[PATCH] thermal: rcar_gen3_thermal: Fix Wshift-negative-value

Nathan Huckleberry
2019-06-13T21:12:49Z

Clang produces the following warning

vers/thermal/rcar_gen3_thermal.c:147:33: warning: shifting a negative
signed value is undefined [-Wshift-negative-value] / (ptat[0] - ptat[2])) +
FIXPT_INT(TJ_3); ^~~~~~~~~~~~~~~ drivers/thermal/rcar_gen3_thermal.c:126:29
note: expanded from macro 'FIXPT_INT' #define FIXPT_INT(_x) ((_x) <<
FIXPT_SHIFT) ~~~~ ^ drivers/thermal/rcar_gen3_thermal.c:150:18: warning:
shifting a negative signed value is undefined [-Wshift-negative-value]
tsc->tj_t - FIXPT_INT(TJ_3)); ~~~~~~~~~~~~^~~~~~~~~~~~~~~~

Upon further investigating it looks like there is no real reason for
TJ_3 to be -41. Usages subtract -41, code would be cleaner to just add.

Fixes: 4eb39f79ef44 ("thermal: rcar_gen3_thermal: Update value of Tj_1")
Cc: clang-built-linux@googlegroups.com
Link: https://github.com/ClangBuiltLinux/linux/issues/531
Signed-off-by: Nathan Huckleberry <nhuck@google.com>
---
drivers/thermal/rcar_gen3_thermal.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/thermal/rcar_gen3_thermal.c b/drivers/thermal/rcar_gen3_thermal.c
index a56463308694..f4b4558c08e9 100644
--- a/drivers/thermal/rcar_gen3_thermal.c
+++ b/drivers/thermal/rcar_gen3_thermal.c
@@ -131,7 +131,7 @@ static inline void rcar_gen3_thermal_write(struct rcar_gen3_thermal_tsc *tsc,
#define RCAR3_THERMAL_GRAN 500 /* mili Celsius */

/* no idea where these constants come from */
-#define TJ_3 -41
+#define TJ_3 41

static void rcar_gen3_thermal_calc_coefs(struct rcar_gen3_thermal_tsc *tsc,
int *ptat, const int *thcode,
@@ -144,11 +144,11 @@ static void rcar_gen3_thermal_calc_coefs(struct rcar_gen3_thermal_tsc *tsc,
* the dividend (4095 * 4095 << 14 > INT_MAX) so keep it unscaled
*/
tsc->tj_t = (FIXPT_INT((ptat[1] - ptat[2]) * 157)
- / (ptat[0] - ptat[2])) + FIXPT_INT(TJ_3);
+ / (ptat[0] - ptat[2])) - FIXPT_INT(TJ_3);

tsc->coef.a1 = FIXPT_DIV(FIXPT_INT(thcode[1] - thcode[2]),
- tsc->tj_t - FIXPT_INT(TJ_3));
- tsc->coef.b1 = FIXPT_INT(thcode[2]) - tsc->coef.a1 * TJ_3;
+ tsc->tj_t + FIXPT_INT(TJ_3));
+ tsc->coef.b1 = FIXPT_INT(thcode[2]) + tsc->coef.a1 * TJ_3;

tsc->coef.a2 = FIXPT_DIV(FIXPT_INT(thcode[1] - thcode[0]),
tsc->tj_t - FIXPT_INT(ths_tj_1));
--
2.22.0.rc2.383.gf4fbbf30c2-goog