bitfield for gcc-8|9

[Anders Roxell]

GCC-8 and GCC-9 emits a hard error when the value passed to
`u32_encode_bits()`. These versions somehow think that
RX_QUEUE_CB_SIZE(iwl_trans_get_num_rbds(trans)) is an out of bounds
constant.  Open code this calculation using FIELD_PREP() to avoid this
compile error.

error: call to '__field_overflow' declared with attribute error: value
doesn't fit into mask

Fixes: b8eee90f0ba5 ("wifi: iwlwifi: cfg: unify num_rbds config")
Reported-by: Linux Kernel Functional Testing <lkft@xxxxxxxxxx>
Closes: https://lore.kernel.org/all/CA+G9fYssasMnOE36xLH5m7ky4fKxbzN7kX5mEE7icnuu+0hGuQ@xxxxxxxxxxxxxx/
Signed-off-by: Anders Roxell <anders.roxell@xxxxxxxxxx>
---
 drivers/net/wireless/intel/iwlwifi/pcie/ctxt-info.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/net/wireless/intel/iwlwifi/pcie/ctxt-info.c b/drivers/net/wireless/intel/iwlwifi/pcie/ctxt-info.c
index cb36baac14da..1854d071aff2 100644
--- a/drivers/net/wireless/intel/iwlwifi/pcie/ctxt-info.c
+++ b/drivers/net/wireless/intel/iwlwifi/pcie/ctxt-info.c
@@ -204,9 +204,10 @@ int iwl_pcie_ctxt_info_init(struct iwl_trans *trans,
 
 	WARN_ON(RX_QUEUE_CB_SIZE(iwl_trans_get_num_rbds(trans)) > 12);
 	control_flags = IWL_CTXT_INFO_TFD_FORMAT_LONG;
-	control_flags |=
-		u32_encode_bits(RX_QUEUE_CB_SIZE(iwl_trans_get_num_rbds(trans)),
-				IWL_CTXT_INFO_RB_CB_SIZE);
+	/* This should just be u32_encode_bits() but gcc-8 and gcc-9 fail to build */
+	control_flags |= FIELD_PREP(IWL_CTXT_INFO_RB_CB_SIZE,
+		RX_QUEUE_CB_SIZE(iwl_trans_get_num_rbds(trans)) &
+		FIELD_MAX(IWL_CTXT_INFO_RB_CB_SIZE));
 	control_flags |= u32_encode_bits(rb_size, IWL_CTXT_INFO_RB_SIZE);
 	ctxt_info->control.control_flags = cpu_to_le32(control_flags);
 
-- 
2.47.2