linux-kernel - Re: [PATCH 2/3] iio: pressure: Support ROHM BU1390

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Message-ID: <4084c827-abf6-0f15-7957-13db50912943@gmail.com>
Date:   Mon, 18 Sep 2023 14:42:11 +0300
From:   Matti Vaittinen <mazziesaccount@...il.com>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Angel Iglesias <ang.iglesiasg@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Andreas Klinger <ak@...klinger.de>, linux-iio@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] iio: pressure: Support ROHM BU1390

On 9/17/23 12:26, Jonathan Cameron wrote:
> On Thu, 14 Sep 2023 14:47:44 +0300
> Matti Vaittinen <mazziesaccount@...il.com> wrote:
> 
>> On 9/10/23 16:22, Jonathan Cameron wrote:
>>> On Wed, 6 Sep 2023 15:37:48 +0300
>>> Matti Vaittinen <mazziesaccount@...il.com> wrote:
>>>    
>>>> Support for the ROHM BM1390 pressure sensor. The BM1390GLV-Z can measure
>>>> pressures ranging from 300 hPa to 1300 hPa with configurable measurement
>>>> averaging and internal FIFO. The sensor does also provide temperature
>>>> measurements.
>>>>
>>>> Sensor does also contain IIR filter implemented in HW. The data-sheet
>>>> says the IIR filter can be configured to be "weak", "middle" or
>>>> "strong". Some RMS noise figures are provided in data sheet but no
>>>> accurate maths for the filter configurations is provided. Hence, the IIR
>>>> filter configuration is not supported by this driver and the filter is
>>>> configured to the "middle" setting (at least not for now).
>>
>>>> +
>>>> +static irqreturn_t bm1390_irq_thread_handler(int irq, void *private)
>>>> +{
>>>> +	struct iio_dev *idev = private;
>>>> +	struct bm1390_data *data = iio_priv(idev);
>>>> +	int ret = IRQ_NONE;
>>>> +
>>>> +	mutex_lock(&data->mutex);
>>>> +
>>>> +	if (data->trigger_enabled) {
>>>> +		iio_trigger_poll_nested(data->trig);
>>>> +		ret = IRQ_HANDLED;
>>>> +	}
>>>> +
>>>> +	if (data->state == BM1390_STATE_FIFO) {
>>>
>>> Can this and trigger_enabled be true?
>>
>> Thanks for asking this question. Intention was that these are mutually
>> exclusive. However, I think that the check
>> if (iio_device_get_current_mode(idev) == INDIO_BUFFER_TRIGGERED)
>> in bm1390_buffer_postenable(), before calling the bm1390_fifo_enable()
>> is not 100% race free.
>>
>> I, however, like the idea of having this check in the buffer-enable
>> function - I think it makes the design much more obvious. What I will do
>> is adding another check for:
>> 	if (data->trigger_enable) {
>> 		ret = -EBUSY;
>> 		goto unlock_out;
>> 	}
>>
>> inside the bm1390_fifo_enable() to the section which holds the mutex.
> 
> You could make the exclusive nature obvious in the thread_handler by using an
> else if () above.

Right. Thanks.

> 
>>
>>
>> Yours,
>> 	-- Matti
>>
>>
>>
> 

-- 
Matti Vaittinen
Linux kernel developer at ROHM Semiconductors
Oulu Finland

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