From: Loc Ho <lho@apm.com>
To: rafael@kernel.org, jon.mason@broadcom.com
Cc: jcm@redhat.com, rjw@rjwysocki.net, lenb@kernel.org,
robert.moore@intel.com, lv.zheng@intel.com,
linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org,
devel@acpica.org, bcm-kernel-feedback-list@broadcom.com,
aleksey.makarov@linaro.org, gregkh@linuxfoundation.org,
patches@apm.com, Loc Ho <lho@apm.com>
Subject: [PATCH v2 2/2] ACPI: SPCR: Workaround for APM X-Gene 8250 UART 32-alignment errata
Date: Mon, 3 Jul 2017 14:33:09 -0700 [thread overview]
Message-ID: <1499117589-4829-3-git-send-email-lho@apm.com> (raw)
In-Reply-To: <1499117589-4829-1-git-send-email-lho@apm.com>
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>
---
drivers/acpi/spcr.c | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)
diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c
index 2905063..4ac3e06 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);
--
1.8.3.1
next prev parent reply other threads:[~2017-07-03 21:33 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-03 21:33 [PATCH v2 0/2] ACPI: SPCR: Use access width to determine mmio usage Loc Ho
2017-07-03 21:33 ` [PATCH v2 1/2] " Loc Ho
2017-07-03 21:44 ` Rafael J. Wysocki
2017-07-04 7:22 ` Greg Kroah-Hartman
2017-07-03 21:33 ` Loc Ho [this message]
2017-07-03 21:45 ` [PATCH v2 2/2] ACPI: SPCR: Workaround for APM X-Gene 8250 UART 32-alignment errata Rafael J. Wysocki
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