linux-kernel - Re: [PATCH 3/5] spi: dw-mmio: add MSCC Ocelot support

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Message-ID: <20180717214024.GD3211@piout.net>
Date:   Tue, 17 Jul 2018 23:40:24 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Mark Brown <broonie@...nel.org>, James Hogan <jhogan@...nel.org>,
        Paul Burton <paul.burton@...s.com>,
        linux-spi <linux-spi@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux MIPS Mailing List <linux-mips@...ux-mips.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Allan Nielsen <allan.nielsen@...rosemi.com>,
        Rob Herring <robh+dt@...nel.org>
Subject: Re: [PATCH 3/5] spi: dw-mmio: add MSCC Ocelot support

On 18/07/2018 00:34:37+0300, Andy Shevchenko wrote:
> On Tue, Jul 17, 2018 at 5:23 PM, Alexandre Belloni
> <alexandre.belloni@...tlin.com> wrote:
> > Because the SPI controller deasserts the chip select when the TX fifo is
> > empty (which may happen in the middle of a transfer), the CS should be
> > handled by linux. Unfortunately, some or all of the first four chip
> > selects are not muxable as GPIOs, depending on the SoC.
> >
> > There is a way to bitbang those pins by using the SPI boot controller so
> > use it to set the chip selects.
> >
> > At init time, it is also necessary to give control of the SPI interface to
> > the Designware IP.
> 
> > +       ret = dw_spi_mscc_init(pdev, dwsmmio);
> > +       if (ret)
> > +               goto out;
> 
> > +       { .compatible = "mscc,ocelot-spi", .data = dw_spi_mscc_init},
> 
> Looks like you were thinking about something like
> 
> init_func = device_get_match_data(...);
> if (init_func) {
>  ret = init_func();
>  if (ret)
>    return ret;
> }
> 
> ?
> 

Ah sure, I forgot to do that after testing.

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