[PATCH 2/2] x86/config/efi: drop DRIVER_SERIAL_NS16550

[Ahmad Fatoum]

On 10/26/20 7:06 PM, Michael Olbrich wrote:
> On Tue, Oct 20, 2020 at 09:35:30AM +0200, Ahmad Fatoum wrote:
>> On 10/20/20 9:26 AM, Uwe Kleine-König wrote:
>>> On Tue, Oct 20, 2020 at 07:08:47AM +0200, Ahmad Fatoum wrote:
>>>> Hello Uwe,
>>>>
>>>> On 9/18/20 1:04 PM, Uwe Kleine-König wrote:
>>>>> For most machines having DRIVER_SERIAL_NS16550 and DRIVER_SERIAL_EFI_STDIO
>>>>> both enabled results in the output appearing twice on the serial output.
>>>>> So remove disable the lowlevel driver and rely on the EFI bios for serial.
>>>
>>> How embarrassing, s/remove //.
>>>
>>>> On the flip-side, some systems now won't output anything over serial with
>>>> the defconfig, like the one I just ran into. Maybe we should keep both
>>>> enabled, but have a quirk table, which boards to disable the 16550 for?
>>>
>>> Expecting that most systems are happy with EFI_STDIO I would suggest a
>>> quirk table for those systems which are not?!
>>
>> Doubled output is better than no output, so a defconfig that
>> by default displays anything if the BIOS is not in the quirk
>> table sounds like it's the better choice?
> 
> Maybe disable CONSOLE_ACTIVATE_ALL instead? Then you should only get the
> output from one driver.

And which one should be default? You'll get more compile time coverage
with the defconfig but the user experience problem of having a defconfig
that does print nothing at all on some devices is still there.

> 
> Michael
> 
>>>
>>>> My board is
>>>>   EFI v2.40 by American Megatrends v327691". What's yours?
>>>>   barebox at barebox EFI payload:/ devinfo acpi-FACP0
>>>>   [...]
>>>>   Revision: 5
>>>>   OemId: ALASKA
>>>>   OemTableId: A M I
>>>>   OemRevision: 17244169
>>>>   CreatorId: 0x20494d41
>>>>   CreatorRevision: 65555
>>>>
>>>> What's yours?
>>>
>>> I saw the doubled output on my Laptop (Lenovo T460p).
>>
>> You have serial output on your laptop?
>>
>>>
>>> dmidecode has:
>>>
>>> 	BIOS Information
>>> 		Vendor: LENOVO
>>> 		Version: R07ET81W (2.21 )
>>> 		Release Date: 12/18/2017
>>> 		Address: 0xE0000
>>> 		Runtime Size: 128 kB
>>> 		ROM Size: 16 MB
>>> 		Characteristics:
>>> 			PCI is supported
>>> 			PNP is supported
>>> 			BIOS is upgradeable
>>> 			BIOS shadowing is allowed
>>> 			Boot from CD is supported
>>> 			Selectable boot is supported
>>> 			EDD is supported
>>> 			3.5"/720 kB floppy services are supported (int 13h)
>>> 			Print screen service is supported (int 5h)
>>> 			8042 keyboard services are supported (int 9h)
>>> 			Serial services are supported (int 14h)
>>> 			Printer services are supported (int 17h)
>>> 			CGA/mono video services are supported (int 10h)
>>> 			ACPI is supported
>>> 			USB legacy is supported
>>> 			BIOS boot specification is supported
>>> 			Targeted content distribution is supported
>>> 			UEFI is supported
>>> 		BIOS Revision: 2.21
>>> 		Firmware Revision: 1.4
>>>
>>> (This is the system I write this mail on, I don't feel like rebooting to check
>>> devinfo in barebox, take a picture and then type the stuff into a mail
>>> by hand.)
>>>
>>> Best regards
>>> Uwe
>>>
>>>
>>
>> -- 
>> Pengutronix e.K.                           |                             |
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>>
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> 

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |