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[155.137.199.74]) by smtp.gmail.com with ESMTPSA id g10-20020a170902868a00b0016cf3f124e1sm10595963plo.234.2022.10.05.09.43.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 05 Oct 2022 09:43:36 -0700 (PDT) Message-ID: Date: Thu, 6 Oct 2022 00:43:31 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.3.0 Subject: Re: [PATCH v3 2/2] irqchip/apple-aic: Add support for A7-A11 SoCs Content-Language: en-US To: Sven Peter , Konrad Dybcio , asahi@lists.linux.dev, linux-arm-kernel@lists.infradead.org Cc: Hector Martin , Alyssa Rosenzweig , Thomas Gleixner , Marc Zyngier , Rob Herring , Krzysztof Kozlowski , linux-kernel@vger.kernel.org, devicetree@vger.kernel.org References: <20221004112724.31621-1-konrad.dybcio@somainline.org> <20221004112724.31621-2-konrad.dybcio@somainline.org> <3398859f-e872-4f1d-8a03-4dcb1e46e010@app.fastmail.com> From: Nick Chan In-Reply-To: <3398859f-e872-4f1d-8a03-4dcb1e46e010@app.fastmail.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20221005_094340_877716_431E8944 X-CRM114-Status: GOOD ( 27.15 ) 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-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 4/10/2022 23:56, Sven Peter wrote: > Hi, > > > On Tue, Oct 4, 2022, at 13:27, Konrad Dybcio wrote: >> Add support for A7-A11 SoCs by if-ing out some features only present >> on: >> >> * A11 & newer (implementation-defined IPI & UNCORE registers) >> * A11[1] & newer (fast IPI support). >> >> UNCORE/UNCORE2 and IPI registers conveniently both first appeared on >> A11, so introduce just one check for that. >> >> Knowing whether the SoC supports the latter is necessary, as they are >> written to, even if fast IPI is disabled. > > AFAIK that's only an artifact in this driver: It was added to prevent an FIQ > storm in case there were pending fast ipis (i.e. the bootloader was broken ;)) > when this driver didn't support fast ipis yet. > >> This in turn causes a crash >> on older platforms, as the implemention-defined registers either do >> something else or are not supposed to be touched - definitely not a >> NOP though. >> >> [1] A11 is supposed to use this feature, but it currently doesn't work >> for reasons unknown and hence remains disabled. It can easily be enabled >> on A11 only, as there is a SoC-specific compatible in the DT with a >> fallback to apple,aic. That said, it is not yet necessary, especially >> with only one core up, and it has worked a-ok so far. > > Just to make sure I understand this correctly - we have the following three situations: > > - base: no fastipi, no uncore, will work on A11 and M1 though > - A11: fastipi and uncore but fastipi is broken (possibly due to HW errata or some bug in this driver that only happens on A11) > - M1 (or maybe even A12 already, doesn't matter though): fastipi and uncore support > > If we figured out _why_ fastipi is broken on A11 we would only need a single > feature flag to enable both uncore and fastipi but for now we need two to > disable fastipi for A11 The previous issues with fast IPI does not seem to be reproducible with thisversion of patches anymore, at least when modifying the device tree to useapple,t8103-aic the device still boots. Tested on iPhone X. > > I'm also curious: What are the symptoms when you enable fastipi on A11? > > > Sven Nick Chan _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel