linux-kernel - Re: [PATCH v5 2/2] iio: adc: ti-ads1298: Add driver

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Date: Mon, 19 Feb 2024 07:56:49 +0100
From: Mike Looijmans <mike.looijmans@...ic.nl>
To: Jonathan Cameron <jic23@...nel.org>
CC: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
 devicetree@...r.kernel.org, linux-iio@...r.kernel.org,
 Arnd Bergmann <arnd@...nel.org>, Lars-Peter Clausen <lars@...afoo.de>,
 Liam Beguin <liambeguin@...il.com>, Liam Girdwood <lgirdwood@...il.com>,
 Maksim Kiselev <bigunclemax@...il.com>,
 Marcus Folkesson <marcus.folkesson@...il.com>,
 Marius Cristea <marius.cristea@...rochip.com>,
 Mark Brown <broonie@...nel.org>, Niklas Schnelle <schnelle@...ux.ibm.com>,
 Okan Sahin <okan.sahin@...log.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 2/2] iio: adc: ti-ads1298: Add driver

On 16-02-2024 18:19, Jonathan Cameron wrote:
> On Fri, 16 Feb 2024 17:07:49 +0100
> Mike Looijmans <mike.looijmans@...ic.nl> wrote:
>
>> On 16-02-2024 16:53, Andy Shevchenko wrote:
>>
>> ...
>>
>> +       if (reset_gpio) {
>> +               /*
>> +                * Deassert reset now that clock and power are active.
>> +                * Minimum reset pulsewidth is 2 clock cycles.
>> +                */
>> +               udelay(ADS1298_CLOCKS_TO_USECS(2));
>>
>> This is sleeping context and you are calling unsleeping function. I haven't
>> checked the macro implementation and I have no idea what is the maximum it may
>> give, but making code robust just use fsleep() call.
>>
>> It'll actually delay for 1 us (the "clock" is ~2MHz). So fsleep will compile to udelay anyway, which is fine, fsleep might get smarter in future and this would then profit.
>>
>>
>>
>> +               gpiod_set_value_cansleep(reset_gpio, 0);
>> +       } else {
>> +               ret = ads1298_write_cmd(priv, ADS1298_CMD_RESET);
>> +               if (ret)
>> +                       return dev_err_probe(dev, ret, "RESET failed\n");
>> +       }
>> +       /* Wait 18 clock cycles for reset command to complete */
>> +       udelay(ADS1298_CLOCKS_TO_USECS(18));
>>
>> Ditto.
>>
>> ...
>>
>>
>> If it's the only issue I think Jonathan can modify when applying
>> (no new patch version would be needed).
>>
>> That'd be nice.
> ok.  As this is still the top of my tree I'll just tweak it.
>
> Does anyone else read fsleep as femtosecond sleep every time? :)
> Maybe computers will go that fast one day.
>
> Jonathan

Noticed this triggered a kernel test robot report. Sent a v6 that fixes 
the bug.

Can also make it a separate patch if you prefer, in that case ignore v6.


-- 
Mike Looijmans
System Expert

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