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 EA80BC49ED7 for ; Fri, 13 Sep 2019 10:33:02 +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 BDAE6208C0 for ; Fri, 13 Sep 2019 10:33:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="X9C31efi" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BDAE6208C0 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-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=FeARvQuOZVwWHqqq6SShjVx99k+iitkhU6qkDA8gUM0=; b=X9C31efi/kcI3y 9yGAkcoGu+99n3xL3CrKBDbBQ6MYIHMh84aODlgVtUfreMlqDq0u1P2sYc6psghhj/h6+hCUroLIg QI0PQQk8d9G9UXUUQkk03isUHvv6PfqLRghmkzeB1ngFryc8+7ckbIeg7dDQQoPOs1GxB8+Rz5Zyy 1cuJrm1ATw+OfVhMIjZaVT19MEwQTYKet4Ass3V9U5fOCw8VvBTCnZoNz1U7oQ+FPPCE27TRh6sdF XsR/JIEq0aKMmpPsvhnVYGJCd+oQeuzenWWdp/HxLQTNzhRPyIKkuoGrPT3EOLMPcYbwNBDjSUcYK 1UjksjgVo3UF6su0irgQ==; 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 1i8ist-00088n-3Y; Fri, 13 Sep 2019 10:32:59 +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 1i8isp-00088U-VG for linux-arm-kernel@lists.infradead.org; Fri, 13 Sep 2019 10:32:57 +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 614E928; Fri, 13 Sep 2019 03:32:55 -0700 (PDT) Received: from localhost (unknown [10.37.6.20]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CB3613F59C; Fri, 13 Sep 2019 03:32:54 -0700 (PDT) Date: Fri, 13 Sep 2019 11:32:53 +0100 From: Andrew Murray To: Suzuki K Poulose Subject: Re: [PATCH v5 3/3] coresight: etm4x: save/restore state for external agents Message-ID: <20190913103252.GL9720@e119886-lin.cambridge.arm.com> References: <20190816154615.39854-1-andrew.murray@arm.com> <20190816154615.39854-4-andrew.murray@arm.com> <4b34efe9-7266-30b6-6a8a-8a85bacfe5a3@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <4b34efe9-7266-30b6-6a8a-8a85bacfe5a3@arm.com> User-Agent: Mutt/1.10.1+81 (426a6c1) (2018-08-26) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190913_033256_054301_57776B8F X-CRM114-Status: GOOD ( 31.08 ) 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, mathieu.poirier@linaro.org, alexander.shishkin@linux.intel.com, coresight@lists.linaro.org, leo.yan@linaro.org, Sudeep.Holla@arm.com, linux-arm-kernel@lists.infradead.org, mike.leach@linaro.org 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 Thu, Sep 12, 2019 at 04:35:20PM +0100, Suzuki K Poulose wrote: > 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 ? > Yes I think this is OK. > > 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 ? I'll change it to ... 3 = self-hosted/external (keeps power on)"); > > > /* 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. Good idea. I'll modify it slightly however. > > > 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. OK. Thanks, Andrew Murray > > Kind regards > Suzuki _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel