On Thu 26 Jul 03:33 PDT 2018, Amit Kucheria wrote:
> The current code will always return 0xffffffff in case of negative
> temperatures due to a bug in how the binary sign extension is being done.
>
> Use sign_extend32() instead.
>
> Signed-off-by: Amit Kucheria <amit.kucheria@xxxxxxxxxx>
> Reviewed-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
Reviewed-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>
Regards,
Bjorn
> ---
> drivers/thermal/qcom/tsens-v2.c | 13 +++++--------
> 1 file changed, 5 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/thermal/qcom/tsens-v2.c b/drivers/thermal/qcom/tsens-v2.c
> index 908e3dcb2d5c..44da02f594ac 100644
> --- a/drivers/thermal/qcom/tsens-v2.c
> +++ b/drivers/thermal/qcom/tsens-v2.c
> @@ -5,19 +5,20 @@
> */
>
> #include <linux/regmap.h>
> +#include <linux/bitops.h>
> #include "tsens.h"
>
> #define STATUS_OFFSET 0xa0
> #define LAST_TEMP_MASK 0xfff
> #define STATUS_VALID_BIT BIT(21)
> -#define CODE_SIGN_BIT BIT(11)
>
> static int get_temp_tsens_v2(struct tsens_device *tmdev, int id, int *temp)
> {
> struct tsens_sensor *s = &tmdev->sensor[id];
> u32 code;
> unsigned int status_reg;
> - int last_temp = 0, last_temp2 = 0, last_temp3 = 0, ret;
> + u32 last_temp = 0, last_temp2 = 0, last_temp3 = 0;
> + int ret;
>
> status_reg = tmdev->tm_offset + STATUS_OFFSET + s->hw_id * 4;
> ret = regmap_read(tmdev->map, status_reg, &code);
> @@ -54,12 +55,8 @@ static int get_temp_tsens_v2(struct tsens_device *tmdev, int id, int *temp)
> else if (last_temp2 == last_temp3)
> last_temp = last_temp3;
> done:
> - /* Code sign bit is the sign extension for a negative value */
> - if (last_temp & CODE_SIGN_BIT)
> - last_temp |= ~CODE_SIGN_BIT;
> -
> - /* Temperatures are in deciCelicius */
> - *temp = last_temp * 100;
> + /* Convert temperature from deciCelsius to milliCelsius */
> + *temp = sign_extend32(last_temp, fls(LAST_TEMP_MASK) - 1) * 100;
>
> return 0;
> }
> --
> 2.17.GIT
>
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