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Tue, 14 Apr 2020 15:47:07 -0000 (UTC) Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 8D80EC432C2; Tue, 14 Apr 2020 15:47:06 +0000 (UTC) Received: from mail.codeaurora.org (localhost.localdomain [127.0.0.1]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: saiprakash.ranjan) by smtp.codeaurora.org (Postfix) with ESMTPSA id EC16DC433BA; Tue, 14 Apr 2020 15:47:05 +0000 (UTC) MIME-Version: 1.0 Date: Tue, 14 Apr 2020 21:17:05 +0530 From: Sai Prakash Ranjan To: Mathieu Poirier Subject: Re: [PATCH] coresight: tmc: Read TMC mode only when TMC hw is enabled In-Reply-To: <20200413171418.GB28804@xps15> References: <20200409113538.5008-1-saiprakash.ranjan@codeaurora.org> <9a792e3e-5a17-156d-4b59-4a3ec8f9993e@arm.com> <1751aeabd22bee18d2eef0f643883265@codeaurora.org> <20200413171418.GB28804@xps15> Message-ID: <75ef334a7e2cc6d87deecadd12c74f59@codeaurora.org> X-Sender: saiprakash.ranjan@codeaurora.org User-Agent: Roundcube Webmail/1.3.9 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200414_084711_096066_C31C0125 X-CRM114-Status: GOOD ( 22.71 ) 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: Suzuki K Poulose , linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, swboyd@chromium.org, linux-arm-msm-owner@vger.kernel.org, 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 Mathieu, On 2020-04-13 22:44, Mathieu Poirier wrote: > 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. > This works as well, thanks. diff --git a/drivers/hwtracing/coresight/coresight-tmc-etf.c b/drivers/hwtracing/coresight/coresight-tmc-etf.c index d0cc3985b72a..7ffe05930984 100644 --- a/drivers/hwtracing/coresight/coresight-tmc-etf.c +++ b/drivers/hwtracing/coresight/coresight-tmc-etf.c @@ -596,6 +596,11 @@ int tmc_read_prepare_etb(struct tmc_drvdata *drvdata) goto out; } + if (drvdata->mode == CS_MODE_DISABLED) { + ret = -EINVAL; + goto out; + } + /* There is no point in reading a TMC in HW FIFO mode */ mode = readl_relaxed(drvdata->base + TMC_MODE); if (mode != TMC_MODE_CIRCULAR_BUFFER) { Thanks, Sai -- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel