[U-Boot] [bug report] sunxi: booting from eMMC

[Hans de Goede]

HI,

On 19-09-16 15:17, Maxime Ripard wrote:
> On Wed, Sep 14, 2016 at 12:05:19PM +0200, Hans de Goede wrote:
>> Hi,
>>
>> On 13-09-16 13:50, Maxime Ripard wrote:
>>> Hi,
>>>
>>> On Mon, Sep 12, 2016 at 04:47:49PM +0200, Hans de Goede wrote:
>>>> On 12-09-16 15:56, Maxime Ripard wrote:
>>>>> Hi,
>>>>>
>>>>> On Mon, Sep 12, 2016 at 01:53:24PM +0200, Ciprian Manea wrote:
>>>>>> I'm using a SinA33 dev board (Allwinner a33 SoC) and at the moment
>>>>>> I'm trying to boot from the eMMC.
>>>>>>
>>>>>> But it fails in the following way:
>>>>>>
>>>>>>
>>>>>> *Got the following error at boot time:*
>>>>>> *U-Boot SPL 2016.09-rc2-00125-g6e8b42f (Sep 08 2016 - 11:00:46) DRAM: 1024
>>>>>> MiB Trying to boot from MMC2 MMC Device 1 not found spl: could not find mmc
>>>>>> device. error: -19 SPL: failed to boot from all boot devices ### ERROR ###
>>>>>> Please RESET the board ###*
>>>>>
>>>>> So I've been on the same issue for the last couple of days.
>>>>>
>>>>> Since that board is already supported, adding support for the eMMC
>>>>> basically came down to that patch on top of 2016.09-rc2.
>>>>>
>>>>> http://code.bulix.org/kcgxri-106037?raw
>>>>>
>>>>> (Quite hackish, the 8-Bits part being a separate issue that would need
>>>>> to be addressed somehow).
>>>>>
>>>>> However, it doesn't work, neither when flashing u-boot on the eMMC
>>>>> itself (where there's a timeout error in the SPL) nor when trying to
>>>>> access the eMMC from a U-Boot loaded from the (external) SD.
>>>>>
>>>>> In the latter case, even mmc dev 1 fails silently.
>>>>>
>>>>> I traced that down to the mmc_switch here:
>>>>> http://git.denx.de/?p=u-boot.git;a=blob;f=drivers/mmc/mmc.c#l530
>>>>>
>>>>> Which fails with ETIMEDOUT, and more specifically, it's the call to
>>>>> mmc_rint_wait here
>>>>> http://git.denx.de/?p=u-boot.git;a=blob;f=drivers/mmc/sunxi_mmc.c#l383
>>>>> that times out.
>>>>>
>>>>> Increasing the timeout value (to 10000) doesn't really change
>>>>> anything. I guess this is also the reason why we had a timeout error
>>>>> in the SPL.
>>>>>
>>>>> This eMMC works fine in Linux, with the same muxing (and I guess the
>>>>> earlier commands wouldn't be successful if the muxing or power was not
>>>>> set up appropriately). So I'm kind of running out of ideas on what
>>>>> could be the root cause of this.
>>>>>
>>>>> Hans, any ideas?
>>>>
>>>> Maybe the emmc needs external pull-ups ? I don't remember if u-boot
>>>> always enables those or not ...
>>>
>>> So I pushed this a bit more, and it seems like commenting the call to
>>> mmc_change_freq makes everything just work.
>>>
>>> Reading the JEDEC spec, it looks like when you switch to high speed,
>>> you also need to change the controller clock rate, that u-boot doesn't
>>> seem to do at the moment, which obviously will fail, since the
>>> controller will be stuck at the former rate, while the eMMC would be
>>> switched.
>>>
>>> If I comment mmc_change_freq, everything works.
>>
>> Hmm, I'm pretty sure the u-boot sunxi mmc code
>> does properly change the clock, see mmc_set_mod_clk() in
>> drivers/mmc/sunxi_mmc.c
>>
>> This will switch to the right PLL, etc. So there likely is
>> something else going on making things not work at higher
>> speeds.
>
> Yep, I noticed that. However, what confuses me more is that the
> command seems to be sent here:
> http://git.denx.de/?p=u-boot.git;a=blob;f=drivers/mmc/mmc.c#l530
>
> And set_ios is being called after we check that everything
> works. Linux for example calls set_ios right after switching
> http://lxr.free-electrons.com/source/drivers/mmc/core/mmc.c#L965
>
>> Maybe we need a higher driver strenghts at the mmc io pins, or maybe
>> we've a completely unrelated issue ?
>
> I've tested that already. It doesn't change the outcome.
>
>> I'm pretty sure that the eMMC's on A20 devices work fine in 50MHZ
>> (SDR) mode.
>
> What emmc was that? Did it support HS? Was it considered an SD (and
> went through sd_change_freq), or an MMC?

Here is what "mmc info" in u-boot says on my UTOO P66 tablet (A13)
with 4G eMMC (manually transcribed, no serial console):

Device: SUNXI SD/MMC
Manufacturer ID: 70
OEM: 100
Name: MMC04
Tran Speed: 52000000
Rd Block Len: 512
MMC version 4.4.1
High Capacity: Yes
Bus-width: 4-bit
<bunch of sizes>

And here is /sys/kernel/debug/mmc1/ios under linux:

clock:          52000000 Hz
vdd:            21 (3.3 ~ 3.4 V)
bus mode:       2 (push-pull)
chip select:    0 (don't care)
power mode:     2 (on)
bus width:      3 (8 bits)
timing spec:    1 (mmc high-speed)
signal voltage: 0 (3.30 V)
driver type:    0 (driver type B)

HTH,

Regards,

Hans