Re: [PATCH] media: arch: sh: migor: Fix TW9910 PDN gpio

[jacopo mondi <jacopo@jmondi.org>]

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Hi Laurent,

On Wed, May 30, 2018 at 03:38:01PM +0300, Laurent Pinchart wrote:
> Hi Jacopo,
>
> On Wednesday, 30 May 2018 15:23:43 EEST jacopo mondi wrote:
> > On Wed, May 30, 2018 at 02:52:31PM +0300, Laurent Pinchart wrote:
> > > On Wednesday, 30 May 2018 12:30:49 EEST Geert Uytterhoeven wrote:
> > >> On Wed, May 30, 2018 at 11:13 AM, Jacopo Mondi wrote:
> > >>> The TW9910 PDN gpio (power down) is listed as active high in the chip
> > >>> manual. It turns out it is actually active low as when set to physical
> > >>> level 0 it actually turns the video decoder power off.
> > >>
> > >> So the picture "Typical TW9910 External Circuitry" in the datasheet,
> > >> which ties PDN to GND permanently, is wrong?
> >
> > Also the definition of PDN pin in TW9910 manual, as reported by Laurent made
> > me think the pin had to stay in logical state 1 to have the chip powered
> > down. That's why my initial 'ACTIVE_HIGH' flag. The chip was not
> > recognized, but I thought it was a local problem of the Migo-R board I
> > was using.
> >
> > Then one day I tried inverting the pin active state just to be sure,
> > and it started being fully operational :/
> >
> > > The SH PTT2 line is connected directory to the TW9910 PDN signal, without
> > > any inverter on the board. The PDN signal is clearly documented as
> > > active-high in the TW9910 datasheet. Something is thus weird.
> >
> > I suspect the 'active high' definition in datasheet is different from
> > our understanding. Their 'active' means the chip is operational, which
> > is not what one would expect from a powerdown pin.
> >
> > > Jacopo, is it possible to measure the PDN signal on the board as close as
> > > possible to the TW9910 to see if it works as expected ?
> >
> > Not for me. The board is in Japan and my multimeter doesn't have cables
> > that long, unfortunately.
>
> How about trying that during your next trip to Japan ? :-)

Ok, I'll stop looking for cables 10.000km long on amazon.
>
> --
> Regards,
>
> Laurent Pinchart
>
>
>

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