[U-Boot] Sunxi (Allwinner A20) GPIO problems on u-boot 2016.1 and 2016.3-rc3 but not on 2015.10

[Hans de Goede]

Hi,

On 03-03-16 17:54, Hendrik wrote:
> Hello Hans,
>
> Thank you very much for your message. The PIO program reported 'PE6<0><0><1><1>' for both U-Boots but changing the configuration's CONFIG_AXP_ALDO3_VOLT and CONFIG_AXP_ALDO4_VOLT back to 2800 did indeed solve the problem. I can run U-Boot 2016.01 now and control PE6 properly.
>
> LDO3 is connected to pin F19 in the Olimex schematics (VCC_CSI0, in the A20 datasheet mentioned as Port E Power Supply) and LDO4 is connected to pin E18 (VCC_CSI1 mentioned as Port G Power Supply).
>
> So would the change in u-boot make sense by setting the default to 0 now? I'm not sure if the git remark 'LDO3 and LDO4 are normally either unused, or used to power csi attached camera sensors' is correct as it seems (also?) to be the source or reference for the A20 chip pins itself..? At least this is the case for multiple (all?) Olimex A10/A20 boards (I checked A20-SOM, A20-LIME2, A20-Lime and A10-Lime).

The using of ldo3/4 for pins which are on a general header seems to be an olimex board thing, I've checked a few non olimex schematics:

-cubieboard: has E18 / E19 connected to VCC-3V3
-cubietruck: has E18 / E19 connected to VCC-3V3
-bananapi: has E18 connected to VCC-3V3, E19 to VCC-CSI which seems to come from the camera connector
-orangepi: has E18 / VCC-PE connected to VCC-3V3, E19 to VCC-CSI0 which comes from a dedicated LDO, not one the axp ldo-s
-orangepi-mini: has E18 / VCC-PE connected to VCC-3V3, E19 to VCC-CSI0 which comes from a dedicated LDO, not one the axp ldo-s

Also note that even if you enable LDO3 and LDO4 in the boot-loader,
the kernel will go and turn them off as soon as it is done booting,
the fact that it doesn't for you means that you probably do not
have the dts bits for the kernel to properly control the
axp209 regulators yet, as soon as you add this ldo3 and ldo4
will get turned off after kernel boot, unless you spcecificaly
declare them as always-on in the dts.

With that said, I will happily accept u-boot patches to
enable LDO3 / LDO4 for Olimex boards where the PE / PF
pins are connected to a general purpose header.

Regards,

Hans