[linux-sunxi] Re: [PATCH v2 06/18] arm64: dts: allwinner: a64: Orange Pi Win: Add UARTs

[andre.przywara@arm.com (Andre Przywara)]

Hi,

On 26/07/18 10:32, Maxime Ripard wrote:
> On Thu, Jul 26, 2018 at 09:30:14AM +0100, Andre Przywara wrote:
>> Hi,
>>
>> On 26/07/18 08:42, Icenowy Zheng wrote:
>>>
>>>
>>> ? 2018?7?26? GMT+08:00 ??3:39:11, Maxime Ripard <maxime.ripard@bootlin.com> ??:
>>>> On Thu, Jul 26, 2018 at 01:35:20AM +0100, Andre Przywara wrote:
>>>>> From: Samuel Holland <samuel@sholland.org>
>>>>>
>>>>> The Orange Pi Win exposes several UARTs on header pin, and connects
>>>> one
>>>>> to the on-board WiFi/Bluetooth chip.
>>>>> Add the pinmux definitions to the UART nodes, but keep them disabled.
>>>>>
>>>>> Signed-off-by: Samuel Holland <samuel@sholland.org>
>>>>> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
>>>>> ---
>>>>>  .../boot/dts/allwinner/sun50i-a64-orangepi-win.dts | 33
>>>> ++++++++++++++++++++++
>>>>>  1 file changed, 33 insertions(+)
>>>>>
>>>>> diff --git
>>>> a/arch/arm64/boot/dts/allwinner/sun50i-a64-orangepi-win.dts
>>>> b/arch/arm64/boot/dts/allwinner/sun50i-a64-orangepi-win.dts
>>>>> index 0cadcd59edd9..10f63d0b99cb 100644
>>>>> --- a/arch/arm64/boot/dts/allwinner/sun50i-a64-orangepi-win.dts
>>>>> +++ b/arch/arm64/boot/dts/allwinner/sun50i-a64-orangepi-win.dts
>>>>> @@ -54,6 +54,10 @@
>>>>>  	aliases {
>>>>>  		ethernet0 = &emac;
>>>>>  		serial0 = &uart0;
>>>>> +		serial1 = &uart1;
>>>>> +		serial2 = &uart2;
>>>>> +		serial3 = &uart3;
>>>>> +		serial4 = &uart4;
>>>>>  	};
>>>>>  
>>>>>  	chosen {
>>>>> @@ -237,12 +241,41 @@
>>>>>  	vcc-hdmi-supply = <&reg_dldo1>;
>>>>>  };
>>>>>  
>>>>> +/* On debug connector */
>>>>>  &uart0 {
>>>>>  	pinctrl-names = "default";
>>>>>  	pinctrl-0 = <&uart0_pins_a>;
>>>>>  	status = "okay";
>>>>>  };
>>>>>  
>>>>> +/* Wi-Fi/BT */
>>>>> +&uart1 {
>>>>> +	pinctrl-names = "default";
>>>>> +	pinctrl-0 = <&uart1_pins>, <&uart1_rts_cts_pins>;
>>>>> +	status = "okay";
>>>>> +};
>>>>
>>>> What BT chip is there? Does it have serdev support? If so, that should
>>>> be enabled here.
>>>
>>> RTL8723BS, no serdev.
> 
> https://www.spinics.net/lists/linux-bluetooth/msg76376.html
> 
> Not very far off though.
> 
>> Yes. A while ago I managed to enable Bluetooth (on the Pine64 with the
>> same chip), but that involved a lot of hacking with a special userland
>> tool (not hciattach and no serdev).
>>
>> What this node means to say is: The UART1 is hardwired to some on-board
>> device and those pins are not available for GPIO, for instance.
>>
>> At least that was my understanding when it comes to enabling devices in
>> the DT. Is that correct?
> 
> Well, yes and no. Arguably, any device connected to the other side of
> the serial bus should have been there from the beginning. However,
> there wasn't any way to do that in Linux before serdev was introduced,
> so we weren't doing that. That resulted in hacky userspace tools to
> work around that, and other work arounds in the DT to for example
> tying BT resources (clock, regulators, resets) to the WiFi chip hoping
> that someone would use both all the time.
> 
> Now that it's just around the corner, we don't have any excuse to do
> these kind of hacks anymore.

That's true. Also I see that the serdev binding itself is not serdev
specific, it just puts the Bluetooth node as a child of an UART node.
But we would still need a compatible string for that child, wouldn't we?
I guess we can't autodetect this? From what I can see from Hans' series
there is no DT compatible string defined?

So do we just put a node there, specifying the resources it needs? Like
the wake-up interrupt or regulators, if any? And leave out the
compatible string, at least for now?

Cheers,
Andre.