[U-Boot] iMX6 IPU configuration by EDID

[U-Boot] iMX6 IPU configuration by EDID

[Luca Ellero]

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.

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?

Thanks
Regards
Luca


-- 
Luca Ellero

E-mail: luca.ellero at brickedbrain.com
Internet: www.brickedbrain.com

[U-Boot] iMX6 IPU configuration by EDID

[Eric Nelson]

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

[U-Boot] iMX6 IPU configuration by EDID

[Luca Ellero]

On 17/03/2015 15:25, Eric Nelson wrote:
> 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.
>

Hi Eric,
thank you for your reply.
I'll try to investigate the Linux driver then.
Kind regards
Luca


-- 
Luca Ellero

E-mail: luca.ellero at brickedbrain.com
Internet: www.brickedbrain.com