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From: Suzuki K Poulose <suzuki.poulose@arm.com>
To: Linu Cherian <linuc.decode@gmail.com>
Cc: linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	Mark Rutland <mark.rutland@arm.com>,
	maz@kernel.org, Anshuman Khandual <anshuman.khandual@arm.com>,
	catalin.marinas@arm.com,
	Coresight ML <coresight@lists.linaro.org>,
	linux-kernel@vger.kernel.org, james.morse@arm.com,
	Will Deacon <will@kernel.org>, Mike Leach <mike.leach@linaro.org>
Subject: Re: [PATCH 08/10] coresight: trbe: Workaround TRBE errat overwrite in FILL mode
Date: Tue, 7 Sep 2021 10:18:57 +0100	[thread overview]
Message-ID: <e7241294-d7a3-2286-0bcd-a0cdbec77ffc@arm.com> (raw)
In-Reply-To: <CAAHhmWjR6XYo5j_h3jfLsmWzqD9i9L-pHq=zrrdrw9YTXmuCqg@mail.gmail.com>

Hi Linu

On 06/08/2021 17:09, Linu Cherian wrote:
> Hi Suzuki,
> 
> On Wed, Jul 28, 2021 at 7:23 PM Suzuki K Poulose <suzuki.poulose@arm.com> wrote:
>>
>> ARM Neoverse-N2 (#2139208) and Cortex-A710(##2119858) suffers from
>> an erratum, which when triggered, might cause the TRBE to overwrite
>> the trace data already collected in FILL mode, in the event of a WRAP.
>> i.e, the TRBE doesn't stop writing the data, instead wraps to the base
>> and could write upto 3 cache line size worth trace. Thus, this could
>> corrupt the trace at the "BASE" pointer.
>>
>> The workaround is to program the write pointer 256bytes from the
>> base, such that if the erratum is triggered, it doesn't overwrite
>> the trace data that was captured. This skipped region could be
>> padded with ignore packets at the end of the session, so that
>> the decoder sees a continuous buffer with some padding at the
>> beginning.
> 
> Just trying to understand,
> Is there a possibility that lost data results in partial trace packets
> towards the end of the buffer ? Or its always guaranteed that
> trace packet end is always aligned with buffer end/limit ?
> Thinking of a case when formatting is disabled.

Yes, trace could be partial towards the end with TRBE in the FILL mode.
The TRBE doesn't add any formatting and is thus raw ETE trace which
doesn't have any alignment requirements. This the case even without
the work around.

Suzuki

  reply	other threads:[~2021-09-07  9:19 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-28 13:52 [PATCH 00/10] arm64: Self-hosted trace related erratum workarouds Suzuki K Poulose
2021-07-28 13:52 ` [PATCH 01/10] coresight: trbe: Add infrastructure for Errata handling Suzuki K Poulose
2021-08-02  6:43   ` Anshuman Khandual
2021-09-07  9:04     ` Suzuki K Poulose
2021-09-09  2:55       ` Anshuman Khandual
2021-07-28 13:52 ` [PATCH 02/10] coresight: trbe: Add a helper to calculate the trace generated Suzuki K Poulose
2021-07-30 10:01   ` Anshuman Khandual
2021-07-28 13:52 ` [PATCH 03/10] coresight: trbe: Add a helper to pad a given buffer area Suzuki K Poulose
2021-07-30 10:05   ` Anshuman Khandual
2021-07-28 13:52 ` [PATCH 04/10] coresight: trbe: Decouple buffer base from the hardware base Suzuki K Poulose
2021-07-30 10:53   ` Anshuman Khandual
2021-07-28 13:52 ` [PATCH 05/10] coresight: trbe: Allow driver to choose a different alignment Suzuki K Poulose
2021-07-30 11:02   ` Anshuman Khandual
2021-07-30 14:29     ` Suzuki K Poulose
2021-07-28 13:52 ` [PATCH 06/10] arm64: Add Neoverse-N2, Cortex-A710 CPU part definition Suzuki K Poulose
2021-07-30 11:26   ` Anshuman Khandual
2021-07-30 14:31     ` Suzuki K Poulose
2021-08-02 11:21   ` Catalin Marinas
2021-08-02 11:21   ` Catalin Marinas
2021-07-28 13:52 ` [PATCH 07/10] arm64: Add erratum detection for TRBE overwrite in FILL mode Suzuki K Poulose
2021-08-02  7:44   ` Anshuman Khandual
2021-08-02 11:22   ` Catalin Marinas
2021-08-06 12:44   ` Linu Cherian
2021-09-07  9:10     ` Suzuki K Poulose
2021-07-28 13:52 ` [PATCH 08/10] coresight: trbe: Workaround TRBE errat " Suzuki K Poulose
2021-08-03 10:25   ` Anshuman Khandual
2021-09-07  9:58     ` Suzuki K Poulose
2021-09-09  4:21       ` Anshuman Khandual
2021-09-09  8:37         ` Suzuki K Poulose
2021-08-06 16:09   ` Linu Cherian
2021-09-07  9:18     ` Suzuki K Poulose [this message]
2021-07-28 13:52 ` [PATCH 09/10] arm64: Enable workaround for TRBE " Suzuki K Poulose
2021-08-02  9:34   ` Anshuman Khandual
2021-08-02 11:24   ` Catalin Marinas
2021-07-28 13:52 ` [PATCH 10/10] arm64: errata: Add workaround for TSB flush failures Suzuki K Poulose
2021-07-29  9:55   ` Marc Zyngier
2021-07-29 10:41     ` Suzuki K Poulose
2021-08-02  9:12       ` Anshuman Khandual
2021-08-02  9:35         ` Marc Zyngier
2021-08-03  3:51           ` Anshuman Khandual
2021-09-08 13:39             ` Suzuki K Poulose
2021-08-02 11:27   ` Catalin Marinas

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