[U-Boot] Nokia N900 - eMMC not working after commit 02f3029f1810b99869254d0cf0a71946a008a728

[Lei Wen]

Hi Macpaul,

On Mon, Nov 14, 2011 at 2:36 PM, Macpaul Lin <macpaul at gmail.com> wrote:
> Hi Lei Wen,
>
> 2011/11/14 Lei Wen <adrian.wenl at gmail.com>:
>> Hi Macpaul,
>>
>> I see...
>> It seems some socs always treat cmd8 as failed...?
>> I think it is reasonable to add a quirk configuration surround the judgement
>> of cmd8 execution, so that even it is failed anyway, it could still go on with
>> the following cmd sequence. If this quirk is not defined, and return behavior
>> is still kept.
>>
>> What do you think for this?
>>
>> Thanks,
>> Lei
>>
>
> I've not check this with the SD phy specification.
> The command process should be backward compatible between 3.0 and 1.0.
>
> Could you please provide this more detail with the specification?
> For example, could you please provide what section in the specification
> and how the state machine in MMC card should be operated.
> Then we can check it more detail and see if the solution is reasonable.

The 74 clock requirement is mentioned in both sd[1] and mmc spec[2].
[1] page 91, section 6.4.1 power up, SD specification, part 1,
Physical layer Simplificated Specification, version 2.0
[2] page 54, section 7.3.1 Card reset to pre-idle state, JESD84-A44

>
> Moreover, if you could provide where the Linux code is related to the problem
> and how dose Linux deal with this problem will be good, also.

For linux, it would direcly clear the HIGH SPEED flag for following
mmc_send_app_op_cond().
Linux v3.2-rc1: drivers/mmc/core/sd.c: line 712

>
> As you said in patch, "some card strictly obey the 74 clocks rule",
> could you provide the information of the card that you're using?

The card we met trouble on is SanDisk 8GB class4 sd card.

>
> Add #ifdef to the code is a quick solution, but I think the we need to
> figure out if there is other method
> to help on 74 clock adoptable on more general case.
>
> --
> Best regards,
> Macpaul Lin
>

Best regards,
Lei