From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S967096AbdAKN7n (ORCPT ); Wed, 11 Jan 2017 08:59:43 -0500 Received: from foss.arm.com ([217.140.101.70]:49256 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752550AbdAKN7m (ORCPT ); Wed, 11 Jan 2017 08:59:42 -0500 Subject: Re: [PATCH] coresight: STM: Balance enable/disable To: Chunyan Zhang , Mathieu Poirier References: <1484047315-14407-1-git-send-email-suzuki.poulose@arm.com> <20170110173637.GA12100@linaro.org> Cc: Pratik Patel , "linux-kernel@vger.kernel.org" , "linux-arm-kernel@lists.infradead.org" , gregkh@linuxfoundation.org, stable@vger.kernel.org From: Suzuki K Poulose Message-ID: Date: Wed, 11 Jan 2017 13:59:38 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/01/17 11:41, Chunyan Zhang wrote: > On 11 January 2017 at 01:36, Mathieu Poirier wrote: >> On Tue, Jan 10, 2017 at 11:21:55AM +0000, Suzuki K Poulose wrote: >>> The stm is automatically enabled when an application sets the policy >>> via ->link() call back by using coresight_enable(), which keeps the >>> refcount of the current users of the STM. However, the unlink() callback >>> issues stm_disable() directly, which leaves the STM turned off, without >>> the coresight layer knowing about it. This prevents any further uses >>> of the STM hardware as the coresight layer still thinks the STM is >>> turned on and doesn't issue an stm_enable(). Even manually enabling >>> the STM via sysfs can't really enable the hw. >>> >>> e.g, >>> >>> $ echo 1 > $CS_DEVS/$ETR/enable_sink >>> $ mkdir -p $CONFIG_FS/stp-policy/$source.0/stm_test/ >>> $ echo 32768 65535 > $CONFIG_FS/stp-policy/$source.0/stm_test/channels >>> $ echo 64 > $CS_DEVS/$source/traceid >>> $ ./stm_app >>> Sending 64000 byte blocks of pattern 0 at 0us intervals >>> Success to map channel(32768~32783) to 0xffffa95fa000 >>> Sending on channel 32768 >>> $ dd if=/dev/$ETR of=~/trace.bin.1 >>> 597+1 records in >>> 597+1 records out >>> 305920 bytes (306 kB) copied, 0.399952 s, 765 kB/s >>> $ ./stm_app >>> Sending 64000 byte blocks of pattern 0 at 0us intervals >>> Success to map channel(32768~32783) to 0xffff7e9e2000 >>> Sending on channel 32768 >>> $ dd if=/dev/$ETR of=~/trace.bin.2 >>> 0+0 records in >>> 0+0 records out >>> 0 bytes (0 B) copied, 0.0232083 s, 0.0 kB/s >>> >>> Note that we don't get any data from the ETR for the second session. >>> >>> Also dmesg shows : >>> >>> [ 77.520458] coresight-tmc 20800000.etr: TMC-ETR enabled >>> [ 77.537097] coresight-replicator etr_replicator@20890000: REPLICATOR enabled >>> [ 77.558828] coresight-replicator main_replicator@208a0000: REPLICATOR enabled >>> [ 77.581068] coresight-funnel 208c0000.main_funnel: FUNNEL inport 0 enabled >>> [ 77.602217] coresight-tmc 20840000.etf: TMC-ETF enabled >>> [ 77.618422] coresight-stm 20860000.stm: STM tracing enabled >>> [ 139.554252] coresight-stm 20860000.stm: STM tracing disabled >>> # End of first tracing session >>> [ 146.351135] coresight-tmc 20800000.etr: TMC read start >>> [ 146.514486] coresight-tmc 20800000.etr: TMC read end >>> # Note that the STM is not turned on via stm_generic_link()->coresight_enable() >>> # and hence none of the components are turned on. >>> [ 152.479080] coresight-tmc 20800000.etr: TMC read start >>> [ 152.542632] coresight-tmc 20800000.etr: TMC read end >>> >>> This patch balances the unlink operation by using the coresight_disable(), >>> keeping the coresight layer in sync with the hardware state. >>> >>> Fixes: commit 237483aa5cf43 ("coresight: stm: adding driver for CoreSight STM component") >>> Cc: Pratik Patel >>> Cc: Mathieu Poirier >>> Cc: Chunyan Zhang >>> Cc: Greg Kroah-Hartman >>> Cc: stable@vger.kernel.org # 4.7+ >>> Reported-by: Robert Walker >>> Signed-off-by: Suzuki K Poulose >>> --- >>> drivers/hwtracing/coresight/coresight-stm.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/drivers/hwtracing/coresight/coresight-stm.c b/drivers/hwtracing/coresight/coresight-stm.c >>> index 3524452..57b7330 100644 >>> --- a/drivers/hwtracing/coresight/coresight-stm.c >>> +++ b/drivers/hwtracing/coresight/coresight-stm.c >>> @@ -356,7 +356,7 @@ static void stm_generic_unlink(struct stm_data *stm_data, >>> if (!drvdata || !drvdata->csdev) >>> return; >>> >>> - stm_disable(drvdata->csdev, NULL); >>> + coresight_disable(drvdata->csdev); >> >> This looks valid to me. >> >> Chunyan, any reason to use stm_disable() directly rather than calling it as part >> of the device OPS in coresight_disable()? > > I don't think there's some special reason for this. I simply hadn't > noticed that these two operations didn't use two balanced functions. Please can I have an Ack/Reviewed -by on it, so that we can push it as a fix. Suzuki