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Date:   Thu, 26 Jul 2018 09:41:32 -0700
From:   Bjorn Andersson <bjorn.andersson@linaro.org>
To:     Amit Kucheria <amit.kucheria@linaro.org>
Cc:     linux-kernel@vger.kernel.org, rnayak@codeaurora.org,
        linux-arm-msm@vger.kernel.org, edubezval@gmail.com,
        smohanad@codeaurora.org, andy.gross@linaro.org,
        dianders@chromium.org, mka@chromium.org,
        Zhang Rui <rui.zhang@intel.com>, linux-pm@vger.kernel.org
Subject: Re: [PATCH v2 3/3] thermal: tsens: Fix negative temperature reporting
Message-ID: <20180726164132.GC5450@tuxbook-pro>
References: <cover.1532600791.git.amit.kucheria@linaro.org>
 <52516c287c9455676e7cbde4a4fa94282d73367f.1532600791.git.amit.kucheria@linaro.org>
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In-Reply-To: <52516c287c9455676e7cbde4a4fa94282d73367f.1532600791.git.amit.kucheria@linaro.org>
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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@linaro.org>
> Reviewed-by: Matthias Kaehlcke <mka@chromium.org>

Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>

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
>