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Received: from mout-p-201.mailbox.org ([2001:67c:2050:0:465::201]) by desiato.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wNVRe-00000002u7r-2wjb for linux-arm-kernel@lists.infradead.org; Thu, 14 May 2026 12:45:45 +0000 Received: from smtp2.mailbox.org (smtp2.mailbox.org [10.196.197.2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mout-p-201.mailbox.org (Postfix) with ESMTPS id 4gGVRj1mYbz9v8n; Thu, 14 May 2026 14:45:37 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mailbox.org; s=mail20150812; t=1778762737; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=g0meuM2dktCGP0Ls8RIINE+UeHLH/T7v1m7onF+s9Lw=; b=X0gHDrKhxCF5P/S4fvZMjURB8scyGQPD6vgQH1LSOYcaVs0C6y8eR5jEz4ayx0eidhSlqo ZbUQQfm1ro4j1scJaCrqedXSe50WOM6fvlJiFjmxANS2zY8mUXJWy5Ozge3SnOW0j6It/Q FJQUHiDVFpWxUixizV21HEkIpIh+G8sByKSw3J09xaHsi/1itxZzULmA/s6CqCU9c+7tHd IO7zl/Y+6RKYD5uTQMLb/CZ3MwLsxdfnuLvPtc8B0NxA08z8JrChbZcDYAA9txf5Ug8MUc QwNgXHqZqC1fepxEbWT1V01HFGv31mOfbXsTkKuEldmgeBhWAJ5grhBPfucIcA== Message-ID: <32ace62d-2faf-4197-a548-93111b2a68ea@mailbox.org> Date: Thu, 14 May 2026 14:45:21 +0200 MIME-Version: 1.0 Subject: Re: [PATCH] arm64: dts: renesas: r8a78000: Fix GIC-720AE View 1 Redistributor description To: Marc Zyngier Cc: linux-arm-kernel@lists.infradead.org, Conor Dooley , Geert Uytterhoeven , Krzysztof Kozlowski , Kuninori Morimoto , Magnus Damm , Rob Herring , devicetree@vger.kernel.org, linux-renesas-soc@vger.kernel.org References: <20260513223125.43337-1-marek.vasut+renesas@mailbox.org> <86bjeixyi1.wl-maz@kernel.org> Content-Language: en-US From: Marek Vasut In-Reply-To: <86bjeixyi1.wl-maz@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-MBO-RS-META: 68hnufgn5133ui5p9dmagwrtyamem9zr X-MBO-RS-ID: 8326ad8e9f3d17f6c68 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260514_134543_207651_FFFD3B75 X-CRM114-Status: GOOD ( 27.67 ) 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: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 5/14/26 9:04 AM, Marc Zyngier wrote: > On Wed, 13 May 2026 23:30:08 +0100, > Marek Vasut wrote: >> >> The Renesas R-Car X5H (R8A78000) SoC contains Arm CoreLink GIC-720AE >> Generic Interrupt Controller with Multi View capability. Firmware has >> access to configuration View 0, Linux kernel has access to View 1. > > Huh. That's pretty unexpected. The usual wisdom is to give the APs > view 0 so that it looks like a "normal" machine, rather than only a > partition of the system (which is what view != 0 indicates). > > I guess there is some additional fun going on there, such as other > CPUs getting a portion of the GIC for themselves, and firmware > preventing whatever is running on the APs to interact with them... This is my understanding as well, partitioning of the system is an intended use case. On the development hardware I have access to, no partitioning is applied, all cores are available to Linux. >> The Arm CoreLink GIC-720AE Generic Interrupt Controller Technical >> Reference Manual, currently latest r2p1 [1], chapter "Programmers model >> for GIC-720AE", subchapter "Redistributor registers for control and >> physical LPIs summary", part "GICR_TYPER, Redistributor Type Register" >> clarifies register "GICR_TYPER" bit 4 "Last" behavior in Multi View >> setup as follows: >> >> " >> Last >> Last Redistributor: >> >> 0 ... This Redistributor is not the last Redistributor on the chip. >> 1 ... This Redistributor is the last Redistributor on the chip. >> When GICD_CFGID.VIEW == 1, for views 1, 2, or 3 this bit >> always returns 1. >> " >> >> On this SoC, GICD_CFGID.VIEW is 1 and the Linux kernel has access to >> View 1, therefore Linux kernel GICv3 driver will interpret register >> "GICR_TYPER" bit 4 "Last" = 1 in the first Redistributor in continuous >> Redistributor page as that first Redistributor being the one and only >> Redistributor and will stop processing the continuous Redistributor >> page further. This will prevent the other Redistributors from being >> recognized by the system and used for other PEs. >> >> Because the hardware indicates that the continuous Redistributor page >> is not continuous for View 1, 2, or 3, describe every Redistributor >> separately in the DT. This makes all Redistributors for all cores >> accessible in Linux. >> >> [1] https://developer.arm.com/documentation/102666/0201/Programmers-model-for-GIC-720AE/Redistributor-registers-for-control-and-physical-LPIs-summary/GICR-TYPER--Redistributor-Type-Register?lang=en >> > > I am amazed that you managed to find anything at all on this web site. > > I would refrain from adding links to any ARM web sites in a commit > message though. They tend to have a 10 minutes half-life period, and > whole specs to disappear from public view when they are not flavour of > the week anymore. > > A link to the equivalent PDF has better chances to survive further > creative^WAI slop driven reorg of the documentation: > > https://documentation-service.arm.com/static/69ef3c1cd35efd294e335c43 > > but your best bet is to download it, archive it, and refer to it > yourself. Thank you for that. That is the one thing I did not manage to find on that website, a PDF of the GIC-720AE manual. I will include that link in a V2. >> Fixes: 63500d12cf76 ("arm64: dts: renesas: Add R8A78000 SoC support") >> Signed-off-by: Marek Vasut > > Acked-by: Marc Zyngier > > M. > -- Best regards, Marek Vasut