linux-kernel - Re: Lockdep warning when using REGCACHE

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Message-ID: <593bcd768227b953c0fc87cc0e5b175d@agner.ch>
Date:	Fri, 15 Jan 2016 11:08:31 -0800
From:	Stefan Agner <stefan@...er.ch>
To:	Mark Brown <broonie@...nel.org>
Cc:	festevam@...il.com, peterz@...radead.org, mingo@...hat.com,
	linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org
Subject: Re: Lockdep warning when using REGCACHE_RBTREE

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