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From:   Billy Tsai <billy_tsai@aspeedtech.com>
To:     Andrew Jeffery <andrew@aj.id.au>,
        Jonathan Cameron <jic23@kernel.org>,
        "lars@metafoo.de" <lars@metafoo.de>, Joel Stanley <joel@jms.id.au>,
        "linux-iio@vger.kernel.org" <linux-iio@vger.kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "linux-aspeed@lists.ozlabs.org" <linux-aspeed@lists.ozlabs.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Potin Lai <Potin.Lai@quantatw.com>,
        "patrickw3@meta.com" <patrickw3@meta.com>
Subject: Re: [PATCH v1] iio: adc: aspeed: Support deglitch feature.
Thread-Topic: [PATCH v1] iio: adc: aspeed: Support deglitch feature.
Thread-Index: AQHZ74jrjlOSMsUvo0yNgHQbGiIz5LAviZQAgAamlbSAAX0ygIACRq65
Date:   Wed, 4 Oct 2023 17:44:12 +0000
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=0A=
>>> > Create event sysfs for applying the deglitch condition. When=0A=
>>> > in_voltageY_thresh_rising_en/in_voltageY_thresh_falling_en is set to =
true,=0A=
>>> > the driver will use the in_voltageY_thresh_rising_value and=0A=
>>> > in_voltageY_thresh_falling_value as threshold values. If the ADC valu=
e=0A=
>>> > falls outside this threshold, the driver will wait for the ADC sampli=
ng=0A=
>>> > period and perform an additional read once to achieve the deglitching=
=0A=
>>> > purpose.=0A=
>>> >=0A=
>>> > Signed-off-by: Billy Tsai <billy_tsai@aspeedtech.com>=0A=
>>> > ---=0A=
>>> >  drivers/iio/adc/aspeed_adc.c | 193 +++++++++++++++++++++++++++++++++=
+-=0A=
>>> >  1 file changed, 189 insertions(+), 4 deletions(-)=0A=
>>> >=0A=
>>> > diff --git a/drivers/iio/adc/aspeed_adc.c b/drivers/iio/adc/aspeed_ad=
c.c=0A=
>>> > index 998e8bcc06e1..9e746c81d916 100644=0A=
>>> > --- a/drivers/iio/adc/aspeed_adc.c=0A=
>>> > +++ b/drivers/iio/adc/aspeed_adc.c=0A=
>>> > @@ -95,6 +95,7 @@ struct aspeed_adc_model_data {=0A=
>>> >       bool wait_init_sequence;=0A=
>>> >       bool need_prescaler;=0A=
>>> >       bool bat_sense_sup;=0A=
>>> > +     bool require_extra_eoc;=0A=
>>=0A=
>>> What is "eoc"? Can we use a better name or add an explanatory comment?=
=0A=
>>=0A=
>> Hi Andrew,=0A=
>> This is the signal name for our ADC controller, it means "End Of=0A=
>> Conversion".=0A=
>> The appearance of this signal period indicates that the ADC value is=0A=
>> valid and being updated to the register.=0A=
=0A=
> Okay, searching for "conversion" in the datasheet didn't turn up anything=
 like this. It seems I wasn't off-track with asking. If you go forward with=
 the patch in some manner, can you add a comment to the code documenting th=
e meaning of 'eoc'?=0A=
=0A=
Okay, I will add the comment for the meaning of eoc.=0A=
=0A=
>=0A=
>> >       /* Register ADC clock prescaler with source specified by device =
tree.=0A=
>> > */=0A=
>> >       spin_lock_init(&data->clk_lock);=0A=
>> >       snprintf(clk_parent_name, ARRAY_SIZE(clk_parent_name), "%s",=0A=
>> > @@ -632,7 +806,14 @@ static int aspeed_adc_probe(struct platform_devic=
e=0A=
>> > *pdev)=0A=
>> >       adc_engine_control_reg_val |=3D ASPEED_ADC_CTRL_CHANNEL;=0A=
>> >       writel(adc_engine_control_reg_val,=0A=
>> >              data->base + ASPEED_REG_ENGINE_CONTROL);=0A=
>> > -=0A=
>> > +     adc_engine_control_reg_val =3D=0A=
>> > +             FIELD_GET(ASPEED_ADC_CTRL_CHANNEL,=0A=
>> > +                       readl(data->base + ASPEED_REG_ENGINE_CONTROL))=
;=0A=
>> > +     data->required_eoc_num =3D hweight_long(adc_engine_control_reg_v=
al);=0A=
>> > +     if (data->model_data->require_extra_eoc &&=0A=
>> > +         (adc_engine_control_reg_val &=0A=
>> > +          BIT(data->model_data->num_channels - 1)))=0A=
>> > +             data->required_eoc_num +=3D 12;=0A=
>=0A=
>> Why 12? Why add a value to the number of engines enabled? Have I misunde=
rstood?=0A=
>=0A=
> This behavior is specified by the hardware. In our ADC, it requires 12=0A=
> dummy sampling=0A=
> periods to switch the sampling channel from CH7 to CH0. Hence, this=0A=
> condition checks=0A=
> the enable status of channel 7 to determine the necessary delay period=0A=
> for obtaining the=0A=
> updated ADC values for each channel.=0A=
=0A=
> Okay, I feel using a magic value '12' with what you wrote above as an exp=
lanation is asking a bit much of the reader. Again, if you go forward with =
this patch in some fashion, can you document the meaning of 12 in a comment=
 (and possibly use a macro to name it)?=0A=
=0A=
Okay, I will include comments and use meaningful macro to name it.=0A=
=0A=
Thanks=