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

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Message-ID: <20210430155623.GD5981@sirena.org.uk>
Date:   Fri, 30 Apr 2021 16:56:23 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Patrice CHOTARD <patrice.chotard@...s.st.com>
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

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.

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