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Subject[PATCH 1/1] tty: serial: owl: Add support for kernel debugger
Date
Implement poll_put_char and poll_get_char callbacks in struct uart_ops
that enables OWL UART to be used for KGDB debugging over serial line.

Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@gmail.com>
---
drivers/tty/serial/owl-uart.c | 45 ++++++++++++++++++++++++++++++-----
1 file changed, 39 insertions(+), 6 deletions(-)

diff --git a/drivers/tty/serial/owl-uart.c b/drivers/tty/serial/owl-uart.c
index c2fa2f15d50a..26dcc374dec5 100644
--- a/drivers/tty/serial/owl-uart.c
+++ b/drivers/tty/serial/owl-uart.c
@@ -12,6 +12,7 @@
#include <linux/console.h>
#include <linux/delay.h>
#include <linux/io.h>
+#include <linux/iopoll.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
@@ -20,13 +21,13 @@
#include <linux/tty.h>
#include <linux/tty_flip.h>

-#define OWL_UART_PORT_NUM 7
-#define OWL_UART_DEV_NAME "ttyOWL"
+#define OWL_UART_PORT_NUM 7
+#define OWL_UART_DEV_NAME "ttyOWL"

-#define OWL_UART_CTL 0x000
-#define OWL_UART_RXDAT 0x004
-#define OWL_UART_TXDAT 0x008
-#define OWL_UART_STAT 0x00c
+#define OWL_UART_CTL 0x000
+#define OWL_UART_RXDAT 0x004
+#define OWL_UART_TXDAT 0x008
+#define OWL_UART_STAT 0x00c

#define OWL_UART_CTL_DWLS_MASK GENMASK(1, 0)
#define OWL_UART_CTL_DWLS_5BITS (0x0 << 0)
@@ -461,6 +462,34 @@ static void owl_uart_config_port(struct uart_port *port, int flags)
}
}

+#ifdef CONFIG_CONSOLE_POLL
+
+static int owl_uart_poll_get_char(struct uart_port *port)
+{
+ u32 c = NO_POLL_CHAR;
+
+ if (!(owl_uart_read(port, OWL_UART_STAT) & OWL_UART_STAT_RFEM))
+ c = owl_uart_read(port, OWL_UART_RXDAT);
+
+ return c;
+}
+
+static void owl_uart_poll_put_char(struct uart_port *port, unsigned char c)
+{
+ /* Wait while TX FIFO is full */
+ while (owl_uart_read(port, OWL_UART_STAT) & OWL_UART_STAT_TFFU)
+ cpu_relax();
+
+ /* Send the character out */
+ owl_uart_write(port, c, OWL_UART_TXDAT);
+
+ /* Wait for transmitter to become empty */
+ while (owl_uart_read(port, OWL_UART_STAT) & OWL_UART_STAT_TRFL_MASK)
+ cpu_relax();
+}
+
+#endif /* CONFIG_CONSOLE_POLL */
+
static const struct uart_ops owl_uart_ops = {
.set_mctrl = owl_uart_set_mctrl,
.get_mctrl = owl_uart_get_mctrl,
@@ -476,6 +505,10 @@ static const struct uart_ops owl_uart_ops = {
.request_port = owl_uart_request_port,
.release_port = owl_uart_release_port,
.verify_port = owl_uart_verify_port,
+#ifdef CONFIG_CONSOLE_POLL
+ .poll_get_char = owl_uart_poll_get_char,
+ .poll_put_char = owl_uart_poll_put_char,
+#endif
};

#ifdef CONFIG_SERIAL_OWL_CONSOLE
--
2.26.2
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