linux-kernel - Re: [BUG] SPI broken for SPI based panel drivers

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Message-ID: <CAGngYiXWKgu+RKvbUWCSy2pDktc8Uj6+PtWi0oc8tAgiDgoUFw@mail.gmail.com>
Date:   Fri, 4 Dec 2020 14:19:11 -0500
From:   Sven Van Asbroeck <thesven73@...il.com>
To:     "H. Nikolaus Schaller" <hns@...delico.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Lukas Wunner <lukas@...ner.de>,
        Mark Brown <broonie@...nel.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Discussions about the Letux Kernel 
        <letux-kernel@...nphoenux.org>,
        Andreas Kemnade <andreas@...nade.info>
Subject: Re: [BUG] SPI broken for SPI based panel drivers

On Fri, Dec 4, 2020 at 11:52 AM H. Nikolaus Schaller <hns@...delico.com> wrote:
>
> >> Anyways it is debatable if this is a bug at all. It is just a definition.
> >
> > I respectfully disagree. Prior to the fix, your panel's active-low chip select
> > needed to be described in the devicetree with 'spi-cs-high'. That sounds
> > very much like a bug to me.
>
> It could have been described by ACTIVE_LOW without spi-cs-high but that did
> emit a nasty and not helpful warning on each boot.

That will not work, try it out. You will see that without the bugfix, your chip
select is consistently inverted, no matter how you formulate it in the
devicetree.

>
> I'd prefer if you or maybe Linus could submit such a patch and I am happy to review it.

I cannot help you with that, I'm sorry.