Re: [PATCH] mmc: sunxi: fix unusuable eMMC on some H6 boards by disabling DDR

From: Linus Walleij
Date: Wed Aug 28 2019 - 08:52:46 EST

On Sun, Aug 25, 2019 at 5:06 PM Alejandro GonzÃlez
<alejandro.gonzalez.correo@xxxxxxxxx> wrote:

> Jernej Skrabec compared the BSP driver with this
> driver, and found that the BSP driver configures pinctrl to operate at
> 1.8 V when entering DDR mode (although 3.3 V operation is supported), while
> the mainline kernel lacks any mechanism to switch voltages dynamically.
> the kernel lacks the required
> dynamic pinctrl control for now

This is not a pin control thing, the I/O voltage level is usually
controlled by a regulator called VCCQ, if the selection of the
voltage rails is inside the pin control registers, see the solution
in drivers/pinctrl/sh-pfc/pfc-sh73a0.c where we simply provide
a regulator from inside the pinctrl driver to make things easy
for the MMC core. Do this thing!

If you don't have time to fix it up properly right now I would slap
in a big FIXME in the code so people know this needs
to be fixed properly.

Linus Walleij