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Subject[PATCH 1/2] tty: serial: meson_uart: Add support for kernel debugger
Date
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>
---
drivers/tty/serial/meson_uart.c | 46 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 46 insertions(+)

diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c
index 8a84259..49b20da 100644
--- a/drivers/tty/serial/meson_uart.c
+++ b/drivers/tty/serial/meson_uart.c
@@ -426,6 +426,48 @@ 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;
+
+ spin_lock_irqsave(&port->lock, flags);
+
+ while (!(readl(port->membase + AML_UART_STATUS) & AML_UART_TX_EMPTY))
+ cpu_relax();
+
+ writel(c, port->membase + AML_UART_WFIFO);
+
+ while (!(readl(port->membase + AML_UART_STATUS) & AML_UART_TX_EMPTY))
+ cpu_relax();
+
+ 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 +483,10 @@ 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
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