If the DW_apb_uart is configured with UART_16550_COMPATIBLE
configuration parameter set, then the Busy Functionality is
not available. These UARTs will never generate the Busy
detect indication interrupt, and therefore don't need
handling for it.
This creates a small optimization for the DW_apb_uarts
configured without the busy functionality, but more
importantly, it removes the small but real risk of hitting
potential issues caused by busy functionality handling when
no busy functionality exist.
Signed-off-by: Heikki Krogerus <heikki.krogerus@xxxxxxxxxxxxxxx>
---
.../devicetree/bindings/serial/snps-dw-apb-uart.txt | 3 +++
drivers/tty/serial/8250/8250_dw.c | 21 ++++++++++++++++++++-
2 files changed, 23 insertions(+), 1 deletion(-)
diff --git a/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.txt b/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.txt
index 289c40e..12bbe9f 100644
--- a/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.txt
+++ b/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.txt
@@ -15,6 +15,9 @@ The supplying peripheral clock can also be handled, needing a second property
Required elements: "baudclk", "apb_pclk"
Optional properties:
+- snps,uart-16550-compatible : reflects the value of UART_16550_COMPATIBLE
+ configuration parameter. Define this if your UART does not implement the busy
+ functionality.
- resets : phandle to the parent reset controller.
- reg-shift : quantity to shift the register offsets by. If this property is
not present then the register offsets are not shifted.
diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index 715215a..1ca7d75 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -65,6 +65,7 @@ struct dw8250_data {
struct uart_8250_dma dma;
unsigned skip_autocfg:1;
+ unsigned uart_16550_compatible:1;
};
#define BYT_PRV_CLK 0x800
@@ -314,11 +315,20 @@ static void dw8250_quirks(struct uart_port *p, struct dw8250_data *data)
}
#endif
} else if (has_acpi_companion(p->dev)) {
+ const struct acpi_device_id *id;
+
p->iotype = UPIO_MEM32;
p->regshift = 2;
p->serial_in = dw8250_serial_in32;
p->serial_out = dw8250_serial_out32;
- p->set_termios = dw8250_set_termios;
+
+ id = acpi_match_device(p->dev->driver->acpi_match_table, p->dev);
+ if ((id && strcmp(id->id, "AMD0020") &&
+ strcmp(id->id, "APMC0D08")) || !id) {
+ /* Intel platforms don't have Busy Functionality */
+ p->set_termios = dw8250_set_termios;
+ data->uart_16550_compatible = true;
+ }
}
/* Platforms with iDMA */
@@ -375,6 +385,9 @@ static int dw8250_probe(struct platform_device *pdev)
data->usr_reg = DW_UART_USR;
p->private_data = data;
+ data->uart_16550_compatible = device_property_read_bool(p->dev,
+ "snps,uart-16550-compatible");
+
err = device_property_read_u32(p->dev, "reg-shift", &val);
if (!err)
p->regshift = val;
@@ -461,6 +474,12 @@ static int dw8250_probe(struct platform_device *pdev)
dw8250_quirks(p, data);
+ /* If the Busy Functionality is not implemented, don't handle it */
+ if (data->uart_16550_compatible) {
+ p->serial_out = NULL;
+ p->handle_irq = NULL;
+ }
+
if (!data->skip_autocfg)
dw8250_setup_port(&uart);
--
2.5.1
--
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