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 10:16:39 +0800

On Thu, Aug 13, 2020 at 04:47:41AM +0800, Mathieu Poirier wrote:
> On Fri, Aug 07, 2020 at 07:11:38PM +0800, 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)
> > +{
> 
> Not sure adding __exit does anything special here since all the code is
> removed by the kernel anyway.  The same comment goes for the other drivers
> in
> this set.
> 
We still need to remove any reference in other part of Kernel to etm device.
For example, we remove ETM module but keep coresight module. ETM-perf and
coresight-core still could access ETM device structure if etm_perf_symlink()
and coresigh_unregister() are not called in etm_remove. We need clean any
reference to ETM device structure up.

Thanks,
Tingwei

> > +	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);
> > +	}
> > +
> > +	coresight_unregister(drvdata->csdev);
> > +
> > +	return 0;
> > +}
> > +
> >  #ifdef CONFIG_PM
> >  static int etm_runtime_suspend(struct device *dev)
> >  {
> > @@ -937,6 +954,8 @@ static const struct amba_id etm_ids[] = {
> >  	{ 0, 0},
> >  };
> >  
> > +MODULE_DEVICE_TABLE(amba, etm_ids);
> > +
> >  static struct amba_driver etm_driver = {
> >  	.drv = {
> >  		.name	= "coresight-etm3x",
> > @@ -945,6 +964,12 @@ static struct amba_driver etm_driver = {
> >  		.suppress_bind_attrs = true,
> >  	},
> >  	.probe		= etm_probe,
> > +	.remove         = etm_remove,
> >  	.id_table	= etm_ids,
> >  };
> > -builtin_amba_driver(etm_driver);
> > +module_amba_driver(etm_driver);
> > +
> > +MODULE_AUTHOR("Pratik Patel <[email-masked]>");
> > +MODULE_AUTHOR("Mathieu Poirier <[email-masked]>");
> > +MODULE_DESCRIPTION("Arm CoreSight Program Flow Trace driver");
> 
> That should be "Arm CoreSight Embedded Trace Macrocell 3.x driver"
> 
> With the above: 
> 
> Reviewed-by: Mathieu Poirier <[email-masked]>
> 
> > +MODULE_LICENSE("GPL v2");
> > -- 
> > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora
> Forum,
> > a Linux Foundation Collaborative Project
> > 

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