From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 787FFC433FF for ; Sun, 4 Aug 2019 13:14:07 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 44DF3206A2 for ; Sun, 4 Aug 2019 13:14:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="oT+YnSh2"; dkim=fail reason="signature verification failed" (2048-bit key) header.d=linaro.org header.i=@linaro.org header.b="geWo14fY" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 44DF3206A2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linaro.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:To:Subject:Message-ID:Date:From: In-Reply-To:References:MIME-Version:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=ojO2PunuCmIu8vSXiGTk2l7S8zmLKShBCkb815yMP0A=; b=oT+YnSh2VvsHrq /93+LoLjIBjxUUkXZ+aLg+fT8ems2zyohaxrIbIOkEOBl7T3AUi9FRqDIBjJETOTrNXD3L4QSOkLh NZkrGLhwgABXaMFRhTIu1x8lROg/qPrwHp8jLBKTV9WcW2epA6pdmBJVtDvzKf1fWzEIorGrZii6G iVK0b8pChX174juh4M6v2AqZZa3qHuAWdtTgm3Ty9hQshjk4+hC7Ql5owEqQBbJt7ibbQ+1z5qcWi 3m13Y6oJfpCLMVPGIU5TeQKOKD1c/xparuFzaBZARaFcA8XjPsuUjqo4KcXZ4iGZs8saGJ01nrTaQ u6qJBbyBBdUx76HQQRbw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1huGKs-00020N-0C; Sun, 04 Aug 2019 13:14:06 +0000 Received: from mail-io1-xd42.google.com ([2607:f8b0:4864:20::d42]) by bombadil.infradead.org with esmtps (Exim 4.92 #3 (Red Hat Linux)) id 1huGKn-0001zz-LB for linux-arm-kernel@lists.infradead.org; Sun, 04 Aug 2019 13:14:03 +0000 Received: by mail-io1-xd42.google.com with SMTP id e20so29019397iob.9 for ; Sun, 04 Aug 2019 06:13:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=saSzK0dvs8XEQEZsxQgLsa/jfT6Yv+ibyJWmYYiklBA=; b=geWo14fYYllSOneTLqBErKdiK7ERvlPHlGjC5CNhd6ZItZ3k1kvp9ngEW3u2vRPtJ3 WGw0T6+kiq/5R5+EMVVd1z4wufIgBazGDkBBA3TOHEQrzefWR7V26gGXLbBDiXbLUueA xHPNBnHwqsR4XMpW8becJW8W2U34CjdumRkC5/4zZRbR6VPk7TwTcsliTW2arblMWQpP AeWTGZ6xByGTSp9lyPlnzC1ox/S0C10Si50FsY0bzU9oPHTsfLP69X5D/AFyqgyv4UW9 WLSWa41/Mrfk17ceIOF0nJA7gO0g3OwPCteypTAx8Ns+1a+AXWAWUeviQD+HCLewGQxX D3rw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=saSzK0dvs8XEQEZsxQgLsa/jfT6Yv+ibyJWmYYiklBA=; b=CH5isRVkS+UW+pTMS7NOGZeYWz4x0AKEMI9ARE7sbvkLPIeehUQeCye4aYBvDoHM+E z0vrrKJPbVujcDzAAj5jUAPDqAqsPHkWeyGCv2Vy/hBRtLgK/7t8+uVy1XqFYrVTEKRn FhR/D52/ItCloPaUnKUTo7TFq0kYtTS9iUSRPHGxGoop8oL8PwJa34Al19yfL+8+QhB5 7Dm9DL5zX5INO1dBEPBV0M7j1XspVhD5rO/Wi+XNTKZbekdb2kt/dOvNNDvQZF7tte2i 8ufYD37/0YP4w9flhTQbLFKVyfPsiZ0fl12VvsqL55GrY3fIoXgYmhSBCS+gW/14x8TT 8BPA== X-Gm-Message-State: APjAAAVi3CLLUmKeRHBdsvBn2rsmQH4hfAzxWNzw46ov6D8N4tNf7p71 OCMNJRvCfgffDPRrMki1uK2CUYNCfVZtXPoSMNygIw== X-Google-Smtp-Source: APXvYqzEYr77iikFeNno1hrmPbqZg/KxGzo98SGm01ZcJJlHumIfe99EUO6Oekdfe3TQ4CmxpvBw9XwRjdjCCaw+WYs= X-Received: by 2002:a5d:9dc7:: with SMTP id 7mr980416ioo.237.1564924437341; Sun, 04 Aug 2019 06:13:57 -0700 (PDT) MIME-Version: 1.0 References: <20190730125157.884-1-andrew.murray@arm.com> <20190730125157.884-7-andrew.murray@arm.com> <9df0eea2-a9bd-3a93-ca51-9c3d2391a1cf@arm.com> <20190802143751.GP56241@e119886-lin.cambridge.arm.com> In-Reply-To: <20190802143751.GP56241@e119886-lin.cambridge.arm.com> From: Mathieu Poirier Date: Sun, 4 Aug 2019 07:13:45 -0600 Message-ID: Subject: Re: [PATCH v4 6/6] dt-bindings: arm: