Re: [PATCH v8 09/24] coresight: etm3x: allow etm3x to be built as a module

Suzuki K Poulose
2020-08-13T09:43:55Z

On 08/07/2020 12:11 PM, Tingwei Zhang wrote:
> From: Kim Phillips <kim.phillips@arm.com>
>
> Allow to build coresight-etm3x as a module, for ease of development.
>
> - Kconfig becomes a tristate, to allow =m
> - append -core to source file name to allow module to
> be called coresight-etm3x by the Makefile
> - add an etm_remove function, for module unload
> - add a MODULE_DEVICE_TABLE for autoloading on boot
>
> Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
> Cc: Leo Yan <leo.yan@linaro.org>
> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
> Cc: Randy Dunlap <rdunlap@infradead.org>
> Cc: Suzuki K Poulose <Suzuki.Poulose@arm.com>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Cc: Russell King <linux@armlinux.org.uk>
> Signed-off-by: Kim Phillips <kim.phillips@arm.com>
> Signed-off-by: Tingwei Zhang <tingwei@codeaurora.org>
> Reviewed-by: Mike Leach <mike.leach@linaro.org>
> ---
> drivers/hwtracing/coresight/Kconfig | 5 +++-
> drivers/hwtracing/coresight/Makefile | 3 ++-
> ...resight-etm3x.c => coresight-etm3x-core.c} | 27 ++++++++++++++++++-
> 3 files changed, 32 insertions(+), 3 deletions(-)
> rename drivers/hwtracing/coresight/{coresight-etm3x.c => coresight-etm3x-core.c} (97%)
>
> diff --git a/drivers/hwtracing/coresight/Kconfig b/drivers/hwtracing/coresight/Kconfig
> index 6433f835fc97..8fd9fd139cf3 100644
> --- a/drivers/hwtracing/coresight/Kconfig
> +++ b/drivers/hwtracing/coresight/Kconfig
> @@ -65,7 +65,7 @@ config CORESIGHT_SINK_ETBV10
> special enhancement or added features.
>
> config CORESIGHT_SOURCE_ETM3X
> - bool "CoreSight Embedded Trace Macrocell 3.x driver"
> + tristate "CoreSight Embedded Trace Macrocell 3.x driver"
> depends on !ARM64
> select CORESIGHT_LINKS_AND_SINKS
> help
> @@ -74,6 +74,9 @@ config CORESIGHT_SOURCE_ETM3X
> This is primarily useful for instruction level tracing. Depending
> the ETM version data tracing may also be available.
>
> + To compile this driver as a module, choose M here: the
> + module will be called coresight-etm3x.
> +
> config CORESIGHT_SOURCE_ETM4X
> bool "CoreSight Embedded Trace Macrocell 4.x driver"
> depends on ARM64
> diff --git a/drivers/hwtracing/coresight/Makefile b/drivers/hwtracing/coresight/Makefile
> index 19497d1d92bf..d619cfd0abd8 100644
> --- a/drivers/hwtracing/coresight/Makefile
> +++ b/drivers/hwtracing/coresight/Makefile
> @@ -11,7 +11,8 @@ obj-$(CONFIG_CORESIGHT_SINK_TPIU) += coresight-tpiu.o
> obj-$(CONFIG_CORESIGHT_SINK_ETBV10) += coresight-etb10.o
> obj-$(CONFIG_CORESIGHT_LINKS_AND_SINKS) += coresight-funnel.o \
> coresight-replicator.o
> -obj-$(CONFIG_CORESIGHT_SOURCE_ETM3X) += coresight-etm3x.o coresight-etm-cp14.o \
> +obj-$(CONFIG_CORESIGHT_SOURCE_ETM3X) += coresight-etm3x.o
> +coresight-etm3x-y := coresight-etm3x-core.o coresight-etm-cp14.o \
> coresight-etm3x-sysfs.o
> obj-$(CONFIG_CORESIGHT_SOURCE_ETM4X) += coresight-etm4x.o \
> coresight-etm4x-sysfs.o
> diff --git a/drivers/hwtracing/coresight/coresight-etm3x.c b/drivers/hwtracing/coresight/coresight-etm3x-core.c
> similarity index 97%
> rename from drivers/hwtracing/coresight/coresight-etm3x.c
> rename to drivers/hwtracing/coresight/coresight-etm3x-core.c
> index bf22dcfd3327..82b333c40006 100644
> --- a/drivers/hwtracing/coresight/coresight-etm3x.c
> +++ b/drivers/hwtracing/coresight/coresight-etm3x-core.c
> @@ -895,6 +895,23 @@ static int etm_probe(struct amba_device *adev, const struct amba_id *id)
> return ret;
> }
>
> +static int __exit etm_remove(struct amba_device *adev)
> +{
> + struct etm_drvdata *drvdata = dev_get_drvdata(&adev->dev);
> +
> + etm_perf_symlink(drvdata->csdev, false);
> +
> + if (--etm_count == 0) {
> + cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING);
> + if (hp_online)
> + cpuhp_remove_state_nocalls(hp_online);
> + }
> +

As mentioned in the previous version, this needs fixing
similar to the etm4x to avoid races with etm_count. I understand
that it is an exisiting problem. But this set exposes it more
due to etm_remove() calls and is much more probable to hit it.

Suzuki