netdev - Re: [PATCH 1/2] regmap: Allow installing custom reg_update

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Message-ID: <20151002171908.GY12635@sirena.org.uk>
Date:	Fri, 2 Oct 2015 18:19:08 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Jon Ringle <jon@...gle.org>
Cc:	gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: [PATCH 1/2] regmap: Allow installing custom reg_update_bits
 function

On Thu, Oct 01, 2015 at 08:29:19AM -0400, Jon Ringle wrote:
> On Thu, 1 Oct 2015, Mark Brown wrote:

> > This completely bypasses and therefore breaks the cache infrastructure.

> Right after sending the v2 patch, I realized that calling the 
> custom reg_update_bits would only be applicable for registers that are 
> marked as volatile. Would the following solution be acceptable (it would 

Well, it should still *work* with a cache, though it's certainly true
that it's unlikely to have any performance benefit with cached register
since the read part of the read/modify/write cycle is essentially free 
with the cache.

> also simplify the regmap_update_bits in the encx24j600 driver):

> 	if (regmap_volatile(map, reg) && map->reg_update_bits) {
> 		return map->reg_update_bits(map->bus_context, reg, mask, 
> 		                            val, change, force_write);

> The cache state should not matter for volatile registers, right?

Right.  I see you've sent a new patch already, I'll reply to that after
I've thought about it a little.

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