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

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Hi,

Am 29.05.20 um 17:50 schrieb 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.ciocaltea@xxxxxxxxx>
---
  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

Please do not unnecessarily re-indent kernel code. You can do so when you're actually adding something new.

#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();
+}

How is this different from earlycon? I dislike that this is being open-coded. Please try to reuse existing functions for this.

Regards,
Andreas

+
+#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



--
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
GF: Felix Imendörffer
HRB 36809 (AG Nürnberg)

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