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[23.128.96.18]) by mx.google.com with ESMTP id qh17si3792177ejb.333.2020.11.12.05.11.31; Thu, 12 Nov 2020 05:11:53 -0800 (PST) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728251AbgKLNJi (ORCPT + 99 others); Thu, 12 Nov 2020 08:09:38 -0500 Received: from szxga07-in.huawei.com ([45.249.212.35]:7886 "EHLO szxga07-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727819AbgKLNJh (ORCPT ); Thu, 12 Nov 2020 08:09:37 -0500 Received: from DGGEMS412-HUB.china.huawei.com (unknown [172.30.72.58]) by szxga07-in.huawei.com (SkyGuard) with ESMTP id 4CX24M0YWMz75yr; Thu, 12 Nov 2020 21:09:23 +0800 (CST) Received: from [127.0.0.1] (10.65.95.32) by DGGEMS412-HUB.china.huawei.com (10.3.19.212) with Microsoft SMTP Server id 14.3.487.0; Thu, 12 Nov 2020 21:09:23 +0800 Subject: Re: [RFC PATCH v2] coresight: etm4x: Modify core-commit of cpu to avoid the overflow of HiSilicon ETM To: Mathieu Poirier References: <1597824397-29894-1-git-send-email-liuqi115@huawei.com> <20200827204426.GD22307@xps15> <548c973d-6964-ca5c-4c8d-fbc2386f3349@arm.com> <20200909162605.GB553266@xps15> <70f83c48-5a4e-5d4d-734f-105501d21a63@huawei.com> <20201111170345.GA3543438@xps15> CC: Mike Leach , Suzuki K Poulose , Greg Kroah-Hartman , linux-arm-kernel , "Linux Kernel Mailing List" , , Coresight ML From: Qi Liu Message-ID: <942b216e-9a17-7cc2-aedc-a2e003b00924@huawei.com> Date: Thu, 12 Nov 2020 21:09:16 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.7.1 MIME-Version: 1.0 In-Reply-To: <20201111170345.GA3543438@xps15> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.65.95.32] X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/11/12 1:03, Mathieu Poirier wrote: > On Wed, Nov 11, 2020 at 04:58:23PM +0800, Qi Liu wrote: >> Hi Mathieu, >> >> On 2020/9/10 0:26, Mathieu Poirier wrote: >>> On Wed, Sep 09, 2020 at 12:30:02PM +0100, Mike Leach wrote: >>>> Hi, >>>> >>>> On Wed, 2 Sep 2020 at 11:36, Suzuki K Poulose wrote: >>>>> On 08/27/2020 09:44 PM, Mathieu Poirier wrote: >>>>>> Hi Liu, >>>>>> >>>>>> On Wed, Aug 19, 2020 at 04:06:37PM +0800, Qi Liu wrote: >>>>>>> When too much trace information is generated on-chip, the ETM will >>>>>>> overflow, and cause data loss. This is a common phenomenon on ETM >>>>>>> devices. >>>>>>> >>>>>>> But sometimes we do not want to lose performance trace data, so we >>>>>>> suppress the speed of instructions sent from CPU core to ETM to >>>>>>> avoid the overflow of ETM. >>>>>>> >>>>>>> Signed-off-by: Qi Liu >>>>>>> --- >>>>>>> >>>>>>> Changes since v1: >>>>>>> - ETM on HiSilicon Hip09 platform supports backpressure, so does >>>>>>> not need to modify core commit. >>>>>>> >>>>>>> drivers/hwtracing/coresight/coresight-etm4x.c | 43 +++++++++++++++++++++++++++ >>>>>>> 1 file changed, 43 insertions(+) >>>>>>> >>>>>>> diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c >>>>>>> index 7797a57..7641f89 100644 >>>>>>> --- a/drivers/hwtracing/coresight/coresight-etm4x.c >>>>>>> +++ b/drivers/hwtracing/coresight/coresight-etm4x.c >>>>>>> @@ -43,6 +43,10 @@ MODULE_PARM_DESC(boot_enable, "Enable tracing on boot"); >>>>>>> #define PARAM_PM_SAVE_NEVER 1 /* never save any state */ >>>>>>> #define PARAM_PM_SAVE_SELF_HOSTED 2 /* save self-hosted state only */ >>>>>>> >>>>>>> +#define CORE_COMMIT_CLEAR 0x3000 >>>>>>> +#define CORE_COMMIT_SHIFT 12 >>>>>>> +#define HISI_ETM_AMBA_ID_V1 0x000b6d01 >>>>>>> + >>>>>>> static int pm_save_enable = PARAM_PM_SAVE_FIRMWARE; >>>>>>> module_param(pm_save_enable, int, 0444); >>>>>>> MODULE_PARM_DESC(pm_save_enable, >>>>>>> @@ -104,11 +108,40 @@ struct etm4_enable_arg { >>>>>>> int rc; >>>>>>> }; >>>>>>> >>>>>>> +static void etm4_cpu_actlr1_cfg(void *info) >>>>>>> +{ >>>>>>> + struct etm4_enable_arg *arg = (struct etm4_enable_arg *)info; >>>>>>> + u64 val; >>>>>>> + >>>>>>> + asm volatile("mrs %0,s3_1_c15_c2_5" : "=r"(val)); >>>>> >>>>> The ID register (S3_1_C15_c2_5) falls into implementation defined space. >>>>> See Arm ARM DDI 0487F.a, section "D12.3.2 Reserved encodings for >>>>> IMPLEMENTATION DEFINED registers". >>>>> >>>>> So, please stop calling this "etm4_cpu_actlr1_cfg". Since, >>>>> 1) actlr1 is not an architected name for the said encoding >>>>> 2) The id register could mean something else on another CPU. >>>>> >>>>> Rather this should indicate platform/CPU specific. e.g, >>>>> >>>>> etm4_cpu_hisilicon_config_core_commit() >>>>> >>>>> >>>>>>> + val &= ~CORE_COMMIT_CLEAR; >>>>>>> + val |= arg->rc << CORE_COMMIT_SHIFT; >>>>>>> + asm