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

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Date: Fri, 16 Feb 2024 17:19:21 +0000
From: Jonathan Cameron <jic23@...nel.org>
To: Mike Looijmans <mike.looijmans@...ic.nl>
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 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


> 
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> System Expert
> 
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