[U-Boot] [PATCH] imx: serial: Wait for ongoing transmission to finish before serial reset

[Lukasz Majewski]

It may happen that the MXC serial IP block is performing some ongoing
transmission (started at e.g. board_init()) when the "initr_serial" is
called.

As a result the serial port IP block is reset, so transmitted data is
corrupted:

I2C:   ready
DRAM:  1 GiB
jSS('HH��SL_SDHC: 04 rev 0x0

This patch prevents from this situation, by waiting for transmission
complete bit set (UART Status Register 2 (UARTx_USR2), bit TXDC):

I2C:   ready
DRAM:  1 GiB
ID:    unit type 0x4 rev 0x0

Signed-off-by: Lukasz Majewski <lukma at denx.de>
---

 drivers/serial/serial_mxc.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/serial/serial_mxc.c b/drivers/serial/serial_mxc.c
index cce80a8..ef4eb12 100644
--- a/drivers/serial/serial_mxc.c
+++ b/drivers/serial/serial_mxc.c
@@ -141,6 +141,13 @@ struct mxc_uart {
 
 static void _mxc_serial_init(struct mxc_uart *base)
 {
+	/*
+	 * Wait for any ongoing transmission to finish - for example
+	 * from pre-relocation enabled UART
+	 */
+	while (!(readl(&base->sr2) & USR2_TXDC))
+		;
+
 	writel(0, &base->cr1);
 	writel(0, &base->cr2);
 
-- 
2.1.4