Re: [PATCH 1/2] ARM: dts: BCM5301X: Specify serial console parameters

["Rafał Miłecki" <zajec5-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On 03/14/2017 01:26 PM, Andrew Lunn wrote:
> On Tue, Mar 14, 2017 at 08:58:29AM +0100, Rafa?? Mi??ecki wrote:
>> From: Rafa?? Mi??ecki <rafal-g1n6cQUeyibVItvQsEIGlw@public.gmane.org>
>>
>> This adds baud rate, parity & number of data bits. It's required to get
>> serial working correctly.
>>
>> Signed-off-by: Rafa?? Mi??ecki <rafal-g1n6cQUeyibVItvQsEIGlw@public.gmane.org>
>> ---
>>  arch/arm/boot/dts/bcm5301x.dtsi | 6 +++++-
>>  1 file changed, 5 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm/boot/dts/bcm5301x.dtsi b/arch/arm/boot/dts/bcm5301x.dtsi
>> index 8fd1ef9f0c2d..468107166a6f 100644
>> --- a/arch/arm/boot/dts/bcm5301x.dtsi
>> +++ b/arch/arm/boot/dts/bcm5301x.dtsi
>> @@ -18,8 +18,12 @@
>>  / {
>>  	interrupt-parent = <&gic>;
>>
>> +	aliases {
>> +		serial0 = &uart0;
>> +	};
>> +
>>  	chosen {
>> -		stdout-path = &uart0;
>> +		stdout-path = "serial0:115200n8";
>>  	};
>
> Hi Rafal
>
> The alias is fine. But putting the stdout-path here is unusual. Which
> serial port is used for console is board specific, where as
> bcm5301x.dtsi is very generic, it describes the SoC, not a board.  If
> you look at other .dtsi files, those that specify stdout-path contain
> properties which are common to a range of similar boards.

So far I've never seen any board using other uart. Also uart0 is disabled by
default and we enable it per board family (BCM4708 / BCM47081 / BCM4709 /
BCM47094). I think it's just more practical to have simple DTS that covers
99,9% boards by default and handled that margin of devices separately.

We already got a lot of duplicated code for enabling uart0, see:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=7b790d3b2943bf8e7e7bafe184008bd6451fe0bd

Jon Mason from Broadcom who knows this hardware and designs very well confirmed
it's a sane/safe assumption.
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