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=-8.5 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,USER_AGENT_SANE_1 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 E6D51C4CEC5 for ; Thu, 12 Sep 2019 15:37:24 +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 BAAE720578 for ; Thu, 12 Sep 2019 15:37:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="uEMJFDP7" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BAAE720578 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.com 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-Type: Content-Transfer-Encoding:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date:Message-ID:From: References:To:Subject:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=X7LbfQxqKV+LGbNXW+fIoa8CwMBqdhuxklozVyGzyxM=; b=uEMJFDP7bWdum+psVzSf7qAV7 exN31QK1u3d71a+b+bXbCnwjYlHE5utp+++Ycp3hR40kHeC0PUcc82fWK4UlBr0QW7hnBiv2bhaPy G1liQ+iwoYD5wAzO8aQdWU/UZetawJs/oghpfJNRCSZ6YR3Zv5ayOuz0gEXBRawUbxnw4qdPlnQxF hHQ4PYsk5/k8RW+397mrWT6ibgwG4wk5ybt6LMwrJCtJRnY1J7vr4B88xKy7ct6jX2ZIyh+ftvpPu WldeE0MqRWC9xYQGPhWnj3HACypvZYTYM9r14GxKTbfp2Wu11uznR25Krn7jWcdTCbw2ry8sw/Vks XBRN42n/g==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.2 #3 (Red Hat Linux)) id 1i8R9q-0002yB-O9; Thu, 12 Sep 2019 15:37:18 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.2 #3 (Red Hat Linux)) id 1i8R80-0001NI-FI for linux-arm-kernel@lists.infradead.org; Thu, 12 Sep 2019 15:35:27 +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 94A8E337; Thu, 12 Sep 2019 08:35:22 -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 75BB73F71F; Thu, 12 Sep 2019 08:35:21 -0700 (PDT) Subject: Re: [PATCH v5 3/3] coresight: etm4x: save/restore state for external agents To: andrew.murray@arm.com, mathieu.poirier@linaro.org, alexander.shishkin@linux.intel.com References: <20190816154615.39854-1-andrew.murray@arm.com> <20190816154615.39854-4-andrew.murray@arm.com> From: Suzuki K Poulose Message-ID: <4b34efe9-7266-30b6-6a8a-8a85bacfe5a3@arm.com> Date: Thu, 12 Sep 2019 16:35:20 +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: <20190816154615.39854-4-andrew.murray@arm.com> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190912_083525_172377_1287FD75 X-CRM114-Status: GOOD ( 30.58 ) 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 16/08/2019 16:46, Andrew Murray wrote: > Some hardware will ignore bit TRCPDCR.PU which is used to signal > to hardware that power should not be removed from the trace unit. Much like > self-hosted debug, we should also save/restore the trace unit state when > it is in use by external agents. > > We wish to avoid saving the hardware state when coresight isn't in use > to reduce PM latency - However as external trace/debug is designed to be > unintrusive to the CPU, the only way of determining that an external agent is > present is to read the claim tags (TRCCLAIMCLR). Unfortunately this register > needs power and clocking - something it won't have when coresight isn't in use. > We also don't want to temporarily enable it due to the latency and PM context. > > Let's compromise by adding a module parameter that will keep the trace unit > powered and clocked, thus allowing us to only save/restore state when external > trace (or self-hosted) is in use. Though please note that this doesn't allow > for tracing from boot on hardware that needs save/restore as the CPU may idle > prior to the ETMv4 driver starting and adding PM hooks to save/restore. > This looks fine to me. Some minor comments below. > Signed-off-by: Andrew Murray > --- > drivers/hwtracing/coresight/coresight-etm4x.c | 27 ++++++++++++++++--- > drivers/hwtracing/coresight/coresight.c | 2 +- > include/linux/coresight.h | 7 +++++ > 3 files changed, 31 insertions(+), 5 deletions(-) > > diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c > index 35a524eec36d..c5d527f7cbd5 100644 > --- a/drivers/hwtracing/coresight/coresight-etm4x.c > +++ b/drivers/hwtracing/coresight/coresight-etm4x.c > @@ -42,11 +42,12 @@ MODULE_PARM_DESC(boot_enable, "Enable tracing on boot"); > #define PARAM_PM_SAVE_FIRMWARE 0 /* save self-hosted state as per firmware */ > #define PARAM_PM_SAVE_NEVER 1 /* never save any state */ > #define PARAM_PM_SAVE_SELF_HOSTED 2 /* save self-hosted state only */ > +#define PARAM_PM_SAVE_EXTERNAL 3 /* save all state (keeps power on) */ Should we say PARAM_PM_SAVE_ALWAYS instead ? > > static int pm_save_enable = PARAM_PM_SAVE_FIRMWARE; > module_param(pm_save_enable, int, 0444); > MODULE_PARM_DESC(pm_save_enable, > - "Save/restore state on power down: 1 = never, 2 = self-hosted"); > + "Save/restore state on power down: 1 = never, 2 = self-hosted, 3 = self-hosted/external"); similarly here and also mention that the power/clocks are not dropped in that case ? I see the comment above, but please could we make it more explicit ? > > /* The number of ETMv4 currently registered */ > static int etm4_count; > @@ -1331,6 +1332,22 @@ static void etm4_cpu_restore(struct etmv4_drvdata *drvdata) > CS_LOCK(drvdata->base); > } > > +static bool etm4_coresight_in_use(struct etmv4_drvdata *drvdata) > +{ > + /* Self-hosted session in progress? */ > + if (local_read(&drvdata->mode)) > + return true; > + > + /* External agents can be detected through claim tags however we > + * only read these tags if the trace unit is powered. > + */ > + if (drvdata->csdev && pm_runtime_active(drvdata->csdev->dev.parent)) > + if (coresight_is_claimed_any(drvdata->base)) > + return true; > + > + return false; > +} > + > static int etm4_cpu_pm_notify(struct notifier_block *nb, unsigned long cmd, > void *v) > { > @@ -1350,8 +1367,8 @@ static int etm4_cpu_pm_notify(struct notifier_block *nb, unsigned long cmd, > > switch (cmd) { > case CPU_PM_ENTER: > - /* save the state if self-hosted coresight is in use */ > - if (local_read(&drvdata->mode)) > + /* Save the state if coresight is in use */ > + if (etm4_coresight_in_use(drvdata)) > if (etm4_cpu_save(drvdata)) > return NOTIFY_BAD; > break; > @@ -1488,7 +1505,9 @@ static int etm4_probe(struct amba_device *adev, const struct amba_id *id) > goto err_arch_supported; > } > > - pm_runtime_put(&adev->dev); > + if (pm_save_enable != PARAM_PM_SAVE_EXTERNAL) > + pm_runtime_put(&adev->dev); > + It may be a good idea to explain why we don't drop the power here in a comment to help people reading the code. You could paste what is in the commit description in here to avoid another lookup. > dev_info(&drvdata->csdev->dev, "CPU%d: ETM v%d.%d initialized\n", > drvdata->cpu, drvdata->arch >> 4, drvdata->arch & 0xf); > > diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c > index e6ca899fea4e..474b7372864e 100644 > --- a/drivers/hwtracing/coresight/coresight.c > +++ b/drivers/hwtracing/coresight/coresight.c > @@ -140,7 +140,7 @@ static inline bool coresight_is_claimed_self_hosted(void __iomem *base) > return coresight_read_claim_tags(base) == CORESIGHT_CLAIM_SELF_HOSTED; > } > > -static inline bool coresight_is_claimed_any(void __iomem *base) > +bool coresight_is_claimed_any(void __iomem *base) > { > return coresight_read_claim_tags(base) != 0; > } minor nit: We may retain this as static inline and move this to the header file. Kind regards Suzuki _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel