linux-kernel - Re: [PATCH v5.1 1/2] ARM64: dts: meson-gx: use stable UART bindings with correct gate clock

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Date:   Mon, 4 Dec 2017 09:52:34 +0100
From:   Neil Armstrong <narmstrong@...libre.com>
To:     Andreas Färber <afaerber@...e.de>,
        khilman@...libre.com, Helmut Klein <hgkr.klein@...il.com>
Cc:     Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org
Subject: Re: [PATCH v5.1 1/2] ARM64: dts: meson-gx: use stable UART bindings
 with correct gate clock

On 04/12/2017 01:16, Andreas Färber wrote:
> Am 03.12.2017 um 15:15 schrieb Andreas Färber:
>> Hi,
>>
>> Am 21.06.2017 um 16:42 schrieb Neil Armstrong:
>>> diff --git a/arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi b/arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi
>>> index 17d3efd..ea53cc2 100644
>>> --- a/arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi
>>> +++ b/arch/arm64/boot/dts/amlogic/meson-gxbb.dtsi
>>> @@ -682,6 +682,31 @@
>>>  	clocks = <&clkc CLKID_SPI>;
>>>  };
>>>  
>>> +&uart_A {
>>> +	clocks = <&xtal>, <&clkc CLKID_UART0>, <&xtal>;
>>> +	clock-names = "xtal", "pclk", "baud";
>>> +};
>>> +
>>> +&uart_AO {
>>> +	clocks = <&xtal>, <&clkc CLKID_CLK81>, <&xtal>;
>>> +	clock-names = "xtal", "pclk", "baud";
>>> +};
>>> +
>>> +&uart_AO_B {
>>> +	clocks = <&xtal>, <&clkc CLKID_CLK81>, <&xtal>;
>>> +	clock-names = "xtal", "pclk", "baud";
>>> +};
>>> +
>>> +&uart_B {
>>> +	clocks = <&xtal>, <&clkc CLKID_UART1>, <&xtal>;
>>> +	clock-names = "xtal", "core", "baud";
>>
>> Looking at the meson_uart driver, it only looks for a "pclk" clock,
>> never for "core", and the only unnamed clock used should be the first.
>>
>> There is no bindings documentation for "core", so I assume this was an
>> oversight and should be "pclk" everywhere?
>>
>>> +};
>>> +
>>> +&uart_C {
>>> +	clocks = <&xtal>, <&clkc CLKID_UART2>, <&xtal>;
>>> +	clock-names = "xtal", "core", "baud";
>>> +};
>>
>> The issue I'm facing is that uart_C on NanoPi K2 is not working in
>> 4.14.1. To my surprise it appears to be probing okay though.
> 
> In 4.14 the serial driver checks for the legacy compatible and if
> present (even alongside the new compatible) always takes the legacy code
> path, using only the first clock, thus not tripping over "core" and not
> enabling the "pclk" if supplied.

I only used UART_A, this explains a lot.

> 
> This was changed for v4.15-rc1, so we should start seeing errors for
> missing "pclk" clocks.
> 
>> Sadly just overwriting the clock-names property via overlay does not fix
>> my issue. Any ideas?

You need to rebind the devices.

> 
> For reference here's my latest overlay, overriding compatible, too:
> https://github.com/afaerber/dt-overlays/blob/master/meson-gxbb-nanopi-k2%2Barpi600%2Bnucleo-lrwan1.dts
> 
> Regards,
> Andreas
> 

Wow I must have been very tired when pushing this....

Thanks for spotting this.

I'll send a fix asap.

Neil