Hi Nathan,
On 13/06/2019 23:12, Nathan Huckleberry wrote: > 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. All the code seems broken regarding the negative value shifting as the macros pass an integer: eg. tsc->coef.a2 = FIXPT_DIV(FIXPT_INT(thcode[1] - thcode[0]), tsc->tj_t - FIXPT_INT(ths_tj_1)); thcode[1] is always < than thcode[0], thcode[1] - thcode[0] < 0 FIXPT_INT(thcode[1] - thcode[0]) is undefined Is it done on purpose FIXPT_DIV(FIXPT_INT(thcode[1] - thcode[0]) ? Try developing the macro with the coef.a2 computation ... The code quality of this driver could be better, it deserves a rework IMHO ... I suggest to revert: 4eb39f79ef443fa566d36bd43f1f578d5c140305 bdc4480a669d476814061b4da6bb006f7048c8e5 6a310f8f97bb8bc2e2bb9db6f49a1b8678c8d144 Rework the coefficient computation and re-introduce what was reverted in a nicer way. > Fixes: 4eb39f79ef44 ("thermal: rcar_gen3_thermal: Update value of Tj_1") > Cc: clang-built-li...@googlegroups.com > Link: https://github.com/ClangBuiltLinux/linux/issues/531 > Signed-off-by: Nathan Huckleberry <nh...@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)); > -- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog