From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, UNPARSEABLE_RELAY autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4D139C433E7 for ; Wed, 14 Oct 2020 12:59:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F22CB20BED for ; Wed, 14 Oct 2020 12:59:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388216AbgJNM7i (ORCPT ); Wed, 14 Oct 2020 08:59:38 -0400 Received: from bhuna.collabora.co.uk ([46.235.227.227]:46556 "EHLO bhuna.collabora.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727187AbgJNM7i (ORCPT ); Wed, 14 Oct 2020 08:59:38 -0400 Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: aratiu) with ESMTPSA id CC77C1F41295 From: Adrian Ratiu To: Mark Brown , Adrian Ratiu Cc: Ezequiel Garcia , Philipp Zabel , Mauro Carvalho Chehab , Fruehberger Peter , kuhanh.murugasen.krishnan@intel.com, Daniel Vetter , kernel@collabora.com, linux-media@vger.kernel.org, linux-rockchip@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 07/18] regmap: mmio: add config option to allow relaxed MMIO accesses In-Reply-To: <20201014121249.GA4580@sirena.org.uk> References: <20201012205957.889185-1-adrian.ratiu@collabora.com> <20201012205957.889185-8-adrian.ratiu@collabora.com> <20201013102656.GA5425@sirena.org.uk> <87o8l581ql.fsf@collabora.com> <20201014121249.GA4580@sirena.org.uk> Date: Wed, 14 Oct 2020 16:00:38 +0300 Message-ID: <87lfg97yix.fsf@collabora.com> MIME-Version: 1.0 Content-Type: text/plain; format=flowed Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 14 Oct 2020, Mark Brown wrote: > On Wed, Oct 14, 2020 at 02:51:14PM +0300, Adrian Ratiu wrote: >> On Tue, 13 Oct 2020, Mark Brown wrote: >> > On Mon, Oct 12, 2020 at 11:59:46PM +0300, Adrian Ratiu wrote: > >> > > - writeb(val, ctx->regs + reg); + if >> > > (ctx->relaxed_mmio) + writeb_relaxed(val, ctx->regs + reg); >> > > + else + writeb(val, ctx->regs + reg); > >> > There is no point in doing a conditional operation on every >> > I/O, it'd be better to register a different set of ops when >> > doing relaxed I/O. > >> Indeed I have considered adding new functions but went with >> this solution because it's easier for the users to only have to >> define a "relaxed" config then test the regmap ctx as above. > > It seems like you've taken this in a direction other than what > I was thinking of here - defining separate ops doesn't mean we > have to do anything which has any impact on the interface seen > by users. The regmap config is supplied at registration time, > it's just as available then as it is when doing I/O. Right. I got confused by the meaning of ops :) Sorry about that. > >> Thinking a bit more about it, yes, it makes more sense to have >> dedicated ops: this way users don't have to be explicit about >> adding membarriers and can combine relaxed and non-relaxed more >> easily, so it's also a better API trade-off in addition to >> avoiding the conditional. Thanks! > > I'm not sure what you're proposing here - it does seem useful to > be able to combine relaxed and non-relaxed I/O but that seems > like it'd break down the abstraction for regmap since tht's not > really a concept other buses are going to have? Unless we > provide an operation to switch by setting flags or somethin > possibly and integrate it with the cache perhaps. Could you be > a bit more specific about what you were thinking of here please? I was thinking about exposing a relaxed API like regmap_write_relaxed but now that I know what you meant by ops and also that it doesn't make sense for other busses / violates the abstraction, I realize that is a bad idea and I will continue improving this to avoid the conditional and send a separete patch. Thanks again! > >> Question: Do you want me to split this patch from the series and send it >> separately just for the regmap subsystem to be easier to review / apply? > > Sure.