[U-Boot] [PATCH 1/4] mmc: fsl_esdhc: introduce vs18_enable for 1.8V fix I/O

[Peng Fan]

Hi York,

> -----Original Message-----
> From: York Sun [mailto:york.sun at nxp.com]
> Sent: Thursday, April 20, 2017 11:22 AM
> To: Peng Fan <peng.fan at nxp.com>; sbabic at denx.de;
> jh80.chung at samsung.com
> Cc: otavio at ossystems.com.br; u-boot at lists.denx.de
> Subject: Re: [PATCH 1/4] mmc: fsl_esdhc: introduce vs18_enable for 1.8V fix
> I/O
> 
> On 04/19/2017 07:46 PM, Peng Fan wrote:
> > When using eMMC with 1.8V I/O, the VSELECT bit need to be set in the
> > USDHC controller when init.
> >
> > This patch adds a parameter "vs18_enable" in fsl_esdhc_cfg structure
> > and priv data, so each controller can have different settings.
> >
> > We could not use CONFIG_SYS_FSL_ESDHC_FORCE_VSELECT, it has problem
> > that it will apply to all USDHC controllers and it only set the 1.8V
> > at init phase. So if user does not select to the eMMC device, the
> > voltage on the I/O pins are not correct.
> >
> 
> Peng,
> 
> I don't quite understand this. Isn't the voltage supplied by the board?
> I believe we have detection on our boards to decide 3.3v or 1.8v should be
> supplied. Does that have anything to do with the voltage you are talking about?
> I am referring to LS1046ARDB.

From i.MX6 RM, the VSELECT bit,
Voltage Selection
Change the value of output signal VSELECT, to control the voltage on pads for external card. There must
be a control circuit out of uSDHC to change the voltage on pads.
1 Change the voltage to low voltage range, around 1.8 V
0 Change the voltage to high voltage range, around 3.0 V

If the emmc vqmmc supply is 1.8V, the vselect must be set to 1.
I am not sure if this is the case for LS family.

Thanks,
Peng.

> 
> York