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

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Message-ID: <8159c3a5-af74-9f13-aedb-7ecc708bdff6@orpaltech.com>
Date:   Thu, 5 Apr 2018 16:44:16 +0300
From:   Sergey Suloev <ssuloev@...altech.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     Maxime Ripard <maxime.ripard@...tlin.com>,
        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 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.