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Re: [PATCH v4 0/4] ACPI: parse the SPCR table

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  Re: [PATCH v4 0/4] ACPI: parse the SPCR table Aleksey Makarov <aleksey.makarov@linaro.org> - 2016-03-04 13:00 +0100
    Re: [PATCH v4 0/4] ACPI: parse the SPCR table Peter Hurley <peter@hurleysoftware.com> - 2016-03-04 16:50 +0100
      Re: [PATCH v4 0/4] ACPI: parse the SPCR table Aleksey Makarov <aleksey.makarov@linaro.org> - 2016-03-11 17:30 +0100

#1350178 — Re: [PATCH v4 0/4] ACPI: parse the SPCR table

On 03/03/2016 06:35 PM, Peter Hurley wrote:
> On 03/03/2016 03:59 AM, Aleksey Makarov wrote:
>>
>>
>> On 03/01/2016 06:31 PM, Peter Hurley wrote:
>>> On 02/29/2016 04:02 AM, Aleksey Makarov wrote:
>>>> 'ARM Server Base Boot Requirements' [1] mentions SPCR (Serial Port
>>>> Console Redirection Table) [2] as a mandatory ACPI table that
>>>> specifies the configuration of serial console.
>>>>
>>>> Introduce a new function acpi_console_check().  At the uart port
>>>> registration, this function checks if the ACPI SPCR table specifies
>>>> its argument of type struct uart_port to be a console
>>>> and if so calls add_preferred_console().
>>>
>>> How will a user enable an earlycon on the same console as the SPCR
>>> console if there is no DBG2 table?
>>
>> ...
>> [    0.000000] earlycon: pl11 at MMIO 0x0000000009000000 (options '')
>> [    0.000000] bootconsole [pl11] enabled
>> ...
>> [    0.000000] Kernel command line:  root=/dev/vda1 rw systemd.show_status=no acpi=force earlycon=pl011,0x9000000
>> ...
>> [    0.318248] ACPI: SPCR: adding preferred console [ttyAMA0]
>> [    0.318736] ARMH0011:00: ttyAMA0 at MMIO 0x9000000 (irq = 5, base_baud = 0) is a SBSA
>> [    0.319502] console [ttyAMA0] enabled
>> [    0.319502] console [ttyAMA0] enabled
>> [    0.319933] bootconsole [pl11] disabled
>> [    0.319933] bootconsole [pl11] disabled
>> ...
>>
>> Why?
> 
> That's pretty disingenuous; via command line?
> 
> By that measure, none of your patches are required because a user
> can already start both console and earlycon without them.
> 
> With the console location specified in the SPCR, earlycon should
> be opt-in on the command-line simply with "earlycon" command-line
> parameter.

Yes.  That's why we have SPCR *and* DBG2. 
DBG2 specifies where we should run earlycon.

>>> How will a user enable an earlycon on the same console as the SPCR
>>> console if there is no DBG2 table?

In no way.  You need DBG2 to run earlycon.

(If you don't want to specify it's address etc explicitly)

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#1350325

On 03/04/2016 03:53 AM, Aleksey Makarov wrote:
> 
> 
> On 03/03/2016 06:35 PM, Peter Hurley wrote:
>> On 03/03/2016 03:59 AM, Aleksey Makarov wrote:
>>>
>>>
>>> On 03/01/2016 06:31 PM, Peter Hurley wrote:
>>>> On 02/29/2016 04:02 AM, Aleksey Makarov wrote:
>>>>> 'ARM Server Base Boot Requirements' [1] mentions SPCR (Serial Port
>>>>> Console Redirection Table) [2] as a mandatory ACPI table that
>>>>> specifies the configuration of serial console.
>>>>>
>>>>> Introduce a new function acpi_console_check().  At the uart port
>>>>> registration, this function checks if the ACPI SPCR table specifies
>>>>> its argument of type struct uart_port to be a console
>>>>> and if so calls add_preferred_console().
>>>>
>>>> How will a user enable an earlycon on the same console as the SPCR
>>>> console if there is no DBG2 table?
>>>
>>> ...
>>> [    0.000000] earlycon: pl11 at MMIO 0x0000000009000000 (options '')
>>> [    0.000000] bootconsole [pl11] enabled
>>> ...
>>> [    0.000000] Kernel command line:  root=/dev/vda1 rw systemd.show_status=no acpi=force earlycon=pl011,0x9000000
>>> ...
>>> [    0.318248] ACPI: SPCR: adding preferred console [ttyAMA0]
>>> [    0.318736] ARMH0011:00: ttyAMA0 at MMIO 0x9000000 (irq = 5, base_baud = 0) is a SBSA
>>> [    0.319502] console [ttyAMA0] enabled
>>> [    0.319502] console [ttyAMA0] enabled
>>> [    0.319933] bootconsole [pl11] disabled
>>> [    0.319933] bootconsole [pl11] disabled
>>> ...
>>>
>>> Why?
>>
>> That's pretty disingenuous; via command line?
>>
>> By that measure, none of your patches are required because a user
>> can already start both console and earlycon without them.
>>
>> With the console location specified in the SPCR, earlycon should
>> be opt-in on the command-line simply with "earlycon" command-line
>> parameter.
> 
> Yes.  That's why we have SPCR *and* DBG2. 
> DBG2 specifies where we should run earlycon.
> 
>>>> How will a user enable an earlycon on the same console as the SPCR
>>>> console if there is no DBG2 table?
> 
> In no way.  You need DBG2 to run earlycon.

And that's an entirely arbitrary decision being made by you.
Which I think is unnecessarily limited.


> (If you don't want to specify it's address etc explicitly)

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#1356037

Hi Peter,

You are right, SPCR console should support earlycon.
I will send next version that will try to follow your recommendations in 
a week, after I return from vacations.

As we discussed with Christopher, "serial: pl011: use SPCR to setup 
32-bit access" will be dropped.

Thank you
Aleksey Makarov

On 04.03.2016 22:47, Peter Hurley wrote:
> On 03/04/2016 03:53 AM, Aleksey Makarov wrote:
>>
>>
>> On 03/03/2016 06:35 PM, Peter Hurley wrote:
>>> On 03/03/2016 03:59 AM, Aleksey Makarov wrote:
>>>>
>>>>
>>>> On 03/01/2016 06:31 PM, Peter Hurley wrote:
>>>>> On 02/29/2016 04:02 AM, Aleksey Makarov wrote:
>>>>>> 'ARM Server Base Boot Requirements' [1] mentions SPCR (Serial Port
>>>>>> Console Redirection Table) [2] as a mandatory ACPI table that
>>>>>> specifies the configuration of serial console.
>>>>>>
>>>>>> Introduce a new function acpi_console_check().  At the uart port
>>>>>> registration, this function checks if the ACPI SPCR table specifies
>>>>>> its argument of type struct uart_port to be a console
>>>>>> and if so calls add_preferred_console().
>>>>>
>>>>> How will a user enable an earlycon on the same console as the SPCR
>>>>> console if there is no DBG2 table?
>>>>
>>>> ...
>>>> [    0.000000] earlycon: pl11 at MMIO 0x0000000009000000 (options '')
>>>> [    0.000000] bootconsole [pl11] enabled
>>>> ...
>>>> [    0.000000] Kernel command line:  root=/dev/vda1 rw systemd.show_status=no acpi=force earlycon=pl011,0x9000000
>>>> ...
>>>> [    0.318248] ACPI: SPCR: adding preferred console [ttyAMA0]
>>>> [    0.318736] ARMH0011:00: ttyAMA0 at MMIO 0x9000000 (irq = 5, base_baud = 0) is a SBSA
>>>> [    0.319502] console [ttyAMA0] enabled
>>>> [    0.319502] console [ttyAMA0] enabled
>>>> [    0.319933] bootconsole [pl11] disabled
>>>> [    0.319933] bootconsole [pl11] disabled
>>>> ...
>>>>
>>>> Why?
>>>
>>> That's pretty disingenuous; via command line?
>>>
>>> By that measure, none of your patches are required because a user
>>> can already start both console and earlycon without them.
>>>
>>> With the console location specified in the SPCR, earlycon should
>>> be opt-in on the command-line simply with "earlycon" command-line
>>> parameter.
>>
>> Yes.  That's why we have SPCR *and* DBG2.
>> DBG2 specifies where we should run earlycon.
>>
>>>>> How will a user enable an earlycon on the same console as the SPCR
>>>>> console if there is no DBG2 table?
>>
>> In no way.  You need DBG2 to run earlycon.
>
> And that's an entirely arbitrary decision being made by you.
> Which I think is unnecessarily limited.
>
>
>> (If you don't want to specify it's address etc explicitly)
>
>

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