From patchwork Mon Feb 27 16:12:18 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Thomas Petazzoni X-Patchwork-Id: 9593545 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 04C3E60471 for ; Mon, 27 Feb 2017 16:15:34 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id EA53928487 for ; Mon, 27 Feb 2017 16:15:33 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id DF27A2848D; Mon, 27 Feb 2017 16:15:33 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.9 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID autolearn=ham version=3.3.1 Received: from bombadil.infradead.org (bombadil.infradead.org [65.50.211.133]) (using TLSv1.2 with cipher AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.wl.linuxfoundation.org (Postfix) with ESMTPS id 66BD428487 for ; Mon, 27 Feb 2017 16:15:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:MIME-Version:Cc:List-Subscribe: List-Help:List-Post:List-Archive:List-Unsubscribe:List-Id:References: In-Reply-To:Message-Id:Date:Subject:To:From:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=9PepGMNl4hMNx3XljyNImpQxCmtCnypFkeg9BsEJ0qs=; b=hKHHbP/sxjkMzvbRGnbD9QDOdz N8SIk8lPWtkVRe3Tb+VpWG098FH6WzThZ3MHklXelMQiAOVUFMv3Ar49KPR7DVywPB552PRkxIFiH TpgPzNV/LfEtt+sVf67lkk2j2nMSewT7Ks2Qygr99UwkCieCarjbXeAxt0Xn3s06pPD5bL9pwYdN/ IjQAV41BXb+NWzNk/Tc9s+KnUDJHKGTjufJiAabNaMH07lMKgFdpCwOSCOsRaONKtESEbpf5FlybK 81u2T27uJsZuep+tOTlCWtYzquXkl34ddFCdW3fcI9vTBpFOiz8L9oy9ScGjB/8SbYEF3P5zGowZe ivBJr7uA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.87 #1 (Red Hat Linux)) id 1ciNxQ-0000s9-Vl; Mon, 27 Feb 2017 16:15:29 +0000 Received: from mail.free-electrons.com ([62.4.15.54]) by bombadil.infradead.org with esmtp (Exim 4.87 #1 (Red Hat Linux)) id 1ciNv4-0006Is-Ii for linux-arm-kernel@lists.infradead.org; Mon, 27 Feb 2017 16:13:07 +0000 Received: by mail.free-electrons.com (Postfix, from userid 110) id 0F7FE206E8; Mon, 27 Feb 2017 17:12:40 +0100 (CET) Received: from localhost (LStLambert-657-1-97-87.w90-63.abo.wanadoo.fr [90.63.216.87]) by mail.free-electrons.com (Postfix) with ESMTPSA id DCD89206ED; Mon, 27 Feb 2017 17:12:29 +0100 (CET) From: Thomas Petazzoni To: Thomas Gleixner , Jason Cooper , Marc Zyngier Subject: [PATCH v2 2/4] irqchip: armada-370-xp: document the overall driver logic Date: Mon, 27 Feb 2017 17:12:18 +0100 Message-Id: <1488211940-26489-3-git-send-email-thomas.petazzoni@free-electrons.com> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1488211940-26489-1-git-send-email-thomas.petazzoni@free-electrons.com> References: <1488211940-26489-1-git-send-email-thomas.petazzoni@free-electrons.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20170227_081303_029110_F39C55F1 X-CRM114-Status: GOOD ( 16.40 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Thomas Petazzoni , Andrew Lunn , Yehuda Yitschak , Hanna Hawa , Nadav Haklai , Gregory Clement , linux-arm-kernel@lists.infradead.org, Sebastian Hesselbarth MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Virus-Scanned: ClamAV using ClamSMTP Since the overall logic of the driver to handle the global and per-CPU masking of the interrupts is far from trivial, this commit adds a long comment detailing how the hardware operates and what strategy the driver implements on top of that. Signed-off-by: Thomas Petazzoni Acked-by: Gregory CLEMENT --- drivers/irqchip/irq-armada-370-xp.c | 80 +++++++++++++++++++++++++++++++++++++ 1 file changed, 80 insertions(+) diff --git a/drivers/irqchip/irq-armada-370-xp.c b/drivers/irqchip/irq-armada-370-xp.c index 76147df..1f7dea6 100644 --- a/drivers/irqchip/irq-armada-370-xp.c +++ b/drivers/irqchip/irq-armada-370-xp.c @@ -34,6 +34,86 @@ #include #include +/* + * Overall diagram of the Armada XP interrupt controller: + * + * To CPU 0 To CPU 1 + * + * /\ /\ + * || || + * +---------------+ +---------------+ + * | | | | + * | per-CPU | | per-CPU | + * | mask/unmask | | mask/unmask | + * | CPU0 | | CPU1 | + * | | | | + * +---------------+ +---------------+ + * /\ /\ + * || || + * \\_______________________// + * || + * +-------------------+ + * | | + * | Global interrupt | + * | mask/unmask | + * | | + * +-------------------+ + * /\ + * || + * interrupt from + * device + * + * The "global interrupt mask/unmask" is modified using the + * ARMADA_370_XP_INT_SET_ENABLE_OFFS and + * ARMADA_370_XP_INT_CLEAR_ENABLE_OFFS registers, which are relative + * to "main_int_base". + * + * The "per-CPU mask/unmask" is modified using the + * ARMADA_370_XP_INT_SET_MASK_OFFS and + * ARMADA_370_XP_INT_CLEAR_MASK_OFFS registers, which are relative to + * "per_cpu_int_base". This base address points to a special address, + * which automatically accesses the registers of the current CPU. + * + * The per-CPU mask/unmask can also be adjusted using the global + * per-interrupt ARMADA_370_XP_INT_SOURCE_CTL register, which we use + * to configure interrupt affinity. + * + * Due to this model, all interrupts need to be mask/unmasked at two + * different levels: at the global level and at the per-CPU level. + * + * This driver takes the following approach to deal with this: + * + * - For global interrupts: + * + * At ->map() time, a global interrupt is unmasked at the per-CPU + * mask/unmask level. It is therefore unmasked at this level for + * the current CPU, running the ->map() code. This allows to have + * the interrupt unmasked at this level in non-SMP + * configurations. In SMP configurations, the ->set_affinity() + * callback is called, which using the + * ARMADA_370_XP_INT_SOURCE_CTL() readjusts the per-CPU mask/unmask + * for the interrupt. + * + * The ->mask() and ->unmask() operations only mask/unmask the + * interrupt at the "global" level. + * + * So, a global interrupt is enabled at the per-CPU level as soon + * as it is mapped. At run time, the masking/unmasking takes place + * at the global level. + * + * - For per-CPU interrupts + * + * At ->map() time, a per-CPU interrupt is unmasked at the global + * mask/unmask level. + * + * The ->mask() and ->unmask() operations mask/unmask the interrupt + * at the per-CPU level. + * + * So, a per-CPU interrupt is enabled at the global level as soon + * as it is mapped. At run time, the masking/unmasking takes place + * at the per-CPU level. + */ + /* Registers relative to main_int_base */ #define ARMADA_370_XP_INT_CONTROL (0x00) #define ARMADA_370_XP_SW_TRIG_INT_OFFS (0x04)