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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 1htUze-0006Eg-Ix; Fri, 02 Aug 2019 10:41:02 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1htUzZ-0006E7-Oo for linux-arm-kernel@lists.infradead.org; Fri, 02 Aug 2019 10:41:00 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id C9AA7344; Fri, 2 Aug 2019 03:40:56 -0700 (PDT) Received: from dawn-kernel.cambridge.arm.com (unknown [10.1.197.116]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 957C33F71F; Fri, 2 Aug 2019 03:40:55 -0700 (PDT) Subject: Re: [PATCH v4 6/6] dt-bindings: arm: coresight: Add support for coresight-needs-save-restore To: andrew.murray@arm.com, mathieu.poirier@linaro.org, alexander.shishkin@linux.intel.com References: <20190730125157.884-1-andrew.murray@arm.com> <20190730125157.884-7-andrew.murray@arm.com> From: Suzuki K Poulose Message-ID: <9df0eea2-a9bd-3a93-ca51-9c3d2391a1cf@arm.com> Date: Fri, 2 Aug 2019 11:40:54 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190730125157.884-7-andrew.murray@arm.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190802_034058_347154_9BA10FE8 X-CRM114-Status: GOOD ( 19.21 ) 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@arm.com, coresight@lists.linaro.org, leo.yan@linaro.org, Sudeep.Holla@arm.com, linux-arm-kernel@lists.infradead.org, mike.leach@linaro.org Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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." Cheers Suzuki _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel