linux-kernel - Re: [PATCH v2 1/3] spi: spi-mem: add automatic poll status functions

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Date:   Mon, 17 May 2021 09:29:24 +0200
From:   Patrice CHOTARD <patrice.chotard@...s.st.com>
To:     Boris Brezillon <boris.brezillon@...labora.com>
CC:     Mark Brown <broonie@...nel.org>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Vignesh Raghavendra <vigneshr@...com>,
        <linux-mtd@...ts.infradead.org>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        <linux-spi@...r.kernel.org>,
        <linux-stm32@...md-mailman.stormreply.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <christophe.kerello@...s.st.com>
Subject: Re: [PATCH v2 1/3] spi: spi-mem: add automatic poll status functions

Hi Boris

On 5/10/21 11:22 AM, Boris Brezillon wrote:
> On Mon, 10 May 2021 10:46:48 +0200
> Patrice CHOTARD <patrice.chotard@...s.st.com> wrote:
> 
>>>   
>>>> +
>>>> +	if (ctlr->mem_ops && ctlr->mem_ops->poll_status) {
>>>> +		ret = spi_mem_access_start(mem);
>>>> +		if (ret)
>>>> +			return ret;
>>>> +
>>>> +		reinit_completion(&ctlr->xfer_completion);
>>>> +
>>>> +		ret = ctlr->mem_ops->poll_status(mem, op, mask, match,
>>>> +						 timeout_ms);
>>>> +
>>>> +		ms = wait_for_completion_timeout(&ctlr->xfer_completion,
>>>> +						 msecs_to_jiffies(timeout_ms));  
>>>
>>> Why do you need to wait here? I'd expect the poll_status to take care
>>> of this wait.  
>>
>> It was a request from Mark Brown [1]. The idea is to implement
>> similar mechanism already used in SPI framework.
> 
> Well, you have to choose, either you pass a timeout to ->poll_status()
> and let the driver wait for the status change (and return -ETIMEDOUT if
> it didn't happen in time), or you do it here and the driver only has to
> signal the core completion object. I think it's preferable to let the
> driver handle the timeout though, because you don't know how the
> status check will be implemented, and it's not like the
> reinit_completion()+wait_for_completion_timeout() done here would
> greatly simplify the drivers wait logic anyway.
> 

Ok i will remove the reinit/wait_completion() as you suggested.
Thanks
Patrice