Subject: Re: [PATCH v8 21/24] coresight: cti: allow cti to be built as a module

From: Mathieu Poirier <[email-masked]>
Date: Tue, 18 Aug 2020 11:42:11 -0600

On Mon, Aug 17, 2020 at 08:14:29PM +0100, Mike Leach wrote:
> Hi,
> 
> On Mon, 17 Aug 2020 at 18:13, Mathieu Poirier
> <[email-masked]> wrote:
> >
> > On Fri, Aug 07, 2020 at 07:11:50PM +0800, Tingwei Zhang wrote:
> > > Allow to build coresight-cti 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-cti by the Makefile
> > > - add an cti_remove function, for module unload
> > > - move cti_remove_conn_xrefs to cti_remove
> > > - add a MODULE_DEVICE_TABLE for autoloading on boot
> > >
> > > Signed-off-by: Tingwei Zhang <[email-masked]>
> > > Tested-by: Mike Leach <[email-masked]>
> >
> > Mike,
> >
> > Please add a "Reviewed-by" tag once you have reviewed this patch.
> >
> 
> Sorry - not sure of the protocol - assumed that my tested-by implied
> reviewed by.

One does not imply the other - in fact many people keep to testing patches
only.  

> 
> Anyway...
> 
> Reviewed-by Mike Leach <[email-masked]>
> 
> > > ---
> > >  drivers/hwtracing/coresight/Kconfig           |  5 ++++-
> > >  drivers/hwtracing/coresight/Makefile          |  4 ++--
> > >  .../{coresight-cti.c => coresight-cti-core.c} | 19 ++++++++++++++++++-
> > >  .../hwtracing/coresight/coresight-platform.c  |  1 +
> > >  drivers/hwtracing/coresight/coresight.c       |  1 +
> > >  5 files changed, 26 insertions(+), 4 deletions(-)
> > >  rename drivers/hwtracing/coresight/{coresight-cti.c => coresight-cti-core.c} (98%)
> > >
> > > diff --git a/drivers/hwtracing/coresight/Kconfig b/drivers/hwtracing/coresight/Kconfig
> > > index f31778dd0b5d..b04aae2ceecc 100644
> > > --- a/drivers/hwtracing/coresight/Kconfig
> > > +++ b/drivers/hwtracing/coresight/Kconfig
> > > @@ -136,7 +136,7 @@ config CORESIGHT_CPU_DEBUG
> > >         module will be called coresight-cpu-debug.
> > >
> > >  config CORESIGHT_CTI
> > > -     bool "CoreSight Cross Trigger Interface (CTI) driver"
> > > +     tristate "CoreSight Cross Trigger Interface (CTI) driver"
> > >       depends on ARM || ARM64
> > >       help
> > >         This driver provides support for CoreSight CTI and CTM components.
> > > @@ -147,6 +147,9 @@ config CORESIGHT_CTI
> > >         halt compared to disabling sources and sinks normally in driver
> > >         software.
> > >
> > > +       To compile this driver as a module, choose M here: the
> > > +       module will be called coresight-cti.
> > > +
> > >  config CORESIGHT_CTI_INTEGRATION_REGS
> > >       bool "Access CTI CoreSight Integration Registers"
> > >       depends on CORESIGHT_CTI
> > > diff --git a/drivers/hwtracing/coresight/Makefile b/drivers/hwtracing/coresight/Makefile
> > > index f2a568b969c4..0359d5a1588f 100644
> > > --- a/drivers/hwtracing/coresight/Makefile
> > > +++ b/drivers/hwtracing/coresight/Makefile
> > > @@ -19,6 +19,6 @@ coresight-etm4x-y := coresight-etm4x-core.o coresight-etm4x-sysfs.o
> > >  obj-$(CONFIG_CORESIGHT_STM) += coresight-stm.o
> > >  obj-$(CONFIG_CORESIGHT_CPU_DEBUG) += coresight-cpu-debug.o
> > >  obj-$(CONFIG_CORESIGHT_CATU) += coresight-catu.o
> > > -obj-$(CONFIG_CORESIGHT_CTI) += coresight-cti.o \
> > > -                             coresight-cti-platform.o \
> > > +obj-$(CONFIG_CORESIGHT_CTI) += coresight-cti.o
> > > +coresight-cti-y := coresight-cti-core.o      coresight-cti-platform.o \
> > >                               coresight-cti-sysfs.o
> >
> > Please align "coresight-cti-sysfs.o" with "coresight-cti-core.o".  The same
> > should be done for the etm3x driver.
> >
> > > diff --git a/drivers/hwtracing/coresight/coresight-cti.c b/drivers/hwtracing/coresight/coresight-cti-core.c
> > > similarity index 98%
> > > rename from drivers/hwtracing/coresight/coresight-cti.c
> > > rename to drivers/hwtracing/coresight/coresight-cti-core.c
> > > index 6bb06c5715db..ca31da6cf1c0 100644
> > > --- a/drivers/hwtracing/coresight/coresight-cti.c
> > > +++ b/drivers/hwtracing/coresight/coresight-cti-core.c
> > > @@ -838,7 +838,6 @@ static void cti_device_release(struct device *dev)
> > >       struct cti_drvdata *ect_item, *ect_tmp;
> > >
> > >       mutex_lock(&ect_mutex);
> > > -     cti_remove_conn_xrefs(drvdata);
> > >       cti_pm_release(drvdata);
> > >
> > >       /* remove from the list */
> > > @@ -853,6 +852,18 @@ static void cti_device_release(struct device *dev)
> > >       if (drvdata->csdev_release)
> > >               drvdata->csdev_release(dev);
> > >  }
> > > +static int __exit cti_remove(struct amba_device *adev)
> > > +{
> > > +     struct cti_drvdata *drvdata = dev_get_drvdata(&adev->dev);
> > > +
> > > +     mutex_lock(&ect_mutex);
> > > +     cti_remove_conn_xrefs(drvdata);
> > > +     mutex_unlock(&ect_mutex);
> >
> > The changelog point out this change but now _why_ it is done - please revise.
> >
> 
> By the time the system calls device_release, all the sysfs links have
> gone so trying to remove them results in errors / crash. Not obvious
> when the drivers were built in as this would be called while the
> system was powering down, but very much noticeable when removing the
> CTI moduie from a running system.
> 
> Regards
> 
> Mike
> 
> > > +
> > > +     coresight_unregister(drvdata->csdev);
> > > +
> > > +     return 0;
> > > +}
> > >
> > >  static int cti_probe(struct amba_device *adev, const struct amba_id *id)
> > >  {
> > > @@ -972,6 +983,7 @@ static const struct amba_id cti_ids[] = {
> > >       CS_AMBA_UCI_ID(0x000bb9ed, uci_id_cti), /* Coresight CTI (SoC 600) */
> > >       { 0, 0},
> > >  };
> > > +MODULE_DEVICE_TABLE(amba, cti_ids);
> > >
> > >  static struct amba_driver cti_driver = {
> > >       .drv = {
> > > @@ -980,6 +992,7 @@ static struct amba_driver cti_driver = {
> > >               .suppress_bind_attrs = true,
> > >       },
> > >       .probe          = cti_probe,
> > > +     .remove         = cti_remove,
> > >       .id_table       = cti_ids,
> > >  };
> > >
> > > @@ -1002,3 +1015,7 @@ static void __exit cti_exit(void)
> > >
> > >  module_init(cti_init);
> > >  module_exit(cti_exit);
> > > +
> > > +MODULE_AUTHOR("Mike Leach <[email-masked]>");
> > > +MODULE_DESCRIPTION("Arm CoreSight CTI Driver");
> > > +MODULE_LICENSE("GPL v2");
> > > diff --git a/drivers/hwtracing/coresight/coresight-platform.c b/drivers/hwtracing/coresight/coresight-platform.c
> > > index bfd44231d7ad..635d55c1d580 100644
> > > --- a/drivers/hwtracing/coresight/coresight-platform.c
> > > +++ b/drivers/hwtracing/coresight/coresight-platform.c
> > > @@ -75,6 +75,7 @@ coresight_find_csdev_by_fwnode(struct fwnode_handle *r_fwnode)
> > >       }
> > >       return csdev;
> > >  }
> > > +EXPORT_SYMBOL_GPL(coresight_find_csdev_by_fwnode);
> > >
> > >  #ifdef CONFIG_OF
> > >  static inline bool of_coresight_legacy_ep_is_input(struct device_node *ep)
> > > diff --git a/drivers/hwtracing/coresight/coresight.c b/drivers/hwtracing/coresight/coresight.c
> > > index 8dcd73ea33b4..f9566d667261 100644
> > > --- a/drivers/hwtracing/coresight/coresight.c
> > > +++ b/drivers/hwtracing/coresight/coresight.c
> > > @@ -289,6 +289,7 @@ void coresight_set_assoc_ectdev_mutex(struct coresight_device *csdev,
> > >       csdev->ect_dev = ect_csdev;
> > >       mutex_unlock(&coresight_mutex);
> > >  }
> > > +EXPORT_SYMBOL_GPL(coresight_set_assoc_ectdev_mutex);
> > >
> > >  static int coresight_enable_sink(struct coresight_device *csdev,
> > >                                u32 mode, void *data)
> > > --
> > > The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum,
> > > a Linux Foundation Collaborative Project
> > >
> 
> 
> 
> -- 
> Mike Leach
> Principal Engineer, ARM Ltd.
> Manchester Design Centre. UK

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