[U-Boot] [PATCH v1 16/16] board: Add Qualcomm Dragonboard 410C support

[Mateusz Kulikowski <mateusz.kulikowski@gmail.com>]

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Hi Simon,

On 13.01.2016 21:32, Simon Glass wrote:
[...]
> On 11 January 2016 at 15:01, Mateusz Kulikowski
> <mateusz.kulikowski@gmail.com> wrote:
[...]

>> &pm8916_gpios {
>>
>>         usb_hub_reset_pm: usb_hub_reset_pm {
>>                 pinconf {
>>                         pins = "gpio3";
>>                         function = PMIC_GPIO_FUNC_NORMAL;
>>                         output-low;
>>                 };
>>         };
>>
>> (https://github.com/torvalds/linux/blob/master/arch/arm64/boot/dts/qcom/apq8016-sbc-pmic-pins.dtsi)
>>
>> I decided to move them away from PMIC, as they only use specific gpios.
>>
>> To be honest they are just a references so I don't have to hardcode gpio names/numbers in
>> board sources.
>>
>> Is it ok if I keep it that way? Could you suggest better approach?
> 
> We should avoid forking the device tree and making up bindings.
> 
> Really it looks like qcom,qpnp-pin should be a pinctrl driver. Then
> pinctrl-0 in your device node will automatically pick up the correct
> function.

I gave it a bit thought played a bit (perhaps small bit) with pinctl, 
did Phone-a-Friend, looked at rockchip @ your tree and:

1. I agree that it's good idea to have the same bindings in U-Boot & Linux.

2. Perhaps in "generic" solution (say for all qcom pmics) it would be nice 
to have possibility to configure some functions of this pins, but all I need 
for now is to change value of 2 gpio pins to 1/0. 

3. Learning/writing "proper" pinctrl driver will take me some time (and probably
few patch versions).

4. In my (very) humble opinion, there are few improvements that I consider more important 
and would like to do first (for example usb device controller or ADMA support for sdhci).
Also Syed would probably like to have support for his Dragonboard 810 that is 
similar (and kind-of blocked by this release).

My proposal is to use mainline Linux entries for hub/switch pins and then do 
addition as in (for example) exynos 4210: 
add dragonboard410c-uboot.dtsi that will have u-boot specific extension.
In this case - gpio handle so I can query gpio the same way I did in the past.

Of course I will upgrade dt bindings documentation.

And in future I will have to master pinmux/pinctrl as I will need it to get 
rid of Little Kernel (and do pin configuration for UART, MMC etc.) - I can then
"upgrade" this code.


Just FYI: I don't plan to abandon board the day it gets to mainline ;)

Regards,
Mateusz

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