volatile("msr s3_1_c15_c2_5,%0" : : "r"(val)); >>>>>>> +} >>>>>>> + >>>>>>> +static void etm4_config_core_commit(int cpu, int val) >>>>>>> +{ >>>>>>> + struct etm4_enable_arg arg = {0}; >>>>>>> + >>>>>>> + arg.rc = val; >>>>>>> + smp_call_function_single(cpu, etm4_cpu_actlr1_cfg, &arg, 1); >>>>>> Function etm4_enable/disable_hw() are already running on the CPU they are >>>>>> supposed to so no need to call smp_call_function_single(). >>>>>> >>>>>>> +} >>>>>>> + >>>>>>> static int etm4_enable_hw(struct etmv4_drvdata *drvdata) >>>>>>> { >>>>>>> int i, rc; >>>>>>> + struct amba_device *adev; >>>>>>> struct etmv4_config *config = &drvdata->config; >>>>>>> struct device *etm_dev = &drvdata->csdev->dev; >>>>>>> + struct device *dev = drvdata->csdev->dev.parent; >>>>>>> + >>>>>>> + adev = container_of(dev, struct amba_device, dev); >>>>>>> + /* >>>>>>> + * If ETM device is HiSilicon ETM device, reduce the >>>>>>> + * core-commit to avoid ETM overflow. >>>>>>> + */ >>>>>>> + if (adev->periphid == HISI_ETM_AMBA_ID_V1) >>>>> Please could you move this check to the function above ? >>>>> Ideally, it would be good to have something like : >>>>> >>>>> etm4_config_impdef_features(); >>>>> >>>>> And : >>>>> >>>>> etm4_config_impdef_features(struct etm4_drvdata *drvdata) >>>>> { >>>>> etm4_cpu_hisilicon_config_core_commit(drvdata); >>>>> } >>>>> >>>> In addition to the above, Is it worth having this implementation >>>> defined code gated in the kernel configuration - like we do for core >>>> features sometimes? >>>> i,.e. >>>> CONFIG_ETM4X_IMPDEF_FEATURE (controls overall impdef support in the driver) >>>> and >>>> CONFIG_ETM4X_IMPDEF_HISILICON (depends on CONFIG_ETM4X_IMPDEF_FEATURE ) >>>> >>>> This way we keep non ETM architectural code off platforms that cannot >>>> use it / test it. >>>> >>> That's a good idea - they do the same for CPU erratas. >>> >> Considering that users sometimes use the same set of code on different platforms, how about >> using both CONFIG andperiphid to keep core-commit code off the platforms that do not >> need it? >> i, .e. >> CONFIG_ETM4X_IMPDEF_FEATURE ( controls overall impdef support in the driver ) >> periphid ( match impdef code with the target platform ) >> >> This way we could keep the same set of code working on different platforms, and it could help to >> ensure compatibility. > > I'm not 100% sure of what you mean by "same set of code working on different > platforms"... Up to know the way we have been handling peripheral IDs has > worked quite well and I don't intend on changing it unless there is a really > good reason. > Hi Mathieu, Perhaps I didn't make it clear and here is the code to express what I mean: #ifdef CONFIG_ETM4X_IMPDEF_FEATURE #define HISI_HIP08_AMBA_ID 0x000b6d01 #define HISI_HIP08_AMBA_MASK 0xfffff static void etm4_enable_arch_specific(struct etmv4_drvdata *drvdata) { struct device *dev = drvdata->csdev->dev.parent; struct amba_device *adev = container_of(dev, struct amba_device, dev); /* * If ETM device is HiSilicon ETM device, reduce the * core-commit to avoid ETM overflow. */ if (adev->periphid & HISI_HIP08_AMBA_MASK == HISI_HIP08_AMBA_ID) etm4_hisi_config_core_commit(1); } #else static void etm4_enable_arch_specific(struct etmv4_drvdata *drvdata) { } #endif /* CONFIG_ETM4X_IMPDEF_FEATURE */ Thanks Qi >> I'll update this patch if this solution is ok : ) >> >> Thanks! >> Qi >>>>>> Do you have any documentation on this back pressure feature? I doubt this is >>>>>> specific to Hip09 platform and as such would prefer to have a more generic >>>>>> approach that works on any platform that supports it. >>>>>> >>>>>> Anyone on the CS mailing list that knows what this is about? >>>>> I believe this is hisilicon specific. May be same across their CPUs, may >>>>> be a specific one. There is no architectural guarantee. >>>>> >>>> This could be an implementation of the feature provided by the >>>> TRCSTALLCTRL register - which allows PE to be stalled in response to >>>> the ETM fifos approaching overflow. >>>> At present we do nothing with this feature as we have yet to see a >>>> target with it implemented, but if this is the case then it is an >>>> ETMv4 architectural feature that could be added into the main driver >>>> code, with use/access gated by the relevent TRCIDR bit. >>>> >>>> Regards >>>> >>>> Mike >>>> >>>> >>>>> Cheers >>>>> Suzuki >>>> >>>> >>>> -- >>>> Mike Leach >>>> Principal Engineer, ARM Ltd. >>>> Manchester Design Centre. UK >>> . >>> >> > > . >