[PATCH] SPCR: check bit width for the 16550 UART

[Aleksey Makarov]

Check the 'Register Bit Width' field of the ACPI Generic Address
Structure that specifies the address of the UART registers to
decide if the driver should use "mmio32" access instead of "mmio".

If the driver is other than 16550 the access with is defined
by the Interface Type field of the SPCR table.

For discussion:

https://lkml.kernel.org/r/7fa523de-3fbb-1566-f521-927143f73d1e@xxxxxxxxxx

Signed-off-by: Aleksey Makarov <aleksey.makarov@xxxxxxxxxx>
Signed-off-by: Graeme Gregory <graeme.gregory@xxxxxxxxxx>
Reported-by: Heyi Guo <heyi.guo@xxxxxxxxxx>
---
 drivers/acpi/spcr.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c
index e8d7bc7..6c6710b 100644
--- a/drivers/acpi/spcr.c
+++ b/drivers/acpi/spcr.c
@@ -70,6 +70,10 @@ int __init parse_spcr(bool earlycon)
 		break;
 	case ACPI_DBG2_16550_COMPATIBLE:
 	case ACPI_DBG2_16550_SUBSET:
+		if (table->serial_port.space_id ==
+			ACPI_ADR_SPACE_SYSTEM_MEMORY &&
+		    table->serial_port.bit_width == 32)
+			iotype = "mmio32";
 		uart = "uart";
 		break;
 	default:
-- 
2.10.2