linux-kernel - Re: [PATCH] omapdss: Add new panel driver for Topolly td028ttec1 LCD.

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Date:	Fri, 11 Oct 2013 12:04:36 +0300
From:	Tomi Valkeinen <tomi.valkeinen@...com>
To:	Belisko Marek <marek.belisko@...il.com>
CC:	"Dr. H. Nikolaus Schaller" <hns@...delico.com>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Jean-Christophe PLAGNIOL-VILLARD <plagnioj@...osoft.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-omap@...r.kernel.org" <linux-omap@...r.kernel.org>,
	<linux-fbdev@...r.kernel.org>
Subject: Re: [PATCH] omapdss: Add new panel driver for Topolly td028ttec1
 LCD.

On 11/10/13 11:59, Belisko Marek wrote:

>> That's why I won't allow representing this panel as having 4 gpios in
>> the DT data, because that is not correct. The panel has 3 pins. But
>> then, the panel does allow reading, which could be implemented using 4
>> gpios as you have done. This data should be in the spi-bitbang data, and
>> the panel should just use the standard SPI framework.
> I disagree. There are different drivers which pass in platform data
> gpios (encoder-tfp410.c or encoder-tpd12s015.c)
> and those must be covered by DT then. I cannot see problem why to have
> for td028 panel 3 or 4 gpios defined in DT.

Yes, they are plain GPIOs, and defined in the spec for the respective
chip. There's no alternative to how they could be represented.

Here, with the td028, the spec speaks of 3 pins for the serial bus. Not
4. So there cannot be 4 gpios defined in the panel's data, that just
doesn't make sense.

Additionally, what we have here are not "normal" gpios, but pins for a
serial bus, 3-wire SPI. If the panel data specifies the gpios, then it's
not possible to use real SPI hardware with the panel.

 Tomi



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