From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1B9D49461 for ; Thu, 21 Sep 2023 10:11:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 94BADC3278E; Thu, 21 Sep 2023 10:11:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1695291104; bh=AdutLBV21eG6/I5c7ck2kz5+kkufzxzMbnOhofwlRNc=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=FWi/MotY0IkufMUjM3uKZhdm+J7+OHxVMKxpp9S4ULn+0QBoAqNetS57FJt/Z82Jj O4jZOEpZ3K3DMsxVN+AsCK9an9VanRO9LUCPf2MBL+cJpjENamWN9SyImsDiZcXI9M m/tL9UhfOGgSLpLh2gRs6oovaNH1q5HV9y/R/oWLEwq2s5zLxtdLlG9agn0VqQhJiG 4zdLRFTvjZau67sD0cWB/t3ORDx8iPIqHJOL3U47iHQx+k5Fv7q0/+lvXkWbeAnYgD B8+L/gxKzFZDKtMqiOqOSatrbOTGqf6csrNnPMWYgsj50Ls9fgs4iFIk4auWYhyVOr x+I/nBQXLndPw== Date: Thu, 21 Sep 2023 12:11:39 +0200 From: Lorenzo Pieralisi To: Marc Zyngier Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, devicetree@vger.kernel.org, Mark Rutland , Robin Murphy , Rob Herring , Fang Xiang Subject: Re: [PATCH v2 0/2] irqchip/gic-v3: Enable non-coherent GIC designs probing Message-ID: References: <20230905104721.52199-1-lpieralisi@kernel.org> <20230906094139.16032-1-lpieralisi@kernel.org> <6f94c6d38f00031bf7c59e0cb8baf04c@kernel.org> Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Wed, Sep 06, 2023 at 01:23:30PM +0200, Lorenzo Pieralisi wrote: > On Wed, Sep 06, 2023 at 10:52:01AM +0100, Marc Zyngier wrote: > > On 2023-09-06 10:41, Lorenzo Pieralisi wrote: > > > This series is v2 of a previous version[1]. > > > > > > v1 -> v2: > > > - Updated DT bindings as per feedback > > > - Updated patch[2] to use GIC quirks infrastructure > > > > > > [1] > > > https://lore.kernel.org/all/20230905104721.52199-1-lpieralisi@kernel.org > > > > > > Original cover letter > > > --- > > > The GICv3 architecture specifications provide a means for the > > > system programmer to set the shareability and cacheability > > > attributes the GIC components (redistributors and ITSes) use > > > to drive memory transactions. > > > > > > Albeit the architecture give control over shareability/cacheability > > > memory transactions attributes (and barriers), it is allowed to > > > connect the GIC interconnect ports to non-coherent memory ports > > > on the interconnect, basically tying off shareability/cacheability > > > "wires" and de-facto making the redistributors and ITSes non-coherent > > > memory observers. > > > > > > This series aims at starting a discussion over a possible solution > > > to this problem, by adding to the GIC device tree bindings the > > > standard dma-noncoherent property. The GIC driver uses the property > > > to force the redistributors and ITSes shareability attributes to > > > non-shareable, which consequently forces the driver to use CMOs > > > on GIC memory tables. > > > > > > On ARM DT DMA is default non-coherent, so the GIC driver can't rely > > > on the generic DT dma-coherent/non-coherent property management layer > > > (of_dma_is_coherent()) which would default all GIC designs in the field > > > as non-coherent; it has to rely on ad-hoc dma-noncoherent property > > > handling. > > > > > > When a consistent approach is agreed upon for DT an equivalent binding > > > will > > > be put forward for ACPI based systems. > > > > What is the plan for this last point? I'd like to see at least > > a proposal before taking this series in. > > Absolutely, I am starting a thread on related MADT changes, should not > take too long. Quick update, bindings filed, I will code against it but we should not merge anything till it is approved (could be missing v6.7 timeline). https://bugzilla.tianocore.org/show_bug.cgi?id=4557 Lorenzo