This is a note to let you know that I've just added the patch titled
MIPS: Add custom serial.h with BASE_BAUD override for generic kernel
to my tty git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git
in the tty-linus branch.
The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.
If you have any questions about this process, please let me know.
>From c8ec2041f549e7f2dee0c34d25381be6f7805f99 Mon Sep 17 00:00:00 2001
From: Matt Redfearn <matt.redfearn@xxxxxxxx>
Date: Tue, 28 Nov 2017 15:22:20 +0000
Subject: MIPS: Add custom serial.h with BASE_BAUD override for generic kernel
Add a custom serial.h header for MIPS, allowing platforms to override
the asm-generic version if required.
The generic platform uses this header to set BASE_BAUD to 0. The
generic platform supports multiple boards, which may have different
UART clocks. Also one of the boards supported is the Boston FPGA board,
where the UART clock depends on the loaded FPGA bitfile. As such there
is no way that the generic kernel can set a compile time default
BASE_BAUD.
Commit 31cb9a8575ca ("earlycon: initialise baud field of earlycon device
structure") changed the behavior of of_setup_earlycon such that any baud
rate set in the device tree is now set in the earlycon structure. The
UART driver will then calculate a divisor based on BASE_BAUD and set it.
With MIPS generic kernels this resulted in garbage output due to the
incorrect uart clock rate being used to calculate a divisor. This
commit, combined with "serial: 8250_early: Only set divisor if valid clk
& baud" prevents the earlycon code setting a bad divisor and restores
earlycon output.
Fixes: 31cb9a8575ca ("earlycon: initialise baud field of earlycon device structure")
Cc: stable <stable@xxxxxxxxxxxxxxx> # 4.14
Signed-off-by: Matt Redfearn <matt.redfearn@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/mips/include/asm/Kbuild | 1 -
arch/mips/include/asm/serial.h | 22 ++++++++++++++++++++++
2 files changed, 22 insertions(+), 1 deletion(-)
create mode 100644 arch/mips/include/asm/serial.h
diff --git a/arch/mips/include/asm/Kbuild b/arch/mips/include/asm/Kbuild
index 7c8aab23bce8..b1f66699677d 100644
--- a/arch/mips/include/asm/Kbuild
+++ b/arch/mips/include/asm/Kbuild
@@ -16,7 +16,6 @@ generic-y += qrwlock.h
generic-y += qspinlock.h
generic-y += sections.h
generic-y += segment.h
-generic-y += serial.h
generic-y += trace_clock.h
generic-y += unaligned.h
generic-y += user.h
diff --git a/arch/mips/include/asm/serial.h b/arch/mips/include/asm/serial.h
new file mode 100644
index 000000000000..1d830c6666c2
--- /dev/null
+++ b/arch/mips/include/asm/serial.h
@@ -0,0 +1,22 @@
+/*
+ * Copyright (C) 2017 MIPS Tech, LLC
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; either version 2 of the License, or (at your
+ * option) any later version.
+ */
+#ifndef __ASM__SERIAL_H
+#define __ASM__SERIAL_H
+
+#ifdef CONFIG_MIPS_GENERIC
+/*
+ * Generic kernels cannot know a correct value for all platforms at
+ * compile time. Set it to 0 to prevent 8250_early using it
+ */
+#define BASE_BAUD 0
+#else
+#include <asm-generic/serial.h>
+#endif
+
+#endif /* __ASM__SERIAL_H */
--
2.15.0