coresight: Add support for coresight-needs-save-restore To: Andrew Murray X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190804_061401_724789_EC688868 X-CRM114-Status: GOOD ( 25.52 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Al Grant , Suzuki K Poulose , Alexander Shishkin , Coresight ML , Sudeep Holla , Leo Yan , linux-arm-kernel , Mike Leach Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Fri, 2 Aug 2019 at 08:37, Andrew Murray wrote: > > On Fri, Aug 02, 2019 at 11:40:54AM +0100, Suzuki K Poulose wrote: > > Hi Andrew, > > > > On 30/07/2019 13:51, Andrew Murray wrote: > > > Some coresight components, because of choices made during hardware > > > integration, require their state to be saved and restored across CPU low > > > power states. > > > > > > The software has no reliable method of detecting when save/restore is > > > required thus let's add a binding to inform the kernel. > > > > > > Signed-off-by: Andrew Murray > > > --- > > > Documentation/devicetree/bindings/arm/coresight.txt | 3 +++ > > > 1 file changed, 3 insertions(+) > > > > > > diff --git a/Documentation/devicetree/bindings/arm/coresight.txt b/Documentation/devicetree/bindings/arm/coresight.txt > > > index fcc3bacfd8bc..7cbdb7893af8 100644 > > > --- a/Documentation/devicetree/bindings/arm/coresight.txt > > > +++ b/Documentation/devicetree/bindings/arm/coresight.txt > > > @@ -92,6 +92,9 @@ its hardware characteristcs. > > > * arm,cp14: must be present if the system accesses ETM/PTM management > > > registers via co-processor 14. > > > + * arm,coresight-needs-save-restore: boolean. Indicates that software > > > + should save/restore state across power down. > > > + > > > > Do you think we could be a bit more descriptive here about when people could add > > it to the DT ? Here we don't mention when someone should use this property and > > it may be added to platforms where it may be absolutely unnecessary. How about : > > > > "Indicates that the hardware implementation may not honor the Powerup request > > from the software and thus might loose the register context on CPU power > > down (e.g, during CPUIdle). Software must save/restore the context during a > > CPU power transition cycle." > > How about the following: > > "Indicates that the hardware will loose register context on CPU power down (e.g. > CPUIdle), despite the TRCPDCR.PU bit being set." > > I'm keen to avoid making suggestions about what the kernel will do when it sees > this flag and thus prefer to focus on describing what the hardware does. So I > dropped your last sentence. However the name of the flag still implies policy > which I don't like. > > I also changed the 'may not honor' wording, I'm not sure if this is really the > case or if the spec is open to interpretation. > > It would great for this wording to also apply to other CS components though I > haven't investigated if these have a PU bit or something different. Exactly - the definition needs to be broad enough to apply to other CS components. Mike what do you think would be appropriate for CTIs? > > Thanks, > > Andrew Murray > > > > > Cheers > > Suzuki _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel