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

From: Tingwei Zhang <[email-masked]>
Date: Fri, 14 Aug 2020 07:44:22 +0800

On Thu, Aug 13, 2020 at 11:00:04AM -0600, Mathieu Poirier wrote:
> On Thu, 13 Aug 2020 at 04:57, Tingwei Zhang <[email-masked]> wrote:
> >
> > 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.
> 
> I'll take care of ETMv3.  Please wait before sending a new revision
> since I am still reviewing the current set.  I will let you know when
> I am done.
> 

Thanks a lot, Mathieu. I'll wait for your comments.

> >
> > Thanks,
> > Tingwei
> > >
> > > Suzuki
> 
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