Subject: [PATCH RFC 27/46] imx-drm: convert to componentised device support

From: [email-masked] (Eric Nelson)
Date: Tue, 07 Jan 2014 08:30:41 -0700

Hi Philipp,

On 01/07/2014 04:29 AM, Philipp Zabel wrote:
> Am Montag, den 06.01.2014, 19:31 -0700 schrieb Eric Nelson:
>> Hi Russell,
>>
>> On 01/06/2014 10:46 AM, Russell King - ARM Linux wrote:
>>> On Mon, Jan 06, 2014 at 06:41:28PM +0100, Philipp Zabel wrote:
>>>> Hi Eric,
>>>>
>>>> Am Freitag, den 03.01.2014, 12:14 -0700 schrieb Eric Nelson:
>>>>> This is an issue we've seen before. The SABRE Lite board has
>>>>> a voltage divider on the HPD pins and some monitors (esp. DVI
>>>>> monitors) either don't drive things high enough to assert HPD or
>>>>> bounce with connect/disconnect.
>>>>
>>>> Yes, I used a DVI monitor.
>>>>
>>>>> We've instrumented our 3.0.35 kernels to use the RX_SENSE bits
>>>>> instead.
>>>>
>>>> Reacting to RX_SENSE0 instead of HPD seems to work.
>>>
>>> However, it's non-compliant, because HPD can be lowered and raised by
>>> the sink when it changes its EDID data (eg, because you're connected
>>> through a switch and the routing has been changed.)
>>>
>>> So, reacting to RX_SENSE0 instead of HPD has to be a work-around enabled
>>> only for those boards which are broken in this regard.
>>>
>>
>> I understand. We'll need to carry some patches for a while though,
>> since there are lots of these boards in the wild.
>
> Could you point me to your changes? Maybe this could be added to
> mainline as a quirk enabled by a device tree property on sabrelite only.
>

We only have them for 3.0.35 at the moment.

Here's the patch to use RXSENSE instead of HPD
	https://github.com/boundarydevices/linux-imx6/commit/c0439e262bb6c23887d96466b2ab7916aa0488d9

A follow-up patch disables the disconnect detection entirely
unless requested:
	https://github.com/boundarydevices/linux-imx6/commit/d9cd79d11ff9f7a7f89cbc94b68757b67cdfe5fc

Regards,

Eric