Patch "MIPS: Add custom serial.h with BASE_BAUD override for generic kernel" has been added to the 4.14-stable tree

Patch "MIPS: Add custom serial.h with BASE_BAUD override for generic kernel" has been added to the 4.14-stable tree

[gregkh]

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 the 4.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mips-add-custom-serial.h-with-base_baud-override-for-generic-kernel.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From c8ec2041f549e7f2dee0c34d25381be6f7805f99 Mon Sep 17 00:00:00 2001
From: Matt Redfearn <matt.redfearn@mips.com>
Date: Tue, 28 Nov 2017 15:22:20 +0000
Subject: MIPS: Add custom serial.h with BASE_BAUD override for generic kernel

From: Matt Redfearn <matt.redfearn@mips.com>

commit c8ec2041f549e7f2dee0c34d25381be6f7805f99 upstream.

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")
Signed-off-by: Matt Redfearn <matt.redfearn@mips.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/mips/include/asm/Kbuild   |    1 -
 arch/mips/include/asm/serial.h |   22 ++++++++++++++++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)

--- 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
--- /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 */


Patches currently in stable-queue which might be from matt.redfearn@mips.com are

queue-4.14/mips-add-custom-serial.h-with-base_baud-override-for-generic-kernel.patch
queue-4.14/serial-8250_early-only-set-divisor-if-valid-clk-baud.patch