brcm2708: add kernel 4.14 support

[openwrt/staging/chunkeey.git] / target / linux / brcm2708 / patches-4.14 / 950-0121-amba_pl011-Insert-mb-for-correct-FIFO-handling.patch

diff --git a/target/linux/brcm2708/patches-4.14/950-0121-amba_pl011-Insert-mb-for-correct-FIFO-handling.patch b/target/linux/brcm2708/patches-4.14/950-0121-amba_pl011-Insert-mb-for-correct-FIFO-handling.patch
new file mode 100644 (file)
index 0000000..37fd83e
--- /dev/null
+++ b/target/linux/brcm2708/patches-4.14/950-0121-amba_pl011-Insert-mb-for-correct-FIFO-handling.patch
@@ -0,0 +1,27 @@
+From 436e9b301802720c0bf0f080301263c6e926d723 Mon Sep 17 00:00:00 2001
+From: Phil Elwell <phil@raspberrypi.org>
+Date: Fri, 29 Sep 2017 10:32:19 +0100
+Subject: [PATCH 121/454] amba_pl011: Insert mb() for correct FIFO handling
+
+The pl011 register accessor functions use the _relaxed versions of the
+standard readl() and writel() functions, meaning that there are no
+automatic memory barriers. When polling a FIFO status register to check
+for fullness, it is necessary to ensure that any outstanding writes have
+completed; otherwise the flags are effectively stale, making it possible
+that the next write is to a full FIFO.
+
+Signed-off-by: Phil Elwell <phil@raspberrypi.org>
+---
+ drivers/tty/serial/amba-pl011.c | 1 +
+ 1 file changed, 1 insertion(+)
+
+--- a/drivers/tty/serial/amba-pl011.c
++++ b/drivers/tty/serial/amba-pl011.c
+@@ -1403,6 +1403,7 @@ static bool pl011_tx_char(struct uart_am
+               return false; /* unable to transmit character */
+ 
+       pl011_write(c, uap, REG_DR);
++      mb();
+       uap->port.icount.tx++;
+ 
+       return true;