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

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Message-ID: <CAGngYiUG76Q-cb_HdDKMia5yXzv_mS+5NPeaBquK3_4b3tr-4Q@mail.gmail.com>
Date:   Tue, 1 Dec 2020 11:10:49 -0500
From:   Sven Van Asbroeck <thesven73@...il.com>
To:     "H. Nikolaus Schaller" <hns@...delico.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        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>
Subject: Re: [BUG] SPI broken for SPI based panel drivers

Nikolaus,

On Tue, Dec 1, 2020 at 9:38 AM H. Nikolaus Schaller <hns@...delico.com> wrote:
>
> Let's work on a fix for the fix now.
>

Are you quite sure the chip-select of the tpo,td028ttec1 panel
is active-high? A quick google produced a datasheet which
seems to indicate that XCS is active-low?

See page 17 here:
http://www.lcd-source.com/datasheet/TPO/TD028TTEC1.pdf

It is of course possible that you are driving that line behind
some inverting circuitry. Hardware designers seem to do that
all the time, if they need to go from one voltage domain to
the other, etc.