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SubjectRe: [PATCH 1/2] acpi, spcr: Make SPCR avialable to other architectures
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On 12/07/2017 01:43 PM, Timur Tabi wrote:
> On Thu, Dec 7, 2017 at 11:29 AM, Prarit Bhargava <prarit@redhat.com> wrote:
>> Other architectures can use SPCR to setup an early console or console but
>> the current code is ARM64 specific.
>>
>> Change the name of parse_spcr() to acpi_parse_spcr(). Add a weak
>> function acpi_arch_setup_console() that can be used for arch-specific
>> setup. Move SPCR initialization flag into ACPI code. Update the
>> Documention on the use of the SPCR earlycon.
>>
>> This patch does not change arm64 behaviour.
>
> Let's hope so. Our E44 erratum work-around has caused lots of
> problems in the past, so the code is a bit fragile.
>
>> +static bool qdf2400_erratum_44_present(struct acpi_table_header *h)
>> +{
>> + if (memcmp(h->oem_id, "QCOM ", ACPI_OEM_ID_SIZE))
>> + return false;
>> +
>> + if (!memcmp(h->oem_table_id, "QDF2432 ", ACPI_OEM_TABLE_ID_SIZE))
>> + return true;
>> +
>> + if (!memcmp(h->oem_table_id, "QDF2400 ", ACPI_OEM_TABLE_ID_SIZE) &&
>> + h->oem_revision == 1)
>> + return true;
>> +
>> + return false;
>> +}
>
> Please give us a chance to test this patch before merging. We've had a
> lot of problems with our E44 work-around, and we need to make sure
> that qdf2400_erratum_44_present function is called before the pl011
> driver is probed.

Timor, do you know of a specific system that has this problem? If so, I
could see if we have one @ Red Hat and test on it to verify the WAR.

>
>> +
>> +/*
>> + * APM X-Gene v1 and v2 UART hardware is an 16550 like device but has its
>> + * register aligned to 32-bit. In addition, the BIOS also encoded the
>> + * access width to be 8 bits. This function detects this errata condition.
>> + */
>> +static bool xgene_8250_erratum_present(struct acpi_table_spcr *tb)
>> +{
>> + bool xgene_8250 = false;
>> +
>> + if (tb->interface_type != ACPI_DBG2_16550_COMPATIBLE)
>> + return false;
>> +
>> + if (memcmp(tb->header.oem_id, "APMC0D", ACPI_OEM_ID_SIZE) &&
>> + memcmp(tb->header.oem_id, "HPE ", ACPI_OEM_ID_SIZE))
>> + return false;
>> +
>> + if (!memcmp(tb->header.oem_table_id, "XGENESPC",
>> + ACPI_OEM_TABLE_ID_SIZE) && tb->header.oem_revision == 0)
>> + xgene_8250 = true;
>> +
>> + if (!memcmp(tb->header.oem_table_id, "ProLiant",
>> + ACPI_OEM_TABLE_ID_SIZE) && tb->header.oem_revision == 1)
>> + xgene_8250 = true;
>> +
>> + return xgene_8250;
>> +}
>
> I suspect that this function has the same issues as
> qdf2400_erratum_44_present().
>

Ditto.

>> +config ACPI_SPCR_TABLE
>> + bool "ACPI Serial Port Console Redirection Support"
>> + default y if ARM64
>> + help
>> + Enable support for Serial Port Console Redirection (SPCR) Table.
>> + This table provides information about the configuration of the
>> + earlycon console.
>> +
>
> So ACPI without SPCR has never been tested by us. Making it optional
> makes me a little nervous. We'll have to evaluate this change.
>

It is 'y' for ARM64? Maybe I have that wrong but I thought that would
always build it for ARM64.

P.

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