[PATCH v2 1/1] tty: serial: owl: Add support for kernel debugger

Cristian Ciocaltea
2021-01-05T17:03:04Z

Implement 'poll_put_char' and 'poll_get_char' callbacks in struct
'owl_uart_ops' that enables OWL UART to be used for kernel debugging
over serial line.

Signed-off-by: Cristian Ciocaltea <cristian.ciocaltea@gmail.com>
---
Changes in v2:
- Reverted unnecessary changes per Andreas feedback
- Optimized implementation for 'owl_uart_poll_get_char()'
and 'owl_uart_poll_put_char()' callbacks

drivers/tty/serial/owl-uart.c | 25 +++++++++++++++++++++++++
1 file changed, 25 insertions(+)

diff --git a/drivers/tty/serial/owl-uart.c b/drivers/tty/serial/owl-uart.c
index c149f8c30007..54b24669ebc5 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>
@@ -461,6 +462,26 @@ 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)
+{
+ if (owl_uart_read(port, OWL_UART_STAT) & OWL_UART_STAT_RFEM)
+ return NO_POLL_CHAR;
+
+ return owl_uart_read(port, OWL_UART_RXDAT);
+}
+
+static void owl_uart_poll_put_char(struct uart_port *port, unsigned char ch)
+{
+ while (owl_uart_read(port, OWL_UART_STAT) & OWL_UART_STAT_TFFU)
+ cpu_relax();
+
+ owl_uart_write(port, ch, OWL_UART_TXDAT);
+}
+
+#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 +497,10 @@ 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
--
2.30.0