linux-kernel - Re: [PATCH 2/2] ARM: dts: sun8i: enable UART1 for iNet D978 Rev2 board

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Date:   Thu, 25 Aug 2016 17:13:15 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Icenowy Zheng <icenowy@...c.xyz>,
        Maxime Ripard <maxime.ripard@...e-electrons.com>
Cc:     Chen-Yu Tsai <wens@...e.org>, Russell King <linux@...linux.org.uk>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] ARM: dts: sun8i: enable UART1 for iNet D978 Rev2
 board

HI,

On 25-08-16 16:53, Icenowy Zheng wrote:
>
>
> 25.08.2016, 22:18, "Hans de Goede" <hdegoede@...hat.com>:
>> Hi,
>>
>> On 25-08-16 16:12, Icenowy Zheng wrote:
>>>  25.08.2016, 16:03, "Maxime Ripard" <maxime.ripard@...e-electrons.com>:
>>>>  Hi,
>>>>
>>>>  On Thu, Aug 25, 2016 at 02:57:24PM +0800, Icenowy Zheng wrote:
>>>>>   >>>> diff --git a/arch/arm/boot/dts/sun8i-a33-inet-d978-rev2.dts b/arch/arm/boot/dts/sun8i-a33-inet-d978-rev2.dts
>>>>>   >>>> index 78823d8..3ac22d4 100644
>>>>>   >>>> --- a/arch/arm/boot/dts/sun8i-a33-inet-d978-rev2.dts
>>>>>   >>>> +++ b/arch/arm/boot/dts/sun8i-a33-inet-d978-rev2.dts
>>>>>   >>>> @@ -48,6 +48,10 @@
>>>>>   >>>> model = "INet-D978 Rev 02";
>>>>>   >>>> compatible = "primux,inet-d978-rev2", "allwinner,sun8i-a33";
>>>>>   >>>>
>>>>>   >>>> + aliases {
>>>>>   >>>> + serial1 = &uart1;
>>>>>   >>>> + };
>>>>>   >>>> +
>>>>>   >>>
>>>>>   >>> Is there any other UART in the system?
>>>>>   >>
>>>>>   >> serial0 is defined in sun8i-reference-design-tablet.dtsi, as r_uart.
>>>>>   >
>>>>>   > If your board does not have r_uart pads, then the right thing to do
>>>>>   > would be to disable it. You can then have uart1 as serial0.
>>>>>
>>>>>   I don't know it. The RX/TX is wired on PF2/PF4 on the board (UART0 muxed with
>>>>>   MMC)
>>>>
>>>>  Then you don't support it and you need to disable it.
>>>>
>>>>>   But many codes will require a ttyS0 as console... So I think the
>>>>>   bluetooth should be located at ttyS1...
>>>>
>>>>  Most of them would use /dev/console anyway. What do you have in mind?
>>>
>>>  As a general configuration, /dev/ttyS0 will be indicated as the default console=
>>>  value... (Otherwise more boards will fail)
>>>
>>>  Or maybe we can specify uart0 as serial0, and leave it as disabled? (Thus if the
>>>  debug port is needed, we can easily apply a overlay with &mmc0 status as disabled,
>>>  and &uart0 status as okay)
>>>
>>>  On all my A33 boards, the official boot0, u-boot all uses uart0 as debugging port.
>>
>> If no uart is available (and being muxed with the mmc counts as not being available)
>> then you should not have any serial alias in the dts.
>>
>> In u-boot you need to use:
>>
>> # CONFIG_REQUIRE_SERIAL_CONSOLE is not set
>>
>> In the defconfig in this case, otherwise u-boot is going to be unhappy about
>> not having a serial console.
>
> It's not the problem.
>
> Can I have no ttyS0 and just make bluetooth ttyS1?

Ah, yes having a serial1 alias should do that I believe and I agree that it
is probably better to not use ttyS0 for the bluetooth uart.

Regards,

Hans