Edit: after dumping default register config from PMIC under U-Boot, seems eMMC’s power rail already set to 1.8v by default. So the speed issue is becoming more intreresting…
Edit 2: Whatever I change device tree config to, none of them could get a faster read speed than 20M/s… Even kernel reports a MMC clock over 90Mhz
For sd card, it’s power rail is shared between multiple devices due to PMIC on board lacks rails and is set to 3.3V, causing it cannot reach higher speed mode which uses 1.8V mode.
However on-board emmc slot has a dedicated power rail from PMIC, so it’s possible to make it reach maximum speed mode, but current PMIC driver doesn’t support that.
To solve this problem,I’m working on a new driver which could be upstreamed: GitHub - Headcrabed/linux at axp15060
This driver currently lacks GPIO support, and not tested yet. But I’m busy these days to finish this driver…