Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752133AbbGUGOh (ORCPT ); Tue, 21 Jul 2015 02:14:37 -0400 Received: from webbox1416.server-home.net ([77.236.96.61]:40352 "EHLO webbox1416.server-home.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750837AbbGUGOg (ORCPT ); Tue, 21 Jul 2015 02:14:36 -0400 From: Alexander Stein To: Mark Brown Cc: Greg Kroah-Hartman , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/1] regmap: regcache-rbtree: Use GFP_ATOMIC when using spinlocks Date: Tue, 21 Jul 2015 08:14:32 +0200 Message-ID: <8537578.XGSGY4If3j@ws-stein> User-Agent: KMail/4.14.8 (Linux/4.0.5-gentoo; KDE/4.14.8; x86_64; ; ) In-Reply-To: <20150720172627.GF11162@sirena.org.uk> References: <1437061732-21018-1-git-send-email-alexander.stein@systec-electronic.com> <3879923.hy2mOjvtRz@ws-stein> <20150720172627.GF11162@sirena.org.uk> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1985 Lines: 52 On Monday 20 July 2015 18:26:27, Mark Brown wrote: > > AFAICS even a flat cache seems also only be usefull when providing > > defaults, no? (Or having volatile registers). > > Well, it's *better* to provide defaults since otherwise everything > defaults to 0 but it does avoid the whole allocation during fast path > issue since it allocates the cache on init and perhaps that's OK. There is another reason for using REGCACHE_FLAT: Using regcache_cache_only (e.g. during suspend) which is not possible with REGCACHE_NONE. > > So how to handle this properly? Bail out, if fast_io is available and > > cache_type != (REGCACHE_NONE || REGCACHE_FLAT)? > > Or perhaps just if we have to do an allocation? I can see that someone > might want to use an rbtree and would be careful enough to do the init, > though I *am* a bit dubious about it. I'm feeling uncomfortable this warning occured only when (at least) CONFIG_LOCKDEP is enabled. It warns right ahead but only if you begged for it... Even if defaults are provided an extension to the register set (e.g. a more recent IP revision with more features) might not be synchronized with the defaults. Nobody might noticed until CONFIG_LOCKDEP is enabled and the register without defaults gets written. Best regards, Alexander -- Dipl.-Inf. Alexander Stein SYS TEC electronic GmbH alexander.stein@systec-electronic.com Legal and Commercial Address: Am Windrad 2 08468 Heinsdorfergrund Germany Office: +49 (0) 3765 38600-0 Fax: +49 (0) 3765 38600-4100 Managing Directors: Director Technology/CEO: Dipl.-Phys. Siegmar Schmidt; Director Commercial Affairs/COO: Dipl. Ing. (FH) Armin von Collrepp Commercial Registry: Amtsgericht Chemnitz, HRB 28082; USt.-Id Nr. DE150534010 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/