From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1751221AbbJBEsE (ORCPT <rfc822;w@1wt.eu>);
	Fri, 2 Oct 2015 00:48:04 -0400
Received: from mga09.intel.com ([134.134.136.24]:11951 "EHLO mga09.intel.com"
	rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
	id S1750709AbbJBEsB (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
	Fri, 2 Oct 2015 00:48:01 -0400
X-ExtLoop1: 1
X-IronPort-AV: E=Sophos;i="5.17,621,1437462000"; 
   d="scan'208";a="817707544"
From: Alexander Shishkin <alexander.shishkin@linux.intel.com>
To: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Greg KH <gregkh@linuxfoundation.org>, a.p.zijlstra@chello.nl,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Ingo Molnar <mingo@redhat.com>, Jon Corbet <corbet@lwn.net>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Chunyan Zhang <zhang.chunyan@linaro.org>,
        Mike Leach <mike.leach@arm.com>, Tor Jeremiassen <tor@ti.com>,
        Al Grant <al.grant@arm.com>,
        =?utf-8?Q?Pawe?= =?utf-8?Q?=C5=82?= Moll <pawel.moll@arm.com>,
        "linux-arm-kernel\@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
        linux-doc@vger.kernel.org,
        "linux-kernel\@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH 06/20] coresight: etm3x: unlocking tracer in default arch init
In-Reply-To: <CANLsYkwO64CRfcZ+z+=+ucbtOVeOcOoCy+d0GO5sEuTf+Qe0WQ@mail.gmail.com>
References: <1442593594-10665-1-git-send-email-mathieu.poirier@linaro.org> <1442593594-10665-7-git-send-email-mathieu.poirier@linaro.org> <87eghgjg4v.fsf@ashishki-desk.ger.corp.intel.com> <CANLsYkwO64CRfcZ+z+=+ucbtOVeOcOoCy+d0GO5sEuTf+Qe0WQ@mail.gmail.com>
User-Agent: Notmuch/0.20.2 (http://notmuchmail.org) Emacs/24.5.1 (x86_64-pc-linux-gnu)
Date: Fri, 02 Oct 2015 07:47:56 +0300
Message-ID: <87vbap3mgz.fsf@ashishki-desk.ger.corp.intel.com>
MIME-Version: 1.0
Content-Type: text/plain
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Mathieu Poirier <mathieu.poirier@linaro.org> writes:

> On 30 September 2015 at 05:33, Alexander Shishkin
> <alexander.shishkin@linux.intel.com> wrote:
>> Mathieu Poirier <mathieu.poirier@linaro.org> writes:
>>
>>> Calling function 'smp_call_function_single()' to unlock the
>>> tracer and calling it right after to perform the default
>>> initialisation doesn't make sense.
>>>
>>> Moving 'etm_os_unlock()' just before making the default
>>> initialisation results in the same outcome while saving
>>> one call to 'smp_call_function_single()'.
>>>
>>> Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
>>> ---
>>>  drivers/hwtracing/coresight/coresight-etm3x.c | 8 +++++---
>>>  1 file changed, 5 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/hwtracing/coresight/coresight-etm3x.c b/drivers/hwtracing/coresight/coresight-etm3x.c
>>> index c6880c1ade55..a4c158df0fef 100644
>>> --- a/drivers/hwtracing/coresight/coresight-etm3x.c
>>> +++ b/drivers/hwtracing/coresight/coresight-etm3x.c
>>> @@ -1867,6 +1867,11 @@ static void etm_init_arch_data(void *info)
>>>        * certain registers might be ignored.
>>>        */
>>>       etm_clr_pwrdwn(drvdata);
>>> +
>>> +     /* Make sure all registers are accessible */
>>> +     etm_os_unlock(drvdata);
>>
>> In case of co-processor register access, this will end up unlocking the
>> local ETM instead of the one on target cpu, by the looks of it.
>
> "etm_init_arch_data()" is also called from "smp_function_calls()" and
> as such, will end up executing the correct CPU.

Yes, but it doesn't unlock the OSLAR register, which also needs to be
done on target cpu.

Regards,
--
Alex