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[68.147.8.254]) by smtp.gmail.com with ESMTPSA id v24sm8978016pfm.94.2020.04.13.10.14.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 13 Apr 2020 10:14:20 -0700 (PDT) Date: Mon, 13 Apr 2020 11:14:18 -0600 From: Mathieu Poirier To: Sai Prakash Ranjan Cc: Suzuki K Poulose , mike.leach@linaro.org, swboyd@chromium.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org Subject: Re: [PATCH] coresight: tmc: Read TMC mode only when TMC hw is enabled Message-ID: <20200413171418.GB28804@xps15> References: <20200409113538.5008-1-saiprakash.ranjan@codeaurora.org> <9a792e3e-5a17-156d-4b59-4a3ec8f9993e@arm.com> <1751aeabd22bee18d2eef0f643883265@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1751aeabd22bee18d2eef0f643883265@codeaurora.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-arm-msm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-arm-msm@vger.kernel.org On Mon, Apr 13, 2020 at 01:55:30PM +0530, Sai Prakash Ranjan wrote: > Hi Suzuki, > > On 2020-04-13 04:47, Suzuki K Poulose wrote: > > Hi Sai, > > > > On 04/09/2020 12:35 PM, Sai Prakash Ranjan wrote: > > > Reading TMC mode register in tmc_read_prepare_etb without > > > enabling the TMC hardware leads to async exceptions like > > > the one in the call trace below. This can happen if the > > > user tries to read the TMC etf data via device node without > > > setting up source and the sink first which enables the TMC > > > hardware in the path. So make sure that the TMC is enabled > > > before we try to read TMC data. > > > > So, one can trigger the same SError by simply : > > > > $ cat /sys/bus/coresight/device/tmc_etb0/mgmt/mode > > > > I do not see any SError when I run the above command. > > localhost ~ # cat /sys/bus/coresight/devices/tmc_etf0/mgmt/mode > 0x0 > > And this is most likely due to > > commit cd9e3474bb793dc ("coresight: add PM runtime calls to > coresight_simple_func()") Ok, so this is related to power management (you can ignore my question in the previous email). Regarding function tmc_read_prepare_etb(), the best way to deal with this is probably make sure drvdata->mode != CS_MODE_DISABLED before reading TMC_MODE. If there is a buffer to read it will have been copied when the ETB was disabled and there won't be a need to access the HW. Mathieu > > > And also : > > > > > > > > Kernel panic - not syncing: Asynchronous SError Interrupt > > > CPU: 7 PID: 2605 Comm: hexdump Tainted: G S 5.4.30 > > > #122 > > > Call trace: > > > dump_backtrace+0x0/0x188 > > > show_stack+0x20/0x2c > > > dump_stack+0xdc/0x144 > > > panic+0x168/0x36c > > > panic+0x0/0x36c > > > arm64_serror_panic+0x78/0x84 > > > do_serror+0x130/0x138 > > > el1_error+0x84/0xf8 > > > tmc_read_prepare_etb+0x88/0xb8 > > > tmc_open+0x40/0xd8 > > > misc_open+0x120/0x158 > > > chrdev_open+0xb8/0x1a4 > > > do_dentry_open+0x268/0x3a0 > > > vfs_open+0x34/0x40 > > > path_openat+0x39c/0xdf4 > > > do_filp_open+0x90/0x10c > > > do_sys_open+0x150/0x3e8 > > > __arm64_compat_sys_openat+0x28/0x34 > > > el0_svc_common+0xa8/0x160 > > > el0_svc_compat_handler+0x2c/0x38 > > > el0_svc_compat+0x8/0x10 > > > > > > Fixes: 4525412a5046 ("coresight: tmc: making prepare/unprepare > > > functions generic") > > > Reported-by: Stephen Boyd > > > Signed-off-by: Sai Prakash Ranjan > > > --- > > > drivers/hwtracing/coresight/coresight-tmc.c | 5 +++++ > > > drivers/hwtracing/coresight/coresight-tmc.h | 1 + > > > 2 files changed, 6 insertions(+) > > > > > > diff --git a/drivers/hwtracing/coresight/coresight-tmc.c > > > b/drivers/hwtracing/coresight/coresight-tmc.c > > > index 1cf82fa58289..7bae69748ab7 100644 > > > --- a/drivers/hwtracing/coresight/coresight-tmc.c > > > +++ b/drivers/hwtracing/coresight/coresight-tmc.c > > > @@ -62,11 +62,13 @@ void tmc_flush_and_stop(struct tmc_drvdata > > > *drvdata) > > > void tmc_enable_hw(struct tmc_drvdata *drvdata) > > > { > > > + drvdata->enable = true; > > > writel_relaxed(TMC_CTL_CAPT_EN, drvdata->base + TMC_CTL); > > > } > > > void tmc_disable_hw(struct tmc_drvdata *drvdata) > > > { > > > + drvdata->enable = false; > > > writel_relaxed(0x0, drvdata->base + TMC_CTL); > > > } > > > @@ -102,6 +104,9 @@ static int tmc_read_prepare(struct tmc_drvdata > > > *drvdata) > > > { > > > int ret = 0; > > > + if (!drvdata->enable) > > > + return -EINVAL; > > > + > > > > Does this check always guarantee that the TMC is enabled when > > we actually get to reading the MODE ? This needs to be done > > under the spinlock. > > > > Ok I will make this change. > > Thanks, > Sai > > -- > QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member > of Code Aurora Forum, hosted by The Linux Foundation