On Wed, Aug 28, 2019 at 8:52 PM Linus Walleij <linus.walleij@xxxxxxxxxx> wrote: > > On Sun, Aug 25, 2019 at 5:06 PM Alejandro González > <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. AFAIK The Pine H64 does not have the ability to switch I/O voltages. It is fixed to either 1.8V (the default based on the schematics) or 3.3V. > (...) > > 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! Or if it's simply voltage trimming for input, the a80 pinctrl driver has something similar. Basically it registers a notifier on the voltage rail supplying a set of pins, and toggles the register to match the external voltage provided. Unfortunately the user manual is quite vague on what it actually is. > 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. +1 ChenYu
