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 <jmas...@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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