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Commit 79a64832 authored by Loc Ho's avatar Loc Ho Committed by Rafael J. Wysocki
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ACPI: SPCR: Workaround for APM X-Gene 8250 UART 32-alignment errata 



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: default avatarLoc Ho <lho@apm.com>
Acked-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 2bece493

drivers/acpi/spcr.c

+22 −0
Original line number Diff line number Diff line
@@ -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);