[alsa-devel] [PATCH 4/5] ASoC: fsl_ssi: use flat regmap cache

[Marek Vasut]

On 09/26/2016 09:13 PM, Mark Brown wrote:
> On Thu, Sep 22, 2016 at 05:27:42PM +0200, Marek Vasut wrote:
>> On 09/22/2016 04:37 PM, Maciej S. Szmigiero wrote:
> 
>>> There are three possible solutions:
>>> 1) Go back to RB tree cache (revert patch 4) and debug the lockdep warning,
>>> 2) Keep the flat cache introduced by patch 4 but debug the oops at
>>> cache init time (while keeping defaults read from hardware),
>>> 3) Keep both patches and risk the same issues that were previously
>>> caused by hardcoded register defaults in driver.
>>> However, Marek says the device works fine for him with the patches.
> 
>> I believe switching to flat cache is harmless and it should be a better
>> mode for devices with small mmio address spaces. After some discussion
>> on IRC, I believe [1] should resolve the RBTREE crash (?).
> 
> So, can we get a clear decision on this after testing?  The discussion
> here and the discussion on IRC are a bit disjointed and I'd like to make
> sure we end up with something that definitely works.
> 
I think 1,2,3,4 are certainly harmless. I think even 5 is harmless (at
least according to my testing on MX6Q and MX6SX, which is not the
greatest sample), but can be safely reverted if there are concerns.

I also believe the following two patches should be backported for stable
4.7 (they were part of tag 'regmap-fix-v4.8-rc5' of
git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regmap):

commit b2c7f5d9c939a37c1ce7f86a642de70e3033ee9e
Author: Maarten ter Huurne <maarten at treewalker.org>
Date:   Fri Jul 29 23:42:12 2016 +0200

    regmap: cache: Fix num_reg_defaults computation from reg_defaults_raw

commit 1bc8da4e143c0fd8807e061a66d91d5972601ab1
Author: Lars-Peter Clausen <lars at metafoo.de>
Date:   Thu Aug 4 17:22:16 2016 +0200

    regmap: rbtree: Avoid overlapping nodes

-- 
Best regards,
Marek Vasut