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>
---
drivers/acpi/spcr.c | 25 +++++++++++++++++++++++++
drivers/tty/serial/amba-pl011.c | 2 ++
include/linux/acpi.h | 5 +++++
3 files changed, 32 insertions(+)
diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c
index a1eca91..a5e241d 100644
--- a/drivers/acpi/spcr.c
+++ b/drivers/acpi/spcr.c
@@ -95,3 +95,28 @@ bool acpi_console_check(struct uart_port *uport)
return acpi_table_parse_spcr(spcr_table_handler_check, uport) > 0;
}
+
+static int spcr_table_handler_32_bit(struct acpi_table_spcr *table, void *data)
+{
+ 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_parse_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 500232a..d9ca3a4 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -2541,6 +2541,8 @@ 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/acpi.h b/include/linux/acpi.h
index ea0c297..da1eb23 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -1007,11 +1007,16 @@ static inline struct fwnode_handle *acpi_get_next_subnode(struct device *dev,
struct uart_port;
#ifdef CONFIG_ACPI_SPCR_TABLE
bool acpi_console_check(struct uart_port *uport);
+bool acpi_console_sbsa_32bit(void);
#else
static inline bool acpi_console_check(struct uart_port *uport)
{
return FALSE;
}
+static inline bool acpi_console_sbsa_32bit(void)
+{
+ return false;
+}
#endif
#endif /*_LINUX_ACPI_H*/
--
2.7.1
--
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