topic Re: Enabling UHSI on USDHC4 in i.MX Processors

Enabling UHSI on USDHC4

jtobias — Sat, 03 Aug 2013 03:41:46 GMT

Hello,

I have a wifi module (Marvel 8797 - SDIO 3.0) that is connected to USDHC4.

My pinmux settings for my port as follow: (LVE is enabled).

CLK 0x4170b9

CMD 0x4170b9

DAT0 0x4170b9

DAT1 0x4170b9

DAT2 0x4170b9

DAT3 0x4170b9

My wifi module works on 1-bit mode but not on 4-bit mode. That is because the SDIO 3.0 require an UHSI (it require 1.8v signaling) enabled and by default, the kernel seems not configured for the said mode.

I would like to know what are the missing keys in order to enable it correctly?.

Regards,

john

Re: Enabling UHSI on USDHC4

jtobias — Sun, 04 Aug 2013 18:39:26 GMT

It looks like I need the SD4_VSELECT signal in order to enable the 1.8v signaling...

Re: Enabling UHSI on USDHC4

jtobias — Mon, 05 Aug 2013 04:24:46 GMT

Hello,

Follow up to my previous post. In freescale linux kernel 3.5.7 alpha release, the device tree for iMX6q-sabresd, the USDHC3 pinctrl settings has SD3_VSELECT. Can anyone could give me some information what exactly the purpose of the said pin?. Is that pin is being use for voltage signaling for UHS-I?.

Regards,

john

Re: Enabling UHSI on USDHC4

DongAisheng — Fri, 30 Aug 2013 06:21:06 GMT

Yes.
VSELECT is an output signal used to change the voltage of the external power supplier.

See bit definition in imx6q/dl spec:

For details you can refer to imx6q/dl reference mannual.

BTW, imx6q sabresd does not have a external control circuit on board to switch signal voltage between 1.8v and 3.3v.
That means imx6q sabresd does not support working on 1.8v mode, as a result, not support SDIO3.0 too.

If you want to try SDIO3.0 you can use imx6q/dl sabreauto board which has that external voltage control circuit on board or imx6sl evk.

Regards

Dong Aisheng

Re: Enabling UHSI on USDHC4

sonugoyal — Thu, 05 Sep 2013 14:40:21 GMT

Hi Dong,

In i.MX6SL there are 2 power domains for GPIO. These are NVCC33_IO and NVCC18_IO. And there is no dedicated pin for SD interface. So which domain is supposed to be controlled by VSELECT bit/pin? Is it for controlling the power supply for SD cards to support different type of cards. And I am assuming that the IO voltage for SDIO interface pads will be automatically taken care by i.MX6SL based on VSELECT bit.

Is my understanding correct?

Regards,

Vinod