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[78.11.189.27]) by smtp.gmail.com with ESMTPSA id dt6-20020a0565122a8600b004976809d6a7sm4553134lfb.283.2022.09.18.01.50.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 18 Sep 2022 01:51:11 -0700 (PDT) Message-ID: Date: Sun, 18 Sep 2022 09:50:58 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.13.0 Subject: Re: [PATCH] dt-bindings: timer: Add QEMU compatible strings Content-Language: en-US To: Marc Zyngier Cc: Jean-Philippe Brucker , mark.rutland@arm.com, robh+dt@kernel.org, krzysztof.kozlowski+dt@linaro.org, linux-kernel@vger.kernel.org, devicetree@vger.kernel.org References: <20220916132959.1910374-1-jean-philippe@linaro.org> <0acc2a21-27c2-ec85-0335-263d70c24469@linaro.org> <87mtaxltwm.wl-maz@kernel.org> From: Krzysztof Kozlowski In-Reply-To: <87mtaxltwm.wl-maz@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org On 17/09/2022 19:47, Marc Zyngier wrote: > On Sat, 17 Sep 2022 17:51:20 +0100, > Krzysztof Kozlowski wrote: >> >> On 16/09/2022 14:30, Jean-Philippe Brucker wrote: >>> QEMU uses both "arm,armv8-timer" and "arm,armv7-timer" as compatible >>> string. Although it is unlikely that any guest relies on this, we can't >>> be certain of that. Therefore, add these to the schema. Clean up the >>> compatible list a little while at it. >>> >>> Signed-off-by: Jean-Philippe Brucker >> >> I guess you wanted to say QEMU uses "arm,armv8-timer" followed by >> "arm,armv7-timer", because otherwise I would understand it that either >> that or that. Anyway, is it a valid (virtualized) hardware? Is ARMv8 >> timer really, really compatible with ARMv7 one? > > Yes. There isn't a shred of difference between the two in the earlier > revisions of the ARMv8 architecture, and none of the differences > introduced in later revisions are exposed to DT anyway. > >> I don't think we should document invalid setups out-of-tree, just >> because they are there, and something like this was also expressed by Rob: >> https://lore.kernel.org/all/20220518163255.GE3302100-robh@kernel.org/ > > This is, on the contrary, something that is perfectly valid. For > example, a system running a 32bit OS on a 64bit system is perfectly > entitled to expose both (v8 because that's what the HW is, v7 because > that's what the OS is the most likely to understand). > > You may find it odd, but that: > > - expresses something that is actually required > > - is what I, as the original author of this binding, have always > considered valid > > - has been valid for a long time (10+ years) before you decided it > suddenly wasn't > > I understand that the "DT police" has high standards, but this has > been around for much longer, and it isn't because the conversion to > schema is imperfect that you can rewrite history. > > As for the patch, I'd remove the QEMU reference and the deprecation. > This format is perfectly allowed, and is in use in most VMMs out > there. Yes, DT is an ABI. Thanks for the explanation, actually enough was to say that it is perfectly valid combination describing hardware. :) Acked-by: Krzysztof Kozlowski Best regards, Krzysztof