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Message-ID: <5e4876ff.1c69fb81.7b887.cb6e@mx.google.com>
Date:   Sat, 15 Feb 2020 14:55:58 -0800
From:   Paul Burton <paulburton@kernel.org>
To:     Mark Tomlinson <mark.tomlinson@alliedtelesis.co.nz>
CC:     paulburton@kernel.org, linux-mips@vger.kernel.org
CC:     chris.packham@alliedtelesis.co.nz, linux-kernel@vger.kernel.org,
        Mark Tomlinson <mark.tomlinson@alliedtelesis.co.nz>
CC:     linux-mips@vger.kernel.org
Subject: Re: [PATCH] MIPS: cavium_octeon: Fix syncw generation.
References:  <20200211212455.3307-1-mark.tomlinson@alliedtelesis.co.nz>
In-Reply-To:  <20200211212455.3307-1-mark.tomlinson@alliedtelesis.co.nz>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Hello,

Mark Tomlinson wrote:
> 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 '-'.

Applied to mips-fixes.

> commit 97e914b7de3c
> https://git.kernel.org/mips/c/97e914b7de3c
> 
> 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>

Thanks,
    Paul

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