Re: [PATCH v4 2/4] drivers: misc: Add Support for TMR Manager

[Rao, Appana Durga Kedareswara]

Hi Greg,

Thanks for the review.

On 09/09/22 2:10 pm, Greg KH wrote:
> On Fri, Sep 09, 2022 at 11:49:14AM +0530, Appana Durga Kedareswara rao wrote:
> > Triple Modular Redundancy(TMR) subsystem contains three microblaze cores,
> > subsystem is fault-tolerant and continues to operate nominally after
> > encountering an error. Together with the capability to detect and recover
> > from errors, the implementation ensures the reliability of the entire
> > subsystem.  TMR Manager is responsible for performing recovery of the
> > subsystem detects the fault via a break signal it invokes microblaze
> > software break handler which calls the tmr manager driver api to
> > update the error count and status, added support for fault detection
> > feature via sysfs interface.
> >
> > Usage:
> > To know the break handler count(Error count):
> > cat /sys/devices/platform/amba_pl/44a10000.tmr_manager/errcnt
> >
> > Signed-off-by: Appana Durga Kedareswara rao <appana.durga.kedareswara.rao@xxxxxxx>
> > ---
> > Changes for v4:
> > --> None.
> > Changes for v3:
> > --> Corrected month in the sysfs-driver-xilinx-tmr-manager file
> > --> Updated the Kconfig to compile the driver as a module
> > --> Removed unneeded status sysfs attribute
> > Changes for v2:
> > --> Fixed Month in the sysfs description.
> > --> Fixed line over 80 char in driver.
> > --> Replaced kstrtol with kstrtoul as suggested by Michal.
> > --> Added error check for xlnx,magic1 value.
> >
> >   .../testing/sysfs-driver-xilinx-tmr-manager   |  16 ++
> >   MAINTAINERS                                   |   7 +
> >   drivers/misc/Kconfig                          |  10 +
> >   drivers/misc/Makefile                         |   3 +-
> >   drivers/misc/xilinx_tmr_manager.c             | 222 ++++++++++++++++++
> >   5 files changed, 257 insertions(+), 1 deletion(-)
> >   create mode 100644 Documentation/ABI/testing/sysfs-driver-xilinx-tmr-manager
> >   create mode 100644 drivers/misc/xilinx_tmr_manager.c
> >
> > diff --git a/Documentation/ABI/testing/sysfs-driver-xilinx-tmr-manager b/Documentation/ABI/testing/sysfs-driver-xilinx-tmr-manager
> > new file mode 100644
> > index 000000000000..2a97be6ae849
> > --- /dev/null
> > +++ b/Documentation/ABI/testing/sysfs-driver-xilinx-tmr-manager
> > @@ -0,0 +1,16 @@
> > +What:		/sys/devices/platform/amba_pl/<dev>/errcnt
> > +Date:		Sep 2022
> > +Contact:	appana.durga.kedareswara.rao@xxxxxxx
> > +Description:	This control file provides the fault detection count.
> > +		This file cannot be written.
> > +		Example:
> > +		# cat /sys/devices/platform/amba_pl/44a10000.tmr_manager/errcnt
> > +		  1
> > +
> > +What:		/sys/devices/platform/amba_pl/<dev>/dis_block_break
> > +Date:		Sep 2022
> > +Contact:	appana.durga.kedareswara.rao@xxxxxxx
> > +Description:	Write any value to it, This control file enables the break signal.
> > +		This file is write only.
> > +		Example:
> > +		# echo <any value> > /sys/devices/platform/amba_pl/44a10000.tmr_manager/dis_block_break
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index f1390b8270b2..5fc5ec13985e 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -13277,6 +13277,13 @@ W:	http://www.monstr.eu/fdt/
> >   T:	git git://git.monstr.eu/linux-2.6-microblaze.git
> >   F:	arch/microblaze/
> >   
> > +MICROBLAZE TMR MANAGER
> > +M:	Appana Durga Kedareswara rao <appana.durga.kedareswara.rao@xxxxxxx>
> > +S:	Supported
> > +F:	Documentation/ABI/testing/sysfs-driver-xilinx-tmr-manager
> > +F:	Documentation/devicetree/bindings/misc/xlnx,tmr-manager.yaml
> > +F:	drivers/misc/xilinx_tmr_manager.c
> > +
> >   MICROCHIP AT91 DMA DRIVERS
> >   M:	Ludovic Desroches <ludovic.desroches@xxxxxxxxxxxxx>
> >   M:	Tudor Ambarus <tudor.ambarus@xxxxxxxxxxxxx>
> > diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
> > index 94e9fb4cdd76..1508cc29b05a 100644
> > --- a/drivers/misc/Kconfig
> > +++ b/drivers/misc/Kconfig
> > @@ -496,6 +496,16 @@ config VCPU_STALL_DETECTOR
> >   
> >   	  If you do not intend to run this kernel as a guest, say N.
> >   
> > +config TMR_MANAGER
> > +	tristate "Select TMR Manager"
> > +	depends on MICROBLAZE && MB_MANAGER
> > +	help
> > +	  This option enables the driver developed for TMR Manager. The Triple
> > +	  Modular Redundancy(TMR) manager provides support for fault detection
> > +	  via sysfs interface.
>
> What is the module name?
>
> And the fault detection api is in debugfs, not sysfs, right?

Fault injection happens via debugfs in the tmr-inject driver (4/4 patch 
- xilinx_tmr_inject.c) patch, Fault detection is tracked using tmr 
manager errcnt sysfs entry (/sys/devices/platform/amba_pl/<dev>/errcnt).
TMR Manager is responsible for performing recovery of the subsystem 
detects the fault via a break signal it invokes microblaze
software break handler which calls the tmr manager driver api to
update the error count.


Regards,
Kedar.
> thanks,
>
> greg k-h