brcm47xx: revert upstream commit breaking BCM4718A1

This fixes kernel hang when booting on BCM4718A1 (& probably BCM4717A1).

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
(cherry picked from commit 4c1aa64b4d804e77dfaa8d53e5ef699fcced4b18)
Fixes: aaecfecdcde5 ("kernel: bump kernel 4.4 to version 4.4.139")

diff --git a/target/linux/brcm47xx/patches-4.4/330-Revert-MIPS-BCM47XX-Enable-74K-Core-ExternalSync-for.patch b/target/linux/brcm47xx/patches-4.4/330-Revert-MIPS-BCM47XX-Enable-74K-Core-ExternalSync-for.patch
new file mode 100644 (file)
index 0000000..e6cf500
--- /dev/null
+++ b/target/linux/brcm47xx/patches-4.4/330-Revert-MIPS-BCM47XX-Enable-74K-Core-ExternalSync-for.patch
@@ -0,0 +1,76 @@
+From: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <rafal@milecki.pl>
+Date: Fri, 27 Jul 2018 12:39:01 +0200
+Subject: [PATCH] Revert "MIPS: BCM47XX: Enable 74K Core ExternalSync for PCIe
+ erratum"
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+This reverts commit 2a027b47dba6b77ab8c8e47b589ae9bbc5ac6175.
+
+Enabling ExternalSync caused a regression for BCM4718A1 (used e.g. in
+Netgear E3000 and ASUS RT-N16): it simply hangs during PCIe
+initialization. It's likely that BCM4717A1 is also affected.
+
+I didn't notice that earlier as the only BCM47XX devices with PCIe I
+own are:
+1) BCM4706 with 2 x 14e4:4331
+2) BCM4706 with 14e4:4360 and 14e4:4331
+it appears that BCM4706 is unaffected.
+
+While BCM5300X-ES300-RDS.pdf seems to document that erratum and its
+workarounds (according to quotes provided by Tokunori) it seems not even
+Broadcom follows them.
+
+According to the provided info Broadcom should define CONF7_ES in their
+SDK's mipsinc.h and implement workaround in the si_mips_init(). Checking
+both didn't reveal such code. It *could* mean Broadcom also had some
+problems with the given workaround.
+
+Reported-by: Michael Marley <michael@michaelmarley.com>
+Cc: Tokunori Ikegami <ikegami@allied-telesis.co.jp>
+Cc: Paul Burton <paul.burton@mips.com>
+Cc: Hauke Mehrtens <hauke@hauke-m.de>
+Cc: Chris Packham <chris.packham@alliedtelesis.co.nz>
+Cc: stable@vger.kernel.org
+Cc: James Hogan <jhogan@kernel.org>
+Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
+---
+ arch/mips/bcm47xx/setup.c        | 6 ------
+ arch/mips/include/asm/mipsregs.h | 3 ---
+ 2 files changed, 9 deletions(-)
+
+--- a/arch/mips/bcm47xx/setup.c
++++ b/arch/mips/bcm47xx/setup.c
+@@ -249,12 +249,6 @@ static int __init bcm47xx_cpu_fixes(void
+                */
+               if (bcm47xx_bus.bcma.bus.chipinfo.id == BCMA_CHIP_ID_BCM4706)
+                       cpu_wait = NULL;
+-
+-              /*
+-               * BCM47XX Erratum "R10: PCIe Transactions Periodically Fail"
+-               * Enable ExternalSync for sync instruction to take effect
+-               */
+-              set_c0_config7(MIPS_CONF7_ES);
+               break;
+ #endif
+       }
+--- a/arch/mips/include/asm/mipsregs.h
++++ b/arch/mips/include/asm/mipsregs.h
+@@ -605,8 +605,6 @@
+ #define MIPS_CONF7_WII                (_ULCAST_(1) << 31)
+ 
+ #define MIPS_CONF7_RPS                (_ULCAST_(1) << 2)
+-/* ExternalSync */
+-#define MIPS_CONF7_ES         (_ULCAST_(1) << 8)
+ 
+ #define MIPS_CONF7_IAR                (_ULCAST_(1) << 10)
+ #define MIPS_CONF7_AR         (_ULCAST_(1) << 16)
+@@ -2014,7 +2012,6 @@ __BUILD_SET_C0(status)
+ __BUILD_SET_C0(cause)
+ __BUILD_SET_C0(config)
+ __BUILD_SET_C0(config5)
+-__BUILD_SET_C0(config7)
+ __BUILD_SET_C0(intcontrol)
+ __BUILD_SET_C0(intctl)
+ __BUILD_SET_C0(srsmap)