serial: protect access to serial rx buffer

Add test to avoid access to rx buffer when this buffer is empty.
In this case directly call getc() function to avoid issue when tstc()
is not called.

Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

diff --git a/drivers/serial/serial-uclass.c b/drivers/serial/serial-uclass.c
index 321d23ee93bf5c8d909e2309742eac28eb776671..4121a37aa80c661bbdcf46da8794e376206843f0 100644 (file)
--- a/drivers/serial/serial-uclass.c
+++ b/drivers/serial/serial-uclass.c
@@ -228,6 +228,9 @@ static int _serial_getc(struct udevice *dev)
        struct serial_dev_priv *upriv = dev_get_uclass_priv(dev);
        char val;
 
+       if (upriv->rd_ptr == upriv->wr_ptr)
+               return __serial_getc(dev);
+
        val = upriv->buf[upriv->rd_ptr++];
        upriv->rd_ptr %= CONFIG_SERIAL_RX_BUFFER_SIZE;