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

[Jon Mason]

On Tue, Mar 14, 2017 at 8:32 AM, Rafał Miłecki <zajec5 at gmail.com> wrote:
> 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 at milecki.pl>
>>>
>>> This adds baud rate, parity & number of data bits. It's required to get
>>> serial working correctly.
>>>
>>> Signed-off-by: Rafa?? Mi??ecki <rafal at milecki.pl>
>>> ---
>>>  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.


It should work for all the boards.  The question is whether it should
be in the DTSI or DTS file.  This code replicates code I have in
arch/arm/boot/dts/bcm953012k.dts
So, either it should be removed or we should change all of the other
DTS files to have this entry.  My understanding is that the latter
approach is the acceptable one (which matches Andrew's comment), but I
can make the other changes if necessary.

Thanks,
Jon