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authorLoc Ho <lho@apm.com>2017-07-04 00:33:09 +0300
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2017-07-04 22:29:38 +0300
commit79a648328d2a604524a30523ca763fbeca0f70e3 (patch)
tree9d44cba925a86c9bc5d8b178e45dcc5291ddd1ba /drivers/acpi/spcr.c
parent2bece49394872d36bbc5767fd643deac05920c55 (diff)
downloadlinux-79a648328d2a604524a30523ca763fbeca0f70e3.tar.xz
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: Loc Ho <lho@apm.com> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'drivers/acpi/spcr.c')
-rw-r--r--drivers/acpi/spcr.c22
1 files changed, 22 insertions, 0 deletions
diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c
index 29050630f3da..4ac3e06b41d8 100644
--- a/drivers/acpi/spcr.c
+++ b/drivers/acpi/spcr.c
@@ -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);