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

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

Hi,

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?

> 
>> My board is
>>   EFI v2.40 by American Megatrends v327691". What's yours?
>>   barebox@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
> 
> 

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