greybus: uart: wait for credits on shutdown

We should try to wait until all credits are accounted
for before returning from shutdown.

For this purpose add a helper function that will
wait on completion, and call it form the shutdown.
This helper will also be useful when "wait until sent" is
implemented.

Signed-off-by: Axel Haslam <ahaslam@baylibre.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

diff --git a/drivers/staging/greybus/uart.c b/drivers/staging/greybus/uart.c
index 7dc9f9b873b198439a960ab5f9347b77c720e900..a2fca3b3358e9295c60f117c6fa62af0003b6b6b 100644 (file)
--- a/drivers/staging/greybus/uart.c
+++ b/drivers/staging/greybus/uart.c
@@ -29,6 +29,7 @@
 #include <linux/kdev_t.h>
 #include <linux/kfifo.h>
 #include <linux/workqueue.h>
+#include <linux/completion.h>
 
 #include "greybus.h"
 #include "gbphy.h"
@@ -39,6 +40,7 @@
 #define GB_UART_WRITE_FIFO_SIZE                PAGE_SIZE
 #define GB_UART_WRITE_ROOM_MARGIN      1       /* leave some space in fifo */
 #define GB_UART_FIRMWARE_CREDITS       4096
+#define GB_UART_CREDIT_WAIT_TIMEOUT_MSEC       10000
 
 struct gb_tty_line_coding {
        __le32  rate;
@@ -71,6 +73,7 @@ struct gb_tty {
        struct kfifo write_fifo;
        bool close_pending;
        unsigned int credits;
+       struct completion credits_complete;
 };
 
 static struct tty_driver *gb_tty_driver;
@@ -197,6 +200,9 @@ static int gb_uart_receive_credits_handler(struct gb_operation *op)
         */
        tty_port_tty_wakeup(&gb_tty->port);
 
+       if (gb_tty->credits == GB_UART_FIRMWARE_CREDITS)
+               complete(&gb_tty->credits_complete);
+
        return ret;
 }
 
@@ -317,6 +323,24 @@ static int send_break(struct gb_tty *gb_tty, u8 state)
                                 &request, sizeof(request), NULL, 0);
 }
 
+static int gb_uart_wait_for_all_credits(struct gb_tty *gb_tty)
+{
+       int ret;
+
+       if (gb_tty->credits == GB_UART_FIRMWARE_CREDITS)
+               return 0;
+
+       ret = wait_for_completion_timeout(&gb_tty->credits_complete,
+                       msecs_to_jiffies(GB_UART_CREDIT_WAIT_TIMEOUT_MSEC));
+       if (!ret) {
+               dev_err(&gb_tty->gbphy_dev->dev,
+                       "time out waiting for credits\n");
+               return -ETIMEDOUT;
+       }
+
+       return 0;
+}
+
 static int gb_uart_flush(struct gb_tty *gb_tty, u8 flags)
 {
        struct gb_uart_serial_flush_request request;
@@ -765,12 +789,18 @@ static void gb_tty_port_shutdown(struct tty_port *port)
        kfifo_reset_out(&gb_tty->write_fifo);
        spin_unlock_irqrestore(&gb_tty->write_lock, flags);
 
+       if (gb_tty->credits == GB_UART_FIRMWARE_CREDITS)
+               goto out;
+
        ret = gb_uart_flush(gb_tty, GB_SERIAL_FLAG_FLUSH_TRANSMITTER);
        if (ret) {
                dev_err(&gb_tty->gbphy_dev->dev,
                        "error flushing transmitter: %d\n", ret);
        }
 
+       gb_uart_wait_for_all_credits(gb_tty);
+
+out:
        gb_tty->close_pending = false;
 }
 
@@ -842,6 +872,7 @@ static int gb_uart_probe(struct gbphy_device *gbphy_dev,
                goto exit_buf_free;
 
        gb_tty->credits = GB_UART_FIRMWARE_CREDITS;
+       init_completion(&gb_tty->credits_complete);
 
        minor = alloc_minor(gb_tty);
        if (minor < 0) {