linux-kernel - Re: [PATCH] spi: spi-sun6i: implement DMA-based transfer mode

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Message-ID: <20201021150348.g2anzbqalhrmypdl@gilmour.lan>
Date:   Wed, 21 Oct 2020 17:03:48 +0200
From:   Maxime Ripard <maxime@...no.tech>
To:     Chen-Yu Tsai <wens@...e.org>
Cc:     Alexander Kochetkov <al.kochet@...il.com>,
        Mark Brown <broonie@...nel.org>, linux-spi@...r.kernel.org,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] spi: spi-sun6i: implement DMA-based transfer mode

On Tue, Oct 20, 2020 at 11:52:34AM +0800, Chen-Yu Tsai wrote:
> On Tue, Oct 20, 2020 at 1:43 AM Alexander Kochetkov <al.kochet@...il.com> wrote:
> >
> >
> >
> > > 19 окт. 2020 г., в 11:21, Maxime Ripard <maxime@...no.tech> написал(а):
> > >
> > > Hi!
> > >
> > > On Thu, Oct 15, 2020 at 06:47:40PM +0300, Alexander Kochetkov wrote:
> > >> DMA-based transfer will be enabled if data length is larger than FIFO size
> > >> (64 bytes for A64). This greatly reduce number of interrupts for
> > >> transferring data.
> > >>
> > >> For smaller data size PIO mode will be used. In PIO mode whole buffer will
> > >> be loaded into FIFO.
> > >>
> > >> If driver failed to request DMA channels then it fallback for PIO mode.
> > >>
> > >> Tested on SOPINE (https://www.pine64.org/sopine/)
> > >>
> > >> Signed-off-by: Alexander Kochetkov <al.kochet@...il.com>
> > >
> > > Thanks for working on this, it's been a bit overdue
> >
> > Hi, Maxime!
> >
> > We did custom A64 based computation module for our product.
> > Do you mean that A64 is obsolete or EOL product?
> > If so, can you recommend active replacement for A64 from Allwinner same price?
> 
> I believe what Maxime meant was that DMA transfer for SPI is a long
> sought-after feature, but no one had finished it.

Yeah, that's what I meant :)

Maxime

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