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Date:   Sat, 16 Sep 2017 18:14:08 +0800
From:   icenowy@...c.io
To:     Quentin Schulz <quentin.schulz@...e-electrons.com>
Cc:     Lee Jones <lee.jones@...aro.org>, Rob Herring <robh+dt@...nel.org>,
        Maxime Ripard <maxime.ripard@...e-electrons.com>,
        Chen-Yu Tsai <wens@...e.org>,
        Jonathan Cameron <jic23@...nel.org>,
        devicetree@...r.kernel.org, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-sunxi@...glegroups.com,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v4 4/6] iio: adc: sun4i-gpadc-iio: add support for H3
 thermal sensor

在 2017-09-16 17:45,Quentin Schulz 写道:
> Hi Icenowy,
> 
> On 14/09/2017 16:52, Icenowy Zheng wrote:
>> This adds support for the Allwinner H3 thermal sensor.
>> 
>> Allwinner H3 has a thermal sensor like the one in A33, but have its
>> registers nearly all re-arranged, sample clock moved to CCU and a pair
>> of bus clock and reset added. It's also the base of newer SoCs' 
>> thermal
>> sensors.
>> 
>> The thermal sensors on A64 and H5 is like the one on H3, but with of
>> course different formula factors.
>> 
>> Signed-off-by: Icenowy Zheng <icenowy@...c.io>
>> ---
>> Changes in v4:
>> - Splitted out some code refactors.
>> - Code sequence changed back. (The gpadc_data went back to the start 
>> of
>>   the source file)
>> 
>>  drivers/iio/adc/sun4i-gpadc-iio.c | 48 
>> +++++++++++++++++++++++++++++++++++++++
>>  include/linux/mfd/sun4i-gpadc.h   | 27 ++++++++++++++++++++++
>>  2 files changed, 75 insertions(+)
> [...]
>> diff --git a/include/linux/mfd/sun4i-gpadc.h 
>> b/include/linux/mfd/sun4i-gpadc.h
>> index 78d31984a222..5c2a12101052 100644
>> --- a/include/linux/mfd/sun4i-gpadc.h
>> +++ b/include/linux/mfd/sun4i-gpadc.h
> [...]
>> +#define SUN8I_H3_GPADC_CTRL2_T_ACQ1(x)			((GENMASK(15, 0) * (x)) << 
>> 16)
>> +
> 
> You want to replace * by &.
> 
> ((GENMASK(15, 0) & (x)) << 16)
> 
> Would ((GENMASK(31, 16) & ((x) << 16)) make the bits you set even more
> obvious?
> 
>>  #define SUN4I_GPADC_CTRL3				0x0c
>> +/*
>> + * This register is named "Average filter Control Register" in H3 
>> Datasheet,
>> + * but the register's definition is the same as the old CTRL3 
>> register.
>> + */
>> +#define SUN8I_H3_GPADC_CTRL3				0x70
>> 
> 
> I would name it as it is in the documentation:
> SUN8I_H3_THS_FILTER

The definition of this register is the same as the CTRL3.

Maybe this name is better, but the similarity between them still needs
to be documented, as the SUN4I_GPADC_CTRL3_XXX macros will be used to
populate this register.

> 
> No need for comments then.
> 
>>  #define SUN4I_GPADC_CTRL3_FILTER_EN			BIT(2)
>>  #define SUN4I_GPADC_CTRL3_FILTER_TYPE(x)		(GENMASK(1, 0) & (x))
>> @@ -71,6 +84,13 @@
>>  #define SUN4I_GPADC_INT_FIFOC_TP_UP_IRQ_EN		BIT(1)
>>  #define SUN4I_GPADC_INT_FIFOC_TP_DOWN_IRQ_EN		BIT(0)
>> 
>> +#define SUN8I_H3_GPADC_INTC				0x44
>> +
>> +#define SUN8I_H3_GPADC_INTC_TEMP_PERIOD(x)		((GENMASK(19, 0) & (x)) 
>> << 12)
>> +#define SUN8I_H3_GPADC_INTC_TEMP_DATA			BIT(8)
>> +#define SUN8I_H3_GPADC_INTC_TEMP_SHUT			BIT(4)
>> +#define SUN8I_H3_GPADC_INTC_TEMP_ALARM			BIT(0)
>> +
> 
> Since it isn't an ADC anymore but rather just a THS, why don't you use
> SUN8I_H3_THS instead of SUN8I_H3_GPADC? That way, it also matches the
> datasheet.
> 
>>  #define SUN4I_GPADC_INT_FIFOS				0x14
>> 
>>  #define SUN4I_GPADC_INT_FIFOS_TEMP_DATA_PENDING		BIT(18)
>> @@ -80,9 +100,16 @@
>>  #define SUN4I_GPADC_INT_FIFOS_TP_UP_PENDING		BIT(1)
>>  #define SUN4I_GPADC_INT_FIFOS_TP_DOWN_PENDING		BIT(0)
>> 
>> +#define SUN8I_H3_GPADC_INTS				0x44
> 
> 0x48
> 
> [...]
> 
> 1) You're not using irqs, why would you define registers that will 
> never
> be used?

I will then rework it to use IRQs, but not now.

Maybe I should add it when I use them?

> 
> 2) Why aren't you using irqs? I remember we discussed on IRC that you
> had some problems with the H3 when resuming or when probing the driver.
> The register would have a zero in it until you have a first sample that
> arrived (i.e. after the sample rate you set with T_ACQ) that would make
> the thermal framework panic since the thermal sensor would return
> something way too hot and shutdown your board?

Nope, it's another problem -- the runtime resume function is even not
called before the first sample, and the first sample will happen when
the THS is still suspended.

> 
> The H3 apparently supports IRQs, why do you not support them for the
> temperature? They might be broken as it is on A33 but then it might be 
> a
> good idea to write it down in a comment in the driver (and not adding
> the unused registers in the header file) or at least in the commit log.
> 
> 3) Now that you have support for clocks, wouldn't it be a good idea to
> disable them during suspend?

Interesting... It's meaningful to disable the mod clock during suspend.

> 
> Thanks,
> Quentin

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