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ACPI: SPCR: Workaround for APM X-Gene 8250 UART 32-alignment errata

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APM X-Gene verion 1 and 2 have an 8250 UART with its register
aligned to 32-bit. In addition, the latest released BIOS
encodes the access field as 8-bit access instead 32-bit access.
This causes no console with ACPI boot as the console
will not match X-Gene UART port due to the lack of mmio32
option.

Signed-off-by: Loc Ho <lho@apm.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
Loc Ho 2017-07-03 14:33:09 -07:00 committed by Rafael J. Wysocki
parent 2bece49394
commit 79a648328d
1 changed files with 22 additions and 0 deletions
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22
drivers/acpi/spcr.c
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@ -36,6 +36,26 @@ static bool qdf2400_erratum_44_present(struct acpi_table_header *h)
return false;
}
/*
* 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)
{
if (tb->interface_type != ACPI_DBG2_16550_COMPATIBLE)
return false;
if (memcmp(tb->header.oem_id, "APMC0D", ACPI_OEM_ID_SIZE))
return false;
if (!memcmp(tb->header.oem_table_id, "XGENESPC",
ACPI_OEM_TABLE_ID_SIZE) && tb->header.oem_revision == 0)
return true;
return false;
}
/**
* parse_spcr() - parse ACPI SPCR table and add preferred console
*
@ -129,6 +149,8 @@ int __init parse_spcr(bool earlycon)
if (qdf2400_erratum_44_present(&table->header))
uart = "qdf2400_e44";
if (xgene_8250_erratum_present(table))
iotype = "mmio32";
snprintf(opts, sizeof(opts), "%s,%s,0x%llx,%d", uart, iotype,
table->serial_port.address, baud_rate);