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

From: Tingwei Zhang <[email-masked]>
Date: Thu, 13 Aug 2020 18:56:55 +0800

On Thu, Aug 13, 2020 at 05:47:22PM +0800, Suzuki K Poulose wrote:
> On 08/07/2020 12:11 PM, Tingwei Zhang wrote:
> >From: Kim Phillips <[email-masked]>
> >
> >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 <[email-masked]>
> >Cc: Leo Yan <[email-masked]>
> >Cc: Alexander Shishkin <[email-masked]>
> >Cc: Randy Dunlap <[email-masked]>
> >Cc: Suzuki K Poulose <[email-masked]>
> >Cc: Greg Kroah-Hartman <[email-masked]>
> >Cc: Russell King <[email-masked]>
> >Signed-off-by: Kim Phillips <[email-masked]>
> >Signed-off-by: Tingwei Zhang <[email-masked]>
> >Reviewed-by: Mike Leach <[email-masked]>
> >---
> >  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.
> 
OK. I'll fix this. Can you help to review ETM4 fix? If that's fine,
I'll make similar fix here.

Unfortunately, I don't have any device with ETM3. Can anyone help
to verify the function on ETM3? I'll really appreciate that.

Thanks,
Tingwei
> Suzuki

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