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Subject[PATCH] firmware: arm_scmi: Eliminate local db variable in SCMI_PERF_FC_RING_DB
Date
clang warns four times:

drivers/firmware/arm_scmi/perf.c:320:24: warning: variable 'db' is
uninitialized when used within its own initialization [-Wuninitialized]
SCMI_PERF_FC_RING_DB(db, 64);
~~~~~~~~~~~~~~~~~~~~~^~~~~~~
drivers/firmware/arm_scmi/perf.c:300:31: note: expanded from macro
'SCMI_PERF_FC_RING_DB'
struct scmi_fc_db_info *db = doorbell; \
~~ ^~~~~~~~

This happens because the doorbell identifier becomes db after
preprocessing:

if (db->width == 1)
do {
u8 val = 0;
struct scmi_fc_db_info *db = db;
if (db->mask)
val = ioread8(db->addr) & db->mask;
iowrite8((u8)db->set | val, db->addr);
} while (0);

We could swap the doorbell and db identifiers within the macro and that
would resolve the issue; however, there doesn't appear to be a good
reason for having two copies of the same variable. Eliminate the one in
the do while loop to prevent this warning and make the code clearer.

Fixes: 8f12cbcb6abc ("firmware: arm_scmi: Make use SCMI v2.0 fastchannel for performance protocol")
Link: https://github.com/ClangBuiltLinux/linux/issues/635
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
---
drivers/firmware/arm_scmi/perf.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/firmware/arm_scmi/perf.c b/drivers/firmware/arm_scmi/perf.c
index 2c5201c8354c..ab946ef6b914 100644
--- a/drivers/firmware/arm_scmi/perf.c
+++ b/drivers/firmware/arm_scmi/perf.c
@@ -294,10 +294,9 @@ scmi_perf_describe_levels_get(const struct scmi_handle *handle, u32 domain,
return ret;
}

-#define SCMI_PERF_FC_RING_DB(doorbell, w) \
+#define SCMI_PERF_FC_RING_DB(db, w) \
do { \
u##w val = 0; \
- struct scmi_fc_db_info *db = doorbell; \
\
if (db->mask) \
val = ioread##w(db->addr) & db->mask; \
--
2.23.0.rc2
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