Some implementations of ARM SBSA serial port hardware require that access
to the registers should be 32-bit. Unfortunately, the only way for
the driver to tell if it's the case is to use the data from ACPI SPCR/DBG2
tables. In this case the value of the 'Interface Type' field of the SPCR
table is ACPI_DBG2_ARM_SBSA_32BIT.
How this value is described in the DBG2 spec:
"(deprecated) ARM SBSA (2.x only) Generic UART supporting only
32-bit accesses"
Signed-off-by: Aleksey Makarov <aleksey.makarov@xxxxxxxxxx>
Tested-by: Christopher Covington <cov@xxxxxxxxxxxxxx>
---
drivers/acpi/spcr.c | 29 +++++++++++++++++++++++++++++
drivers/tty/serial/amba-pl011.c | 2 ++
include/linux/console.h | 5 +++++
3 files changed, 36 insertions(+)
diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c
index 0475840..df1741f 100644
--- a/drivers/acpi/spcr.c
+++ b/drivers/acpi/spcr.c
@@ -75,3 +75,32 @@ int acpi_console_match(struct console *console, char **options)
return acpi_table_parse2(ACPI_SIG_SPCR, spcr_table_handler_match, &d);
}
+
+static int spcr_table_handler_32_bit(struct acpi_table_header *t,
+ void *data)
+{
+ struct acpi_table_spcr *table = (struct acpi_table_spcr *)t;
+
+ return table->interface_type == ACPI_DBG2_ARM_SBSA_32BIT;
+}
+
+/**
+ * acpi_console_sbsa_32bit - Tell if SPCR specifies 32-bit SBSA.
+ *
+ * Some implementations of ARM SBSA serial port hardware require that access
+ * to the registers should be 32-bit. Unfortunately, the only way for
+ * the driver to tell if it's the case is to use the data from ACPI SPCR/DBG2
+ * tables. In this case the value of the 'Interface Type' field of the SPCR
+ * table is ACPI_DBG2_ARM_SBSA_32BIT.
+ *
+ * Return: true if access should be 32-bit wide.
+ */
+bool acpi_console_sbsa_32bit(void)
+{
+ if (acpi_disabled)
+ return false;
+
+ return acpi_table_parse2(ACPI_SIG_SPCR,
+ spcr_table_handler_32_bit, NULL) > 0;
+}
+EXPORT_SYMBOL(acpi_console_sbsa_32bit);
diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index f613bff..699a3ce 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -2563,6 +2563,8 @@ static int sbsa_uart_probe(struct platform_device *pdev)
baudrate = 115200;
}
+ vendor_sbsa.access_32b = acpi_console_sbsa_32bit();
+
portnr = pl011_find_free_port();
if (portnr < 0)
return portnr;
diff --git a/include/linux/console.h b/include/linux/console.h
index dcc2b59..027ef50 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -137,11 +137,16 @@ struct console {
#ifdef CONFIG_ACPI_SPCR_TABLE
int acpi_console_match(struct console *c, char **options);
+bool acpi_console_sbsa_32bit(void);
#else
static inline int acpi_console_match(struct console *c, char **options)
{
return -ENODEV;
}
+static inline bool acpi_console_sbsa_32bit(void)
+{
+ return false;
+}
#endif
/*
--
2.7.0
--
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