linux-kernel - Re: [PATCH v3 3/6] spi: sun6i: restrict transfer length in PIO-mode

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Message-ID: <20180409092730.2moyhl5aaktjwbyn@flea>
Date:   Mon, 9 Apr 2018 11:27:30 +0200
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Sergey Suloev <ssuloev@...altech.com>
Cc:     Mark Brown <broonie@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-spi@...r.kernel.org
Subject: Re: [PATCH v3 3/6] spi: sun6i: restrict transfer length in PIO-mode

On Fri, Apr 06, 2018 at 06:48:23PM +0300, Sergey Suloev wrote:
> On 04/06/2018 10:34 AM, Maxime Ripard wrote:
> > On Thu, Apr 05, 2018 at 04:44:16PM +0300, Sergey Suloev wrote:
> > > On 04/05/2018 04:17 PM, Mark Brown wrote:
> > > > On Thu, Apr 05, 2018 at 12:59:35PM +0300, Sergey Suloev wrote:
> > > > > On 04/05/2018 12:19 PM, Maxime Ripard wrote:
> > > > > > The point of that patch was precisely to allow to send more data than
> > > > > > the FIFO. You're breaking that behaviour without any justification,
> > > > > > and this is not ok.
> > > > > I am sorry, but you can't. That's a hardware limitation.
> > > > Are you positive about that?  Normally you can add things to hardware
> > > > FIFOs while they're being drained so so long as you can keep data
> > > > flowing in at least as fast as it's being consumed.
> > > Well, normally yes, but this is not the case with the hardware that I own.
> > > My a20 (BPiM1+) and a31 (BPiM2) boards behaves differently. With a transfer
> > > larger than FIFO then TC interrupt never happens.
> > Because you're not supposed to have a transfer larger than the FIFO,
> > but to have to setup at first a transfer the size of the FIFO, and
> > then when it's (or starts to be) depleted, fill it up again.
> 
> According to what you said the driver must implement
> "transfer_one_message" instead of "transfer_one"

I'm not sure what makes you think that I said that.

Maxime

-- 
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com

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