[PATCH 01/22] serial: 8250_dw: Add optional reset control support

Chen-Yu Tsai
2014-05-23T08:38:37Z

The Allwinner A31 and A23 SoCs have a reset controller
maintaining the UART in reset by default.

This patch adds optional reset support to the driver.

Signed-off-by: Chen-Yu Tsai <wens@csie.org>
---
Documentation/devicetree/bindings/serial/snps-dw-apb-uart.txt | 1 +
drivers/tty/serial/8250/8250_dw.c | 10 ++++++++++
2 files changed, 11 insertions(+)

diff --git a/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.txt b/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.txt
index f13f1c5..cb9af84 100644
--- a/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.txt
+++ b/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.txt
@@ -7,6 +7,7 @@ Required properties:
- clock-frequency : the input clock frequency for the UART.

Optional properties:
+- 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.
- reg-io-width : the size (in bytes) of the IO accesses that should be
diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index ed31135..d0c6d080 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -26,6 +26,7 @@
#include <linux/slab.h>
#include <linux/acpi.h>
#include <linux/clk.h>
+#include <linux/reset.h>
#include <linux/pm_runtime.h>

#include <asm/byteorder.h>
@@ -59,6 +60,7 @@ struct dw8250_data {
int last_mcr;
int line;
struct clk *clk;
+ struct reset_control *rst;
struct uart_8250_dma dma;
};

@@ -259,6 +261,8 @@ static int dw8250_probe_of(struct uart_port *p,
if (!of_property_read_u32(np, "reg-shift", &val))
p->regshift = val;

+ data->rst = devm_reset_control_get_optional(p->dev, NULL);
+
/* clock got configured through clk api, all done */
if (p->uartclk)
return 0;
@@ -362,6 +366,9 @@ static int dw8250_probe(struct platform_device *pdev)
return -ENODEV;
}

+ if (!IS_ERR_OR_NULL(data->rst))
+ reset_control_deassert(data->rst);
+
data->line = serial8250_register_8250_port(&uart);
if (data->line < 0)
return data->line;
@@ -382,6 +389,9 @@ static int dw8250_remove(struct platform_device *pdev)

serial8250_unregister_port(data->line);

+ if (!IS_ERR_OR_NULL(data->rst))
+ reset_control_assert(data->rst);
+
if (!IS_ERR(data->clk))
clk_disable_unprepare(data->clk);

--
2.0.0.rc2