Hi, i'm wanting to take advantage of my SD card that's rated for 180MB/s read from Samsung by manually setting it to DDR 200MHz, and wondering how can i achieve that.
I see the card is recognized by default as the UHS-I speed of SDR104 and runs at 192MHz SDR 4bit by default, but those SD cards are supposedly HS400 eMMC inside capable of 200MHz DDR 4bit (which is how vendors such as Samsung, SanDisk etc. to achieve beyond-UHS-I speed without UHS-II).
Is there a way to force the host/SoC to use that clock, instead of the UHS-I one? Below are the default specs i'm seeing.
root@GL-AXT1800:~# dmesg | tail -2
[100825.724529] mmc0: new ultra high speed SDR104 SDXC card at address 59b4
[100825.735035] mmcblk0: mmc0:59b4 EF8S5 478 GiB
root@GL-AXT1800:~# head /sys/kernel/debug/mmc0/*
==> /sys/kernel/debug/mmc0/clock <==
192000000
==> /sys/kernel/debug/mmc0/ios <==
clock: 192000000 Hz
actual clock: 192000000 Hz
vdd: 18 (3.0 ~ 3.1 V)
bus mode: 2 (push-pull)
chip select: 0 (don't care)
power mode: 2 (on)
bus width: 2 (4 bits)
timing spec: 6 (sd uhs SDR104)
signal voltage: 0 (1.80 V)
driver type: 0 (driver type B)