linux-kernel - Re: (EXT) Re: (EXT) Re: (EXT) Re: [PATCH 2/2] ARM: dts: imx6qdl: tqma6: minor fixes

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Date:   Wed, 26 Aug 2020 12:32:17 +0200
From:   Matthias Schiffer <matthias.schiffer@...tq-group.com>
To:     Fabio Estevam <festevam@...il.com>
Cc:     Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        NXP Linux Team <linux-imx@....com>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: (EXT) Re: (EXT) Re: (EXT) Re: [PATCH 2/2] ARM: dts: imx6qdl:
 tqma6: minor fixes

On Tue, 2020-08-25 at 14:16 -0300, Fabio Estevam wrote:
> On Tue, Aug 25, 2020 at 11:40 AM Matthias Schiffer
> <matthias.schiffer@...tq-group.com> wrote:
> 
> > Makes sense. Does the following logic sound correct?
> > 
> > - If num-cs is set, use that (and add it to the docs)
> 
> I would not add num-cs to the docs. As far as I can see there is no
> imx dts that uses num-cs currently.

But the previous platform data that was removed in 8cdcd8aeee281 ("spi:
imx/fsl-lpspi: Convert to GPIO descriptors") set different values for
different boards. So maybe some DTS should be using num-cs?


> 
> > - If num-cs is unset, use the number of cs-gpios
> > - If num-cs is unset and no cs-gpios are defined, use a driver-
> > provided
> > default
> > 
> > 
> > I'm not sure if 3 is a particularly useful default either, but it
> > seems
> > it was chosen to accommodate boards that previously set this via
> > platform data. All SoCs I've checked (i.MX6Q/DL, i.MX6UL, i.MX7)
> > have 4
> > internal CS pins per ECSPI instance, so maybe the driver should use
> > that as its default instead?
> 
> I think it is time to get rid of i.MX board files. I will try to work
> on this when I have a chance.
> 
> bout using 4 as default chip select number, please also check some
> older SoCs like imx25, imx35, imx51, imx53, etc

Hmm, I just checked i.MX28, and it has only 3 chip selects per
instance.