[PATCH 1/1] tty: serial: owl: Add support for kernel debugger

[Cristian Ciocaltea]

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.ciocal...@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