commit 15b79ffee4e7a0e93600f588047b16a9b0bfb4dc
author Alexander Graf <agraf@suse.de> Wed Mar 07 22:08:24 2018 +0100
committer Tom Rini <trini@konsulko.com> Fri Mar 09 12:26:47 2018 -0500
tree 7363cceb00829d0c77806e927e9214b29834953b
parent e4ec7c0f8d46aef91d7dc59aa6a2c5b95cebd224

serial_bcm283x_mu: Flush RX queue after setting baud rate

After the UART was initialized, we may still have bogus data in the
RX queue if it was enabled with incorrect pin muxing before.

So let's flush the RX queue whenever we initialize baud rates.

This fixes a regression with the dynamic pinmuxing code when enable_uart=1
is not set in config.txt.

Fixes: caf2233b28 ("bcm283x: Add pinctrl driver")
Reported-by: Göran Lundberg <goran@lundberg.email>
Reported-by: Peter Robinson <pbrobinson@gmail.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
Tested-by: Peter Robinson <pbrobinson@gmail.com>
Tested-by: Tuomas Tynkkynen <tuomas@tuxera.com>

drivers/serial/serial_bcm283x_mu.c

diff --git a/drivers/serial/serial_bcm283x_mu.c b/drivers/serial/serial_bcm283x_mu.c
index 40029fa..d87b44e 100644
--- a/drivers/serial/serial_bcm283x_mu.c
+++ b/drivers/serial/serial_bcm283x_mu.c
@@ -51,6 +51,8 @@
 	struct bcm283x_mu_regs *regs;
 };
 
+static int bcm283x_mu_serial_getc(struct udevice *dev);
+
 static int bcm283x_mu_serial_setbrg(struct udevice *dev, int baudrate)
 {
 	struct bcm283x_mu_serial_platdata *plat = dev_get_platdata(dev);
@@ -59,13 +61,17 @@
 	u32 divider;
 
 	if (plat->skip_init)
-		return 0;
+		goto out;
 
 	divider = plat->clock / (baudrate * 8);
 
 	writel(BCM283X_MU_LCR_DATA_SIZE_8, &regs->lcr);
 	writel(divider - 1, &regs->baud);
 
+out:
+	/* Flush the RX queue - all data in there is bogus */
+	while (bcm283x_mu_serial_getc(dev) != -EAGAIN) ;
+
 	return 0;
 }