Enable HS400 in Foresee eMMC?


First of all congratulations to the Radxa team for this awesome little board.

I have a 4GB/32GB Zero with the Radxa Debian installed.

I’m using it as a daily driver for programming and browsing and it works perfectly… A less than 5 watt fully working PC! :open_mouth:

I see in the emmc docs that it can reach a max read speed of 200MB/s. Testing the read speed with hdparm only reaches 131MB/s.

The Foresee 32GB emmc supports HS400 but it seems that it is not enabled by Debian.

Here is what I found in dmesg:

rock@radxa-zero:~$ dmesg | grep mmc
[    3.141608] meson-gx-mmc ffe05000.sd: Got CD GPIO
[    3.461728] meson-gx-mmc ffe03000.sd: allocated mmc-pwrseq
[    3.476567] meson-gx-mmc ffe07000.mmc: allocated mmc-pwrseq
[    3.542928] mmc2: queuing unknown CIS tuple 0x80 (2 bytes)
[    3.545073] mmc2: queuing unknown CIS tuple 0x80 (3 bytes)
[    3.551489] mmc2: queuing unknown CIS tuple 0x80 (3 bytes)
[    3.558599] mmc2: queuing unknown CIS tuple 0x80 (7 bytes)
[    3.565868] mmc2: queuing unknown CIS tuple 0x81 (9 bytes)
[    3.639199] mmc2: new ultra high speed SDR50 SDIO card at address 0001
[    3.642926] mmc0: new **HS200 MMC** card at address 0001
[    3.652493] mmcblk0: mmc0:0001 SLD32G 28.9 GiB 
[    3.656531] mmcblk0boot0: mmc0:0001 SLD32G partition 1 4.00 MiB
[    3.662371] mmcblk0boot1: mmc0:0001 SLD32G partition 2 4.00 MiB
[    3.667986] mmcblk0rpmb: mmc0:0001 SLD32G partition 3 4.00 MiB, chardev (242:0)
[    3.702215]  mmcblk0: p1 p2
[    4.006031] EXT4-fs (mmcblk0p2): mounted filesystem with ordered data mode. Opts: (null)
[    4.908317] EXT4-fs (mmcblk0p2): re-mounted. Opts: discard
[    6.529007] brcmfmac mmc2:0001:1: Direct firmware load for brcm/brcmfmac43456-sdio.radxa,zero.txt failed with error -2

Is HS400 really disabled? If it is so, what should I do to enable HS400?

Thank you! :slightly_smiling_face:

Foresee’s eMMC was known to have issue with HS400. We have sent some samples to a Manjaro developer who is working on fixing this issue.

Hi RadxaYuntian,

Any news on this issue?

Is it possible to enable HS400 on the Foresee eMMC?

Thanks! :slightly_smiling_face:

@spikerguy What did you guys learned about those Foresee eMMC we sent to you?


As one can read in the Foresee SLG32D eMMC datasheet (see below), enabling HS400 would effectively double the max speed of our Zero eMMC, from (near) 200MB/s to (near) 400MB/s.

This is a dramatic speed up for this tiny but amazing board.

I think it is well worth looking into.

Is there any Linux hacker out there that knows how to set the eMMC to HS400?

You can find a link to the datasheet below.

Thanx! :slightly_smiling_face:


Anyone was able to enable HS400?