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From: Stefan Agner <stefan@agner.ch>
To: Mark Brown <broonie@kernel.org>
Cc: peterz@infradead.org, mingo@redhat.com,
	linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org
Subject: Re: Lockdep warning when using REGCACHE_RBTREE
Date: Fri, 15 Jan 2016 11:08:31 -0800	[thread overview]
Message-ID: <593bcd768227b953c0fc87cc0e5b175d@agner.ch> (raw)
In-Reply-To: <20160115162832.GY6588@sirena.org.uk>

On 2016-01-15 08:28, Mark Brown wrote:
> On Thu, Jan 14, 2016 at 05:14:47PM -0800, Stefan Agner wrote:
> 
>> On a slightly other topic, I question whether REGCACHE_RBTREE is the
>> right cache type for the DCU DRM driver. The driver has uses a regmap
>> area of 1144 32-bit registers, the most space is used by the layer
>> configuration registers which are 0x40 apart and 0x0-0x20 for each layer
>> are actually used (hence somewhat above 50%).
> 
>> Would FLAT be the better cache type?
> 
> Yes, and if it's a MMIO device the performance of a flat cache is more
> in line with the device performance.

Thanks for confirming that. I will switch to REGCACHE_FLAT then, I found
a second driver with the very same issue, also a MMIO mapped device:
drivers/pwm/pwm-fsl-ftm.c...

--
Stefan
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WARNING: multiple messages have this Message-ID (diff)
From: Stefan Agner <stefan@agner.ch>
To: Mark Brown <broonie@kernel.org>
Cc: festevam@gmail.com, peterz@infradead.org, mingo@redhat.com,
	linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org
Subject: Re: Lockdep warning when using REGCACHE_RBTREE
Date: Fri, 15 Jan 2016 11:08:31 -0800	[thread overview]
Message-ID: <593bcd768227b953c0fc87cc0e5b175d@agner.ch> (raw)
In-Reply-To: <20160115162832.GY6588@sirena.org.uk>

On 2016-01-15 08:28, Mark Brown wrote:
> On Thu, Jan 14, 2016 at 05:14:47PM -0800, Stefan Agner wrote:
> 
>> On a slightly other topic, I question whether REGCACHE_RBTREE is the
>> right cache type for the DCU DRM driver. The driver has uses a regmap
>> area of 1144 32-bit registers, the most space is used by the layer
>> configuration registers which are 0x40 apart and 0x0-0x20 for each layer
>> are actually used (hence somewhat above 50%).
> 
>> Would FLAT be the better cache type?
> 
> Yes, and if it's a MMIO device the performance of a flat cache is more
> in line with the device performance.

Thanks for confirming that. I will switch to REGCACHE_FLAT then, I found
a second driver with the very same issue, also a MMIO mapped device:
drivers/pwm/pwm-fsl-ftm.c...

--
Stefan

  reply	other threads:[~2016-01-15 19:10 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-01-14 22:30 Lockdep warning when using REGCACHE_RBTREE Stefan Agner
2016-01-14 22:30 ` Stefan Agner
2016-01-15  0:01 ` Mark Brown
2016-01-15  1:14   ` Stefan Agner
2016-01-15  1:14     ` Stefan Agner
2016-01-15 16:28     ` Mark Brown
2016-01-15 16:28       ` Mark Brown
2016-01-15 19:08       ` Stefan Agner [this message]
2016-01-15 19:08         ` Stefan Agner
2016-01-15  9:45 ` Peter Zijlstra
2016-01-15  9:45   ` Peter Zijlstra
2016-01-15 11:49   ` Mark Brown
2016-01-15 11:49     ` Mark Brown

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