Raspberry Pi Compute Module

[Martin Sperl]

> On 27.08.2015, at 17:13, Stephen Warren <swarren at wwwdotorg.org> wrote:
> 
>> On 08/26/2015 07:57 AM, Martin Sperl wrote:
>> 
>>> On 24.07.2015, at 05:58, Stephen Warren <swarren at wwwdotorg.org> wrote:
>>> 
>>> On 07/22/2015 10:58 AM, Stefan Wahren wrote:
>>>> Hi Stephen,
>>>> 
>>>>> Am 22.07.2015 um 05:41 schrieb Stephen Warren:
>>>>>> On 07/17/2015 11:08 AM, Stefan Wahren wrote:
>>>>>> Hi all,
>>>>>> 
>>>>>> is there anyone working on Mainline support for the Compute Module?
>>>>>> 
>>>>>> I noticed the downstream kernel already has a bcm2708-rpi-cm.dtsi
>>>>> 
>>>>> It is probably close enough that you can simply use bcm2835-rpi-b.dtb
>>>>> for the CM too, for testing at least.
>>>>> 
>>>>> I just tried this with latest U-Boot and a 4.2.0-rc3 kernel. The eMMC
>>>>> works fine in U-Boot, but the kernel can't access it for some reason,
>>>>> failing with e.g.:
>>>>> 
>>>>> [    3.110503] Waiting for root device /dev/mmcblk0p2...
>>>>> [    3.123895] mmc0: MAN_BKOPS_EN bit is not set
>>>>> [    3.132264] mmc0: error -110 whilst initialising MMC card
>>>>> [    3.788447] cfg80211: Calling CRDA to update world regulatory domain
>>>>> [    4.204078] mmc0: MAN_BKOPS_EN bit is not set
>>>>> [    4.212748] mmc0: error -110 whilst initialising MMC card
>>>>> [    5.283981] mmc0: MAN_BKOPS_EN bit is not set
>>>>> [    5.292657] mmc0: error -110 whilst initialising MMC card
>>>>> 
> 
> This is the case I'm in; I have nothing plugged into the micro USB socket so the value of GPIO47 should be irrelevant. Besides, the eMMC works fine in U-Boot just not in the upstream kernel. Most likely is something to do with low-speed MMC signalling modes working fine (which no doubt U-Boot uses) but the kernel probably tries to switch to some more advanced mode which doesn't work for some reason.
> 
See my second email with the details of mmc debug enabled and loaded via a module -  seems as if sdCMD6 does not work as expected at 400khz...

Unfortunately it is hard to attach a logic analyzer to the eMMC on the back side of the compute module - I guess it would help...