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Message-ID: <e04ca010-289c-4216-95ea-2f2418613378@topic.nl>
Date: Tue, 6 Feb 2024 16:44:03 +0100
From: Mike Looijmans <mike.looijmans@...ic.nl>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
CC: devicetree@...r.kernel.org, linux-iio@...r.kernel.org,
Jonathan Cameron <jic23@...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 v3 2/2] iio: adc: ti-ads1298: Add driver
On 06-02-2024 16:09, Andy Shevchenko wrote:
> On Tue, Feb 06, 2024 at 03:47:45PM +0100, Mike Looijmans wrote:
>> On 06-02-2024 15:25, Mike Looijmans wrote:
>>> On 06-02-2024 14:50, Andy Shevchenko wrote:
>>>> On Tue, Feb 06, 2024 at 02:33:47PM +0100, Mike Looijmans wrote:
>>>>> On 06-02-2024 13:57, Andy Shevchenko wrote:
>>>>>> On Tue, Feb 06, 2024 at 07:58:18AM +0100, Mike Looijmans wrote:
> ...
>
>>>>>>> + wasbusy = --priv->rdata_xfer_busy;
>>>>>> Why preincrement? How would it be different from postincrement?
>>>>> Maybe better write this as:
>>>>>
>>>>> --priv->rdata_xfer_busy;
>>>>>
>>>>> wasbusy = priv->rdata_xfer_busy;
>>>>>
>>>>> I want the value after decrementing it.
>>>> Yes, looks more obvious.
>>> Having done that, and looking at it again, it's better to just eliminate
>>> the local "wasbusy" altogether. More concise.
>>
>> This removes the decrement operator, so the method now looks like this:
>>
>>
>> static void ads1298_rdata_release_busy_or_restart(struct ads1298_private
>> *priv)
>> {
>> guard(spinlock_irqsave)(&priv->irq_busy_lock);
>>
>> if (priv->rdata_xfer_busy > 1) {
>> /*
>> * DRDY interrupt occurred before SPI completion. Start a new
>> * SPI transaction now to retrieve the data that wasn't latched
>> * into the ADS1298 chip's transfer buffer yet.
>> */
>> spi_async(priv->spi, &priv->rdata_msg);
>> /*
>> * If more than one DRDY took place, there was an overrun. Since
>> * the sample is already lost, reset the counter to 1 so that
>> * we will wait for a DRDY interrupt after this SPI transaction.
>> */
>> priv->rdata_xfer_busy = 1;
>> } else {
>> /* No pending data, wait for DRDY */
>> priv->rdata_xfer_busy = 0;
>> }
>> }
> Yep and it looks like you reinvented atomics :-)
>
> atomic_t rdata_xfer_busy;
> ...
>
> But it's up to you what to do with that.
> Maybe Jonathan can advice something different.
>
The spinlock also protects the call to spi_async().
--
Mike Looijmans
System Expert
TOPIC Embedded Products B.V.
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