[Librem-5-dev] U-Boot support for uSD
andy at warmcat.com
Thu Dec 27 02:17:49 PST 2018
On 27/12/2018 15:09, Andy Green via Librem-5-dev wrote:
> Hi -
> It seems my reasonably midrange for 2018 uSD (Sandisk Ultra U1 32GB)
> cannot be brought up by U-Boot on the dev board.
> u-boot=> mmc dev 1
> Card did not respond to voltage select!
> mmc_init: -95, time 29
> But there's no evident problem using that card on a Linux box via a
> cheapo USB adapter.
> "Just me"? Known issue not on the list of known issues? Any
> recommended cards that do work?
I retried using an ancient Class 10 non-U1 device and then with no
device in... all the same.
Digging around in the schematics  it looks like mmc1 is actually the
sdio connection to the WLAN module. Linux says this:
[ 0.486566] mmc1: SDHCI controller on 30b50000.usdhc [30b50000.usdhc]
[ 0.514651] mmc1: new high speed SDIO card at address fffd
The actual uSD is connected via an MA8627  which is a USB hub + mmc /
sd adapter. The hub part appears in Linux as
Bus 001 Device 002: ID 14cd:8601 Super Top
However the other two logical devices seem to be spoken for, the WAN
module and the interface to the SIM card it seems.
Bus 001 Device 005: ID 1e0e:9001 Qualcomm / Option
Bus 001 Device 004: ID 0424:1104 Standard Microsystems Corp.
If you stick a uSD card in though, there dynamically appears also
Bus 001 Device 005: ID 14cd:8170 Super Top
which is the mass storage device connection to the uSD card. And
/dev/sda* appears in Linux.
Back in U-Boot, armed with this new knowledge: no joy
u-boot=> usb start
No controllers found
I intended to put a newly-built kernel on uSD and have U-Boot boot from
it to test it, but it's not supported until U-Boot supports the USB
controller so it seems.  discusses various update scenarios (mainly
whole-image) but not this kind of thing.
I'll try putting my kernel pieces on eMMC with different names and have
U-Boot boot from there by hand to get the same effect.
More information about the Librem-5-dev