(01-18-2018, 07:48 AM)z4v4l Wrote:in attempt to educate ,(01-18-2018, 06:08 AM)xalius Wrote: Can you please calm down and just have a look at the schematics for Rock64... the SD-Card interface has a fixed 3.3V supply, so it will only support 3.3V modes, the eMMC has a fixed 1.8V supply, so it will support 3.3V and 1.8V modes (the lower speed modes also work on 1.8V). To support dual voltage modes, you need hardware support for dynamic adjustment of VCC_IO which is not trivial to implement for u-boot and Linux which is why you don't see that configuration a lot on single board computers...VDD to the card should be fixed at 3.3V for UHS-I cards as per the SDA host controller spec.
Quote:1.8 Signaling Enable field of the Host Control 2 registerWhat hardware support do you mean? Isn't it rk3328 SDA host controller compliant controller? Setting that bit should transit I/O into 1.8V (3.6.1, Voltage switch procedure (for UHS-I), part A2, page 177). Why it is not the case on Rock64?
This bit controls voltage regulator for I/O cell. 3.3V is supplied to the card regardless of signalling voltage.
here are a couple clips of the vcc out of the pmic to the tf [sdcard] one is the 3328 the other is the 3399. you should be able to notice that the 808 on the 3399 sends 1.8-3.3v, on the other hand the 805 of the 3328 sends just 3.3v as remarked in the box in the upper right corner.
and then the tf [sdcard] for each
with the 3328 vcc_sd is3.3 and with 3399 vcc_sdio as shown above is 1.8-3.4v
