| From 97e914b7de3c943011779b979b8093fdc0d85722 Mon Sep 17 00:00:00 2001 |
| From: Mark Tomlinson <mark.tomlinson@alliedtelesis.co.nz> |
| Date: Wed, 12 Feb 2020 10:24:55 +1300 |
| Subject: MIPS: cavium_octeon: Fix syncw generation. |
| |
| From: Mark Tomlinson <mark.tomlinson@alliedtelesis.co.nz> |
| |
| commit 97e914b7de3c943011779b979b8093fdc0d85722 upstream. |
| |
| The Cavium Octeon CPU uses a special sync instruction for implementing |
| wmb, and due to a CPU bug, the instruction must appear twice. A macro |
| had been defined to hide this: |
| |
| #define __SYNC_rpt(type) (1 + (type == __SYNC_wmb)) |
| |
| which was intended to evaluate to 2 for __SYNC_wmb, and 1 for any other |
| type of sync. However, this expression is evaluated by the assembler, |
| and not the compiler, and the result of '==' in the assembler is 0 or |
| -1, not 0 or 1 as it is in C. The net result was wmb() producing no code |
| at all. The simple fix in this patch is to change the '+' to '-'. |
| |
| Fixes: bf92927251b3 ("MIPS: barrier: Add __SYNC() infrastructure") |
| Signed-off-by: Mark Tomlinson <mark.tomlinson@alliedtelesis.co.nz> |
| Tested-by: Chris Packham <chris.packham@alliedtelesis.co.nz> |
| Signed-off-by: Paul Burton <paulburton@kernel.org> |
| Cc: linux-mips@vger.kernel.org |
| Cc: linux-kernel@vger.kernel.org |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| arch/mips/include/asm/sync.h | 4 +++- |
| 1 file changed, 3 insertions(+), 1 deletion(-) |
| |
| --- a/arch/mips/include/asm/sync.h |
| +++ b/arch/mips/include/asm/sync.h |
| @@ -155,9 +155,11 @@ |
| * effective barrier as noted by commit 6b07d38aaa52 ("MIPS: Octeon: Use |
| * optimized memory barrier primitives."). Here we specify that the affected |
| * sync instructions should be emitted twice. |
| + * Note that this expression is evaluated by the assembler (not the compiler), |
| + * and that the assembler evaluates '==' as 0 or -1, not 0 or 1. |
| */ |
| #ifdef CONFIG_CPU_CAVIUM_OCTEON |
| -# define __SYNC_rpt(type) (1 + (type == __SYNC_wmb)) |
| +# define __SYNC_rpt(type) (1 - (type == __SYNC_wmb)) |
| #else |
| # define __SYNC_rpt(type) 1 |
| #endif |
