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Mon, 10 May 2021 15:48:47 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 45BB9168F; Mon, 10 May 2021 08:48:37 -0700 (PDT) Received: from arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 94E753F73B; Mon, 10 May 2021 08:48:36 -0700 (PDT) Date: Mon, 10 May 2021 16:47:23 +0100 From: Dave Martin To: Mark Brown Cc: Catalin Marinas , Will Deacon , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH v1 1/3] arm64/sve: Split _sve_flush macro into separate Z, P and FFR flushes Message-ID: <20210510153159.GA4187@arm.com> References: <20210510122348.56443-1-broonie@kernel.org> <20210510122348.56443-2-broonie@kernel.org> <20210510145710.GB18631@e103592.cambridge.arm.com> <20210510152253.GB4496@sirena.org.uk> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210510152253.GB4496@sirena.org.uk> User-Agent: Mutt/1.5.23 (2014-03-12) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210510_084845_760141_63DDA817 X-CRM114-Status: GOOD ( 19.71 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, May 10, 2021 at 04:22:53PM +0100, Mark Brown wrote: > On Mon, May 10, 2021 at 03:57:11PM +0100, Dave P Martin wrote: > > > > +.macro sve_flush_ffr > > > _sve_wrffr 0 > > > This doesn't flush the FFR as advertised, but writes whatever happens to > > be in P0 to the FFR. > > Oh, bother - the way the macros work mean the argument isn't super clear > there, it looks like it writes an immediate value, and then of course > the generated code looks identical. Will fix. > > > Thinking about it, is there ever a situation when we would want to flush > > the P-regs and not the FFR (or vice-versa)? I can't see where we would > > want to do that myself. > > > If not, can we keep these combined? We could either keep the name > > sve_flush_p (since the FFR is a predicate register, if a weird kind of > > one), or go with something more descriptive such as sve_flush_p_and_ffr. > > Not right now but I do expect to build on this in the not too distant > future. OK, but due to the fact that we need to dirty a P-register in order to zero the FFR, these still don't feel like independent operations. Can we control the clearing of the FFR (or not) with an argument to a combined macro? Cheers ---Dave _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel