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

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Date:   Wed, 5 May 2021 09:21:15 +0200
From:   Patrice CHOTARD <patrice.chotard@...s.st.com>
To:     Mark Brown <broonie@...nel.org>
CC:     Pratyush Yadav <p.yadav@...com>,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Boris Brezillon <boris.brezillon@...labora.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 1/3] spi: spi-mem: add automatic poll status functions

Hi Mark

On 4/30/21 5:56 PM, Mark Brown wrote:
> On Fri, Apr 30, 2021 at 04:22:34PM +0200, Patrice CHOTARD wrote:
>> On 4/26/21 6:51 PM, Mark Brown wrote:
>>> On Mon, Apr 26, 2021 at 09:56:12PM +0530, Pratyush Yadav wrote:
> 
>>> Is it possible there's some situation where you're waiting for some bits
>>> to clear as well?
> 
>> Yes, we are waiting STATUS_BUSY bit to be cleared, see patch 2 which is making 
>> usage of this API.
> 
> Then the inverse question applies - is there no circumstance where we
> might be waiting for a bit to be set?
> 
>>> We already have the core handling other timeouts.  We don't pass around
>>> completions but rather have an API function that the driver has to call
>>> when the operation completes, a similar pattern might work here.  Part
> 
>> So, if i correctly understood, you make allusion to what is already done
>> in SPI core framework with spi_finalize_current_transfer() right ?
> 
> Yes, and _current_message().
> 
>>> of the thing with those APIs which I'm missing here is that this will
>>> just return -EOPNOTSUPP if the driver can't do the delay in hardware, I
>>> think it would be cleaner if this API were similar and the core dealt
>>> with doing the delay/poll on the CPU.  That way the users don't need to
>>> repeat the handling for the offload/non-offload cases.
> 
>> Sorry, i didn't catch what you mean here. In PATCH 2, that's the case,
>> if spi_mem_poll_status() is not supported, the core is dealing with 
>> the delay/poll on the CPU in spinand_wait().
> 
> That's in the NAND core, not in spi-mem.  Any other users of spi-mem
> will also need to open code stuff.
> 

Ok, got it, i will transfer what is done in spi_nand_wait() into spi_mem_poll_status() 
in order to get the full feature in spi-mem which will profit to all spi-mem users as requested.

Thanks
Patrice