linux-kernel - Re: [PATCH v2 00/14] coresight: Implement device claim protocol

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Message-ID: <CANLsYkxvF44MiX8RZtx3yU5yj=nyjbUXOYkv8oV2uYD6CbHENg@mail.gmail.com>
Date:   Wed, 12 Sep 2018 13:42:37 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     "Suzuki K. Poulose" <suzuki.poulose@....com>
Cc:     linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        coresight@...ts.linaro.org, Robert Walker <robert.walker@....com>,
        Al Grant <al.grant@....com>
Subject: Re: [PATCH v2 00/14] coresight: Implement device claim protocol

On Thu, 6 Sep 2018 at 03:08, Suzuki K Poulose <suzuki.poulose@....com> wrote:
>
> Coresight architecture defines CLAIM tags for a device to negotiate
> control of the components (external agent vs self-hosted). Each device
> has a pair of registers (CLAIMSET & CLAIMCLR) for managing the CLAIM
> tags. However, the protocol for the CLAIM tags is IMPLEMENTATION DEFINED.
> PSCI has recommendations for the use of the CLAIM tags to negotiate
> controls for external agent vs self-hosted use, as defined in
> ARM DEN 0022D, Section "6.8.1 Debug and Trace save and restore".
>
> This series implements the recommended protocol by PSCI.
>
> There were two options for the implementation.
>  1) Have the claim/disclaim operations performed from the coresight
>     generic driver - This doesn't work unfortunately for ETM devices
>     as the need cross-CPU calls to access the CLAIM registers. Also,
>     makes it complex for error recovery and reference counting.
>
>  2) Have the claim/disclaim operations performed from the device
>     specific drivers. The disadvantage is that the calls are sprinkled
>     in each driver, but this makes the operation much simpler.
>
> This series implements the method (2). The first part of the series
> prepares different drivers to handle errors from the lower layer
> and clean up the state. The second part of the series updates the
> existing drivers to claim/disclaim the devices as necessary.
>
> Tested with a hacked coresight driver which modifies the external
> claim tag via sysfs handle.
>
> Applies on coresight/next in Mathieu's tree.
>
> Changes since V1:
>  - Handle errors is enabling path and disable only the components
>    that were enabled in the iteration.
>  - Fix build break on arm32 (etm3x)
>  - Update commit description for "coresight: Add support for CLAIM tag protocol"
>
> Suzuki K Poulose (14):
>   coresight: Handle failures in enabling a trace path
>   coresight: tmc-etr: Refactor for handling errors
>   coresight: tmc-etr: Handle errors enabling CATU
>   coresight: tmc-etb/etf: Prepare to handle errors enabling
>   coresight: etm4x: Add support for handling errors
>   coresight: etm3: Add support for handling errors
>   coresight: etb10: Handle errors enabling the device
>   coresight: dynamic-replicator: Handle multiple connections
>   coresight: Add support for CLAIM tag protocol
>   coresight: etmx: Claim devices before use
>   coresight: funnel: Claim devices before use
>   coresight: catu: Claim device before use
>   coresight: dynamic-replicator: Claim device for use
>   coreisght: tmc: Claim device before use
>
>  drivers/hwtracing/coresight/coresight-catu.c       |   6 ++
>  .../coresight/coresight-dynamic-replicator.c       |  79 ++++++++++----
>  drivers/hwtracing/coresight/coresight-etb10.c      |  18 +++-
>  drivers/hwtracing/coresight/coresight-etm3x.c      |  56 +++++++---
>  drivers/hwtracing/coresight/coresight-etm4x.c      |  51 ++++++---
>  drivers/hwtracing/coresight/coresight-funnel.c     |  26 ++++-
>  drivers/hwtracing/coresight/coresight-priv.h       |   7 ++
>  drivers/hwtracing/coresight/coresight-tmc-etf.c    |  95 +++++++++++------
>  drivers/hwtracing/coresight/coresight-tmc-etr.c    |  80 +++++++++-----
>  drivers/hwtracing/coresight/coresight.c            | 118 +++++++++++++++++++--
>  include/linux/coresight.h                          |  20 ++++
>  11 files changed, 434 insertions(+), 122 deletions(-)

I have applied this set.

Thanks,
Mathieu

>
> --
> 2.7.4
>