From: Chen-Yu Tsai <wens@xxxxxxxx>
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@xxxxxxxx>
Acked-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
(cherry picked from commit 7fe090bf48b522de8cd6fe85e2b3252ed74e74f8)
Signed-off-by: Chang Rebecca Swee Fun <rebecca.swee.fun.chang@xxxxxxxxx>
---
.../bindings/serial/snps-dw-apb-uart.txt | 1 +
drivers/tty/serial/8250/8250_dw.c | 9 +++++++++
2 files changed, 10 insertions(+)
diff --git a/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.txt b/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.txt
index 095ac71..7f76214 100644
--- a/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.txt
+++ b/Documentation/devicetree/bindings/serial/snps-dw-apb-uart.txt
@@ -15,6 +15,7 @@ The supplying peripheral clock can also be handled, needing a second property
Required elements: "baudclk", "apb_pclk"
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 affdcb1..501db2f 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>
@@ -60,6 +61,7 @@ struct dw8250_data {
int line;
struct clk *clk;
struct clk *pclk;
+ struct reset_control *rst;
struct uart_8250_dma dma;
};
@@ -383,6 +385,10 @@ static int dw8250_probe(struct platform_device *pdev)
}
}
+ data->rst = devm_reset_control_get_optional(&pdev->dev, NULL);
+ if (!IS_ERR(data->rst))
+ reset_control_deassert(data->rst);
+
data->dma.rx_chan_id = -1;
data->dma.tx_chan_id = -1;
data->dma.rx_param = data;
@@ -426,6 +432,9 @@ static int dw8250_remove(struct platform_device *pdev)
serial8250_unregister_port(data->line);
+ if (!IS_ERR(data->rst))
+ reset_control_assert(data->rst);
+
if (!IS_ERR(data->pclk))
clk_disable_unprepare(data->pclk);
--
1.7.9.5
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