linux-kernel - Re: [PATCH 07/18] regmap: mmio: add config option to allow relaxed MMIO accesses

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Message-ID: <87o8l581ql.fsf@collabora.com>
Date:   Wed, 14 Oct 2020 14:51:14 +0300
From:   Adrian Ratiu <adrian.ratiu@...labora.com>
To:     Mark Brown <broonie@...nel.org>,
        Adrian Ratiu <adrian.ratiu@...labora.com>
Cc:     Ezequiel Garcia <ezequiel@...labora.com>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Fruehberger Peter <Peter.Fruehberger@...bosch.com>,
        kuhanh.murugasen.krishnan@...el.com,
        Daniel Vetter <daniel@...ll.ch>, kernel@...labora.com,
        linux-media@...r.kernel.org, linux-rockchip@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 07/18] regmap: mmio: add config option to allow relaxed
 MMIO accesses

Hello Mark,

On Tue, 13 Oct 2020, Mark Brown <broonie@...nel.org> 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.

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!

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?

Kind regards,
Adrian