linux-kernel - Re: [PATCH v1 1/1] mfd: intel-lpss: Try to enable Memory-Write-Invalidate

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Message-ID: <20161110163939.GN1470@lahna.fi.intel.com>
Date:   Thu, 10 Nov 2016 18:39:39 +0200
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Lee Jones <lee.jones@...aro.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/1] mfd: intel-lpss: Try to enable
 Memory-Write-Invalidate

On Thu, Nov 10, 2016 at 05:22:40PM +0200, Andy Shevchenko wrote:
> On Thu, 2016-11-10 at 16:59 +0200, Mika Westerberg wrote:
> > On Thu, Nov 10, 2016 at 04:51:42PM +0200, Andy Shevchenko wrote:
> > > Enable MWI mechanism if PCI bus master supports it.
> > 
> > Why?
> 
> It might be potential benefit in some cases. Documentation says that
> standard Memory Write might supply more current data than in the CPU
> modified cache line and "trashing a line in the cache may trash some
> data that is more current that in the memory line". This allows to avoid
> potential retries and other performance degradation issues on the bus.
> Though, I dunno how to measure it.
> 
> Would be enough to extend commit message by this paragraph?

That's better, yes.