Dear Arnd: > -----Original Message----- > From: Arnd Bergmann <arnd@xxxxxxxx> > Sent: Monday, February 7, 2022 3:48 PM > To: Tony Huang <tonyhuang.sunplus@xxxxxxxxx> > Cc: Rob Herring <robh+dt@xxxxxxxxxx>; DTML <devicetree@xxxxxxxxxxxxxxx>; > Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>; Derek Kiernan > <derek.kiernan@xxxxxxxxxx>; Dragan Cvetic <dragan.cvetic@xxxxxxxxxx>; Arnd > Bergmann <arnd@xxxxxxxx>; gregkh <gregkh@xxxxxxxxxxxxxxxxxxx>; Tony > Huang 黃懷厚 <tony.huang@xxxxxxxxxxx>; Wells Lu 呂芳騰 > <wells.lu@xxxxxxxxxxx> > Subject: Re: [PATCH v8 2/2] misc: Add iop driver for Sunplus SP7021 > > On Mon, Feb 7, 2022 at 7:30 AM Tony Huang > <tonyhuang.sunplus@xxxxxxxxx> wrote: > > > > IOP(8051) embedded inside SP7021 which is used as Processor for I/O > > control, monitor RTC interrupt and cooperation with CPU & PMC in power > > management purpose. > > The IOP core is DQ8051, so also named IOP8051, it supports dedicated > > JTAG debug pins which share with SP7021. > > In standby mode operation, the power spec reach 400uA. > > > > Signed-off-by: Tony Huang <tonyhuang.sunplus@xxxxxxxxx> > > --- > > Changes in v8: > > - Addressed comments from Greg KH. > > > > Documentation/ABI/testing/sysfs-platform-soc@B | 28 ++ > > MAINTAINERS | 2 + > > drivers/misc/Kconfig | 20 ++ > > drivers/misc/Makefile | 1 + > > drivers/misc/sunplus_iop.c | 463 > +++++++++++++++++++++++++ > > 5 files changed, 514 insertions(+) > > create mode 100644 Documentation/ABI/testing/sysfs-platform-soc@B > > create mode 100644 drivers/misc/sunplus_iop.c > > > > diff --git a/Documentation/ABI/testing/sysfs-platform-soc@B > > b/Documentation/ABI/testing/sysfs-platform-soc@B > > new file mode 100644 > > index 0000000..d26d6f5 > > --- /dev/null > > +++ b/Documentation/ABI/testing/sysfs-platform-soc@B > > @@ -0,0 +1,28 @@ > > +What: > /sys/devices/platform/soc@B/9c000400.iop/sp_iop_mailbox > > +Date: January 2022 > > +KernelVersion: 5.16 > > +Contact: Tony Huang <tonyhuang.sunplus@xxxxxxxxx> > > +Description: > > + Show IOP's mailbox0 register data. > > + Format: %x > > + > > +What: > /sys/devices/platform/soc@B/9c000400.iop/sp_iop_mode > > +Date: January 2022 > > +KernelVersion: 5.16 > > +Contact: Tony Huang <tonyhuang.sunplus@xxxxxxxxx> > > +Description: > > + Read-Write. > > + > > + Write this file. > > + Operation mode of IOP is switched to standby mode by > writing > > + "1" to sysfs. > > + Operation mode of IOP is switched to normal mode by > writing > > + "0" to sysfs. > > + Writing of other values is invalid. > > + > > + Read this file. > > + Show operation mode of IOP. "0" is normal mode. "1" is > standby > > + mode. > > + Format: %x > > As discussed before, I would suggest leaving out all custom attributes for now, > and first hooking up the driver to all the in-kernel subsystems. > > The mailbox0 register data definitely feels like an implementation detail, not > something that should be exposed to user space as an interface. > > For standby mode, this would normally be handled by the power management > subsystem in the kernel. not a custom interface. From your earlier description, > I assume this interface puts the main CPU into standby mode, not the IOP, > right? > > CPU standby is handled by the cpuidle subsystem, so you need a driver in > drivers/cpuidle/ to replace your sysfs attribute. > If you plan to hook up the driver to multiple subsystems, keeping a generic > driver file is ok, so you'll end up with two driver modules, with one of them > calling into the other, using > EXPORT_SYMBOL() to link between them. > The purpose of adding sysfs is only for users to debug. So this is not needed? Thanks
