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SubjectRe: [PATCH v2 1/2] acpi, spcr: Make SPCR avialable to other architectures
On 12/13/2017 06:45 AM, Lorenzo Pieralisi wrote:
>> +/*
>> + * Erratum 44 for QDF2432v1 and QDF2400v1 SoCs describes the BUSY bit as
>> + * occasionally getting stuck as 1. To avoid the potential for a hang, check
>> + * TXFE == 0 instead of BUSY == 1. This may not be suitable for all UART
>> + * implementations, so only do so if an affected platform is detected in
>> + * acpi_parse_spcr().
>> + */
>> +bool qdf2400_e44_present;
>> +EXPORT_SYMBOL(qdf2400_e44_present);
> My eyes, this is horrible but it is not introduced by this patch. It
> would have been much better if:
> drivers/tty/serial/amba-pl011.c
> parsed the SPCR table (again) to detect it instead of relying on this
> horrible exported flag.

I didn't want to put any ACPI code in amba-pl011.c, so putting it in
spcr.c made the most sense. I agree the global variable is ugly. If
you have a better idea, I'm all ears.

If it's any consolation, this erratum affects only 1.x silicon, which is
technically pre-production (although a lot of people have them). This
work-around will eventually be reverted.

>> diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
>> index 46505396869e..9ae98eeada76 100644
>> --- a/drivers/acpi/Kconfig
>> +++ b/drivers/acpi/Kconfig
>> @@ -79,7 +79,12 @@ config ACPI_DEBUGGER_USER
>> endif
>> - bool
>> + bool "ACPI Serial Port Console Redirection Support"
>> + default y if ARM64
> You need to remove the selection in arch/arm64 then. Also, moving away
> from a non-visible config may have consequences on ARM64, Graeme and
> Mark are more familiar with the SPCR dependencies so please chime in.

I did raise this as a concern in the previous version of the patch. I
also think it should not be a selectable option.

Keeping the "select" does force SPCR to be enabled on ARM64 ACPI
platforms, but if it's an option for x86, it should be an option for ARM.

Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm
Technologies, Inc. Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.

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