[U-Boot] iMX6 IPU configuration by EDID

[Eric Nelson <eric.nelson@boundarydevices.com>]

Hi Luca,

On 03/17/2015 03:04 AM, Luca Ellero wrote:
> Hi all,
>
> I'm trying to configure IPU on a iMX6 based platform by reading EDID
> from the external monitor.
> 
> Everything seem to work fine except for the pixelclock. In particular my
> monitor has a standard resolution of 1280x1024 at 60 (108 MHz pixelclock).
> 
> When the function ipu_init_sync_panel (file ipu_disp.c) is called it
> correctly receive 108 MHz as pixelclock. but during the execution of
> this function it gets rounded to 130 MHz.
> 
> I can see that the function calls clk_round_rate to round the clock to
> 130 MHz but it's not clear for me how it works.
> 

It's been a while since I've looked at this, but I believe there's
a hidden fixed clock somewhere in the IPU driver.

	http://lists.denx.de/pipermail/u-boot/2014-January/thread.html#170363

> Can someone please tell me how to get the exact pixelclock I would like
> to achieve? I've carefully read the iMX6 manual but it's not very useful
> in this case.
>
> Another doubt that I have regards the field "ext_clk" of parameter
> "ipu_di_signal_cfg_t sig". In this case, is it better to set it or not?
> 

I believe this is supposed to be set for HDMI, such that the IPU
clock is derived from the HDMI PHY clock and it's best to use
the Linux driver as a guide.

Regards,


Eric