Re: [PATCH v5 4/5] media: ov5640: add support of DVP parallel interface

[Maxime Ripard <maxime.ripard-LDxbnhwyfcJBDgjK7y7TUQ@public.gmane.org>]

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On Mon, Feb 05, 2018 at 11:42:11AM +0000, Fabrizio Castro wrote:
> Hello Maxime,
> 
> thank you for your feedback.
> 
> > > > +/*
> > > > + * configure parallel port control lines polarity
> > > > + *
> > > > + * POLARITY CTRL0
> > > > + * - [5]:PCLK polarity (0: active low, 1: active high)
> > > > + * - [1]:HREF polarity (0: active low, 1: active high)
> > > > + * - [0]:VSYNC polarity (mismatch here between
> > > > + *datasheet and hardware, 0 is active high
> > > > + *and 1 is active low...)
> > >
> > > I know that yourself and Maxime have both confirmed that VSYNC
> > > polarity is inverted, but I am looking at HSYNC and VSYNC with a
> > > logic analyser and I am dumping the values written to
> > > OV5640_REG_POLARITY_CTRL00 and to me it looks like that HSYNC is
> > > active HIGH when hsync_pol == 0, and VSYNC is active HIGH when
> > > vsync_pol == 1.
> >
> > Which mode are you testing this on?
> 
> My testing environment is made of the sensor connected to a SoC with
> 8 data lines, vsync, hsync, and pclk, and of course I am specifying
> hsync-active, vsync-active, and pclk-sample in the device tree on
> both ends so that they configure themselves accordingly to work in
> DVP mode (V4L2_MBUS_PARALLEL), with the correct polarities.
>
> Between the sensor and the SoC there is a noninverting bus
> transceiver (voltage translator), for my experiments I have plugged
> myself onto the outputs of this transceiver only to be compliant
> with the voltage level of my logic analyser.

Sorry, my question was more about the resolution, refresh rate, etc.

> > The non-active periods are insanely high in most modes (1896 for an
> > active horizontal length of 640 in 640x480 for example), especially
> > hsync, and it's really easy to invert the two.
> 
> I am looking at all the data lines, so that I don't confuse the
> non-active periods with the active periods, and with my setup what I
> reported is what I get. I wonder if this difference comes from the
> sensor revision at all? Unfortunately I can only test the one camera
> I have got.

I don't really know then. I've had issues with the polarities on my
side, but it was on the receiver side and the sensor part looked like
what is documented.

Maxime

-- 
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
http://bootlin.com

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