linux-kernel - Re: [PATCH] thermal: rockchip: fix handling of invalid readings

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Date:	Mon, 10 Aug 2015 14:30:57 +0800
From:	Caesar Wang <wxt@...k-chips.com>
To:	Dmitry Torokhov <dtor@...omium.org>,
	Heiko Stuebner <heiko@...ech.de>
CC:	Eduardo Valentin <edubezval@...il.com>, dianders@...omium.org,
	linux-pm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] thermal: rockchip: fix handling of invalid readings

Dear Dmitry,

Thanks your patch.

The code looks like fine,but I don't think the TS-ADC will work on 
rk3288 SoC.

在 2015年08月08日 04:59, Dmitry Torokhov 写道:
> We attempted to signal invalid code by returning -EAGAIN from
> rk_tsadcv2_code_to_temp(), unfortunately the return value was stuffed
> directly into the temperature pointer, potentially confusing upper
> layers with temperature of -EINVAL.
>
> Let's split temperature from error/success indicator to avoid such
> confusion.
>
> Also change the way we scan the temperature table to start with the 2nd
> element so that we do not need to worry that we may reference out of
> bounds element while doing binary search and keep checking that we end
> up with 'mid' equal to 0 (since we are looking for the temperature that
> would fall into interval between the 'mid' and 'mid - 1') .
>
> Signed-off-by: Dmitry Torokhov <dtor@...omium.org>
> ---
>   drivers/thermal/rockchip_thermal.c | 28 +++++++++++++---------------
>   1 file changed, 13 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/thermal/rockchip_thermal.c b/drivers/thermal/rockchip_thermal.c
> index c89ffb2..93ee307 100644
> --- a/drivers/thermal/rockchip_thermal.c
> +++ b/drivers/thermal/rockchip_thermal.c
> @@ -124,7 +124,7 @@ struct rockchip_thermal_data {
>   #define TSADCV2_AUTO_PERIOD_HT_TIME		50  /* msec */
>   
>   struct tsadc_table {
> -	unsigned long code;
> +	u32 code;
>   	long temp;
>   };
>   
> @@ -164,7 +164,6 @@ static const struct tsadc_table v2_code_table[] = {
>   	{3452, 115000},
>   	{3437, 120000},
>   	{3421, 125000},
> -	{0, 125000},
>   };
>   
>   static u32 rk_tsadcv2_temp_to_code(long temp)
> @@ -191,19 +190,21 @@ static u32 rk_tsadcv2_temp_to_code(long temp)
>   	return 0;
>   }
>   
> -static int rk_tsadcv2_code_to_temp(u32 code)
> +static int rk_tsadcv2_code_to_temp(u32 code, int *temp)
>   {
> -	unsigned int low = 0;
> +	unsigned int low = 1;
>   	unsigned int high = ARRAY_SIZE(v2_code_table) - 1;
>   	unsigned int mid = (low + high) / 2;
>   	unsigned int num;
>   	unsigned long denom;
>   
> -	/* Invalid code, return -EAGAIN */
> -	if (code > TSADCV2_DATA_MASK)
> -		return -EAGAIN;
> +	BUILD_BUG_ON(ARRAY_SIZE(v2_code_table) < 2);
>   
> -	while (low <= high && mid) {
> +	code &= TSADCV2_DATA_MASK;
> +	if (code < v2_code_table[high].code)
> +		return -EAGAIN;		/* Incorrect reading */
> +
> +	while (low <= high) {
>   		if (code >= v2_code_table[mid].code &&
>   		    code < v2_code_table[mid - 1].code)
>   			break;
> @@ -223,7 +224,9 @@ static int rk_tsadcv2_code_to_temp(u32 code)
>   	num = v2_code_table[mid].temp - v2_code_table[mid - 1].temp;
>   	num *= v2_code_table[mid - 1].code - code;
>   	denom = v2_code_table[mid - 1].code - v2_code_table[mid].code;
> -	return v2_code_table[mid - 1].temp + (num / denom);
> +	*temp = v2_code_table[mid - 1].temp + (num / denom);
> +
> +	return 0;
>   }
>   
>   /**
> @@ -281,14 +284,9 @@ static int rk_tsadcv2_get_temp(int chn, void __iomem *regs, int *temp)
>   {
>   	u32 val;
>   
> -	/* the A/D value of the channel last conversion need some time */
>   	val = readl_relaxed(regs + TSADCV2_DATA(chn));
> -	if (val == 0)
> -		return -EAGAIN;
> -

if we reserve the above code, that will get the ADC value.

> -	*temp = rk_tsadcv2_code_to_temp(val);
>   
> -	return 0;
> +	return rk_tsadcv2_code_to_temp(val, temp);
>   }
>   
>   static void rk_tsadcv2_tshut_temp(int chn, void __iomem *regs, long temp)


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