linux-kernel - Re: [PATCH 08/13] thermal/drivers/hisi: Fix configuration register setting

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Date:   Mon, 4 Sep 2017 11:16:55 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Leo Yan <leo.yan@...aro.org>
Cc:     rui.zhang@...el.com, edubezval@...il.com, linux-pm@...r.kernel.org,
        kevin.wangtao@...aro.org, open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 08/13] thermal/drivers/hisi: Fix configuration register
 setting

On 04/09/2017 02:58, Leo Yan wrote:
> On Sat, Sep 02, 2017 at 10:34:34AM +0200, Daniel Lezcano wrote:
>> On 02/09/2017 04:54, Leo Yan wrote:
>>> On Wed, Aug 30, 2017 at 10:47:32AM +0200, Daniel Lezcano wrote:
>>>> The TEMP0_CFG configuration register contains different field to set up the
>>>> temperature controller. However in the code, nothing prevents a setup to
>>>> overwrite the previous one: eg. writing the hdak value overwrites the sensor
>>>> selection, the sensor selection overwrites the hdak value.
>>>>
>>>> In order to prevent such thing, use a regmap-like mechanism by reading the
>>>> value before, set the corresponding bits and write the result.
>>>>
>>>> Signed-off-by: Daniel Lezcano <daniel.lezcano@...aro.org>
>>>> ---
>>>>  drivers/thermal/hisi_thermal.c | 30 +++++++++++++++++++++++++-----
>>>>  1 file changed, 25 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/drivers/thermal/hisi_thermal.c b/drivers/thermal/hisi_thermal.c
>>>> index d77a938..3e03908 100644
>>>> --- a/drivers/thermal/hisi_thermal.c
>>>> +++ b/drivers/thermal/hisi_thermal.c
>>>> @@ -132,19 +132,39 @@ static inline void hisi_thermal_enable(void __iomem *addr, int value)
>>>>  	writel(value, addr + TEMP0_EN);
>>>>  }
>>>>  
>>>> -static inline void hisi_thermal_sensor_select(void __iomem *addr, int sensor)
>>>> +static inline int hisi_thermal_get_temperature(void __iomem *addr)
>>>>  {
>>>> -	writel((sensor << 12), addr + TEMP0_CFG);
>>>> +	return hisi_thermal_step_to_temp(readl(addr + TEMP0_VALUE));
>>>>  }
>>>>  
>>>> -static inline int hisi_thermal_get_temperature(void __iomem *addr)
>>>> +/*
>>>> + * Temperature configuration register - Sensor selection
>>>> + *
>>>> + * Bits [19:12]
>>>> + *
>>>> + * 0x0: local sensor (default)
>>>> + * 0x1: remote sensor 1 (ACPU cluster 1)
>>>> + * 0x2: remote sensor 2 (ACPU cluster 0)
>>>> + * 0x3: remote sensor 3 (G3D)
>>>> + */
>>>> +static inline void hisi_thermal_sensor_select(void __iomem *addr, int sensor)
>>>>  {
>>>> -	return hisi_thermal_step_to_temp(readl(addr + TEMP0_VALUE));
>>>> +	writel(readl(addr + TEMP0_CFG) | (sensor << 12), addr + TEMP0_CFG);
>>>
>>> nitpick: maybe it's better to firstly clear related bits and then set
>>> value?
>>
>> Sorry, I don't get the comment. Can you elaborate ?
> 
> Sure, here I am bit concern there the mixing old bits value and new
> setting bits. My suggested code likes below:
> 
>   u32 val;
> 
>   val = readl(addr + TEMP0_CFG);
>   val &= ~0xF000;
>   val |= (sensor << 12);
>   writel(val, addr + TEMP0_CFG);

Oh, yes. Good catch.


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