Re: [PATCH] ARM: dts: sun7i: Add Goodix GT911 nodes for Wexler TAB7200

[Maxime Ripard <maxime.ripard-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>]

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On Sat, Apr 11, 2015 at 07:18:16PM +0300, Aleksei Mamlin wrote:
> On Thu, 2 Apr 2015 11:22:59 +0200
> Maxime Ripard <maxime.ripard-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org> wrote:
> 
> > On Tue, Mar 31, 2015 at 10:14:20PM +0300, Aleksei Mamlin wrote:
> > > On Tue, 31 Mar 2015 07:43:38 -0700
> > > Maxime Ripard <maxime.ripard-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org> wrote:
> > > 
> > > > Hi,
> > > > 
> > > > On Tue, Mar 31, 2015 at 11:18:17AM +0300, Aleksei Mamlin wrote:
> > > > > This patch adds nodes for the Goodix GT911 touchscreen controller found
> > > > > on the Wexler TAB7200 tablet. Controller uses one of following I2C
> > > > > addresses: 0x5d or 0x14, so just add two nodes.
> > > > 
> > > > In which case are these different addresses encountered? Different
> > > > revisions of the same board?
> > >
> > > According to the datasheet it is a feature of the controller. 
> > > The address(0x5d or 0x14) can be configured using a reset sequence,
> > > which has not yet been implemented in the driver.
> > 
> > Which address is set up by the bootloader then?
>
> I assume that bootloader(u-boot) didn't sets up any address, but touchscreen
> controller usually uses 0x5d. Sometimes, after hard reset, it uses 0x14.
> For this we need nodes on both adresses.

I'm confused, who changes that address then?

The controller itself?

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

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