linux-kernel - Re: [PATCH 6/6 v5] regmap: Incorporate the regcache core into regmap

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Date:	Mon, 19 Sep 2011 18:28:31 +0200
From:	Lars-Peter Clausen <lars@...afoo.de>
To:	Mark Brown <broonie@...nsource.wolfsonmicro.com>
CC:	Dimitris Papastamos <dp@...nsource.wolfsonmicro.com>,
	linux-kernel@...r.kernel.org, Liam Girdwood <lrg@...com>,
	Graeme Gregory <gg@...mlogic.co.uk>,
	Samuel Oritz <sameo@...ux.intel.com>
Subject: Re: [PATCH 6/6 v5] regmap: Incorporate the regcache core into regmap

On 09/19/2011 06:13 PM, Mark Brown wrote:
> On Mon, Sep 19, 2011 at 05:57:49PM +0200, Lars-Peter Clausen wrote:
>> On 09/19/2011 03:34 PM, Dimitris Papastamos wrote:
> 
>>> +	if (!map->cache_bypass) {
>>> +		ret = regcache_write(map, reg, val);
>>> +		if (!ret || map->cache_only)
>>> +			return 0;
> 
>> The hw write shouldn't be skipped if the cache write is successful. We should
>> only exit here if cache_only is set.
> 
> There's a couple of other issues too.  I've already got the following
> patch for this one locally:
> 
> --- a/drivers/base/regmap/regmap.c
> +++ b/drivers/base/regmap/regmap.c
> @@ -304,7 +304,9 @@ static int _regmap_write(struct regmap *map,
> unsigned int re
>  
>         if (!map->cache_bypass) {
>                 ret = regcache_write(map, reg, val);
> -               if (!ret || map->cache_only)
> +               if (ret != 0)
> +                       return ret;

Hm... last time we said we want to fallback to hw read/write even if the cache
operation has failed. The issue is that regcache_write will check for
regmap_writeable, so you'll get different behaviour if caching is enabled for
registers where regmap_writeable returns false.

> +               if (map->cache_only)
>                         return 0;
>         }
>  
>> I also wonder if we should pass the return value of regcache_write on to the
>> caller if cache_only is set.
> 
> Yup.
> 
>> Btw. what should happen if both cache_bypass and cache_only are set? Or is that
>> an invalid configuration?
> 
> That's not sensible.  Probably BUG_ON().

BUG_ON might be a bit to strict, if we wanted to allow cache_only to be enabled
through debugfs like it is done for ASoC right now.
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