Linux-Amlogic Archive on lore.kernel.org
 help / Atom feed
* [PATCH v2] tty: serial: meson_uart: Add support for kernel debugger
@ 2019-02-07 17:11 Julien Masson
  2019-02-15 23:15 ` Kevin Hilman
  0 siblings, 1 reply; 2+ messages in thread
From: Julien Masson @ 2019-02-07 17:11 UTC (permalink / raw)
  To: Kevin Hilman, Greg Kroah-Hartman
  Cc: Julien Masson, linux-kernel, linux-serial, Jiri Slaby,
	linux-amlogic, linux-arm-kernel

The kgdb invokes the poll_put_char and poll_get_char when communicating
with the host. This patch implement the serial polling hooks for the
meson_uart to be used for KGDB debugging over serial line.

Signed-off-by: Julien Masson <jmasson@baylibre.com>
---

Changes since v1 [0]:
* Use readl_poll_timeout_atomic instead of looping with read + cpu_relax
  -> read every 5 usecs during 1 msec
* add some comments

[0]: https://lore.kernel.org/lkml/1549015162-17418-1-git-send-email-jmasson@baylibre.com

 drivers/tty/serial/meson_uart.c | 65 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 65 insertions(+)

diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c
index 8a84259..bcff572 100644
--- a/drivers/tty/serial/meson_uart.c
+++ b/drivers/tty/serial/meson_uart.c
@@ -14,6 +14,7 @@
 #include <linux/delay.h>
 #include <linux/init.h>
 #include <linux/io.h>
+#include <linux/iopoll.h>
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/of.h>
@@ -75,6 +76,8 @@
 #define AML_UART_PORT_NUM		6
 #define AML_UART_DEV_NAME		"ttyAML"
 
+#define AML_UART_POLL_USEC		5
+#define AML_UART_TIMEOUT_USEC		1000
 
 static struct uart_driver meson_uart_driver;
 
@@ -426,6 +429,64 @@ static void meson_uart_config_port(struct uart_port *port, int flags)
 	}
 }
 
+#ifdef CONFIG_CONSOLE_POLL
+/*
+ * Console polling routines for writing and reading from the uart while
+ * in an interrupt or debug context (i.e. kgdb).
+ */
+
+static int meson_uart_poll_get_char(struct uart_port *port)
+{
+	u32 c;
+	unsigned long flags;
+
+	spin_lock_irqsave(&port->lock, flags);
+
+	if (readl(port->membase + AML_UART_STATUS) & AML_UART_RX_EMPTY)
+		c = NO_POLL_CHAR;
+	else
+		c = readl(port->membase + AML_UART_RFIFO);
+
+	spin_unlock_irqrestore(&port->lock, flags);
+
+	return c;
+}
+
+static void meson_uart_poll_put_char(struct uart_port *port, unsigned char c)
+{
+	unsigned long flags;
+	u32 reg;
+	int ret;
+
+	spin_lock_irqsave(&port->lock, flags);
+
+	/* Wait until FIFO is empty or timeout */
+	ret = readl_poll_timeout_atomic(port->membase + AML_UART_STATUS, reg,
+					reg & AML_UART_TX_EMPTY,
+					AML_UART_POLL_USEC,
+					AML_UART_TIMEOUT_USEC);
+	if (ret == -ETIMEDOUT) {
+		dev_err(port->dev, "Timeout waiting for UART TX EMPTY\n");
+		goto out;
+	}
+
+	/* Write the character */
+	writel(c, port->membase + AML_UART_WFIFO);
+
+	/* Wait until FIFO is empty or timeout */
+	ret = readl_poll_timeout_atomic(port->membase + AML_UART_STATUS, reg,
+					reg & AML_UART_TX_EMPTY,
+					AML_UART_POLL_USEC,
+					AML_UART_TIMEOUT_USEC);
+	if (ret == -ETIMEDOUT)
+		dev_err(port->dev, "Timeout waiting for UART TX EMPTY\n");
+
+out:
+	spin_unlock_irqrestore(&port->lock, flags);
+}
+
+#endif /* CONFIG_CONSOLE_POLL */
+
 static const struct uart_ops meson_uart_ops = {
 	.set_mctrl      = meson_uart_set_mctrl,
 	.get_mctrl      = meson_uart_get_mctrl,
@@ -441,6 +502,10 @@ static const struct uart_ops meson_uart_ops = {
 	.request_port	= meson_uart_request_port,
 	.release_port	= meson_uart_release_port,
 	.verify_port	= meson_uart_verify_port,
+#ifdef CONFIG_CONSOLE_POLL
+	.poll_get_char	= meson_uart_poll_get_char,
+	.poll_put_char	= meson_uart_poll_put_char,
+#endif
 };
 
 #ifdef CONFIG_SERIAL_MESON_CONSOLE
-- 
2.7.4


_______________________________________________
linux-amlogic mailing list
linux-amlogic@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-amlogic

^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [PATCH v2] tty: serial: meson_uart: Add support for kernel debugger
  2019-02-07 17:11 [PATCH v2] tty: serial: meson_uart: Add support for kernel debugger Julien Masson
@ 2019-02-15 23:15 ` Kevin Hilman
  0 siblings, 0 replies; 2+ messages in thread
From: Kevin Hilman @ 2019-02-15 23:15 UTC (permalink / raw)
  To: Julien Masson, Greg Kroah-Hartman
  Cc: Julien Masson, linux-kernel, linux-serial, Jiri Slaby,
	linux-amlogic, linux-arm-kernel

Julien Masson <jmasson@baylibre.com> writes:

> The kgdb invokes the poll_put_char and poll_get_char when communicating
> with the host. This patch implement the serial polling hooks for the
> meson_uart to be used for KGDB debugging over serial line.
>
> Signed-off-by: Julien Masson <jmasson@baylibre.com>

Looks good, and very useful thanks!

I'm adding this to a testing branch which will get included into the
'integ' branch of my amlogic tree for some broader testing.

Kevin

_______________________________________________
linux-amlogic mailing list
linux-amlogic@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-amlogic

^ permalink raw reply	[flat|nested] 2+ messages in thread

end of thread, back to index

Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-02-07 17:11 [PATCH v2] tty: serial: meson_uart: Add support for kernel debugger Julien Masson
2019-02-15 23:15 ` Kevin Hilman

Linux-Amlogic Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-amlogic/0 linux-amlogic/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-amlogic linux-amlogic/ https://lore.kernel.org/linux-amlogic \
		linux-amlogic@lists.infradead.org linux-amlogic@archiver.kernel.org
	public-inbox-index linux-amlogic


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.infradead.lists.linux-amlogic


AGPL code for this site: git clone https://public-inbox.org/ public-inbox