Re: [PATCH v4 2/2] i2c_imc: New driver for Intel's iMC, found on LGA2011 chips

[Guenter Roeck <linux-0h96xk9xTtrk1uMJSBkQmQ@public.gmane.org>]

On Thu, Jul 18, 2013 at 02:37:40PM -0700, Andy Lutomirski wrote:
> On Thu, Jul 18, 2013 at 2:33 PM, Guenter Roeck <linux-0h96xk9xTtrk1uMJSBkQmQ@public.gmane.org> wrote:
> > On Thu, Jul 18, 2013 at 11:36:54AM -0700, Andy Lutomirski wrote:
> >> Sandy Bridge Xeon and Extreme chips have integrated memory controllers
> >> with (rather limited) onboard SMBUS masters.  This driver gives access
> >> to the bus.
> >>
> >> Signed-off-by: Andy Lutomirski <luto-kltTT9wpgjJwATOyAt5JVQ@public.gmane.org>
> >> ---
> >>  drivers/i2c/busses/Kconfig   |  15 ++
> >>  drivers/i2c/busses/Makefile  |   1 +
> >>  drivers/i2c/busses/i2c-imc.c | 548 +++++++++++++++++++++++++++++++++++++++++++
> >>  3 files changed, 564 insertions(+)
> >>  create mode 100644 drivers/i2c/busses/i2c-imc.c
> >>
> >> diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
> >> index e837f0e..7636782 100644
> >> --- a/drivers/i2c/busses/Kconfig
> >> +++ b/drivers/i2c/busses/Kconfig
> >> @@ -137,6 +137,21 @@ config I2C_DIMM_BUS
> >>         tristate
> >>         default n
> >>
> >> +config I2C_IMC
> >> +     tristate "Intel iMC (LGA 2011) SMBus Controller"
> >> +     depends on PCI && X86
> >> +     select I2C_DIMM_BUS
> >> +     help
> >> +       If you say yes to this option, support will be included for the Intel
> >> +       Integrated Memory Controller SMBus host controller interface.  This
> >> +       controller is found on LGA 2011 Xeons and Core i7 Extremes.
> >> +
> >> +       It is possibly, although unlikely, that the use of this driver will
> >> +       interfere with your platform's RAM thermal management.
> >> +
> >> +       This driver can also be built as a module.  If so, the module will be
> >> +       called i2c-imc.
> >> +
> >>  config I2C_PIIX4
> >>       tristate "Intel PIIX4 and compatible (ATI/AMD/Serverworks/Broadcom/SMSC)"
> >>       depends on PCI
> >> diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
> >> index 226bb2e..790b63d 100644
> >> --- a/drivers/i2c/busses/Makefile
> >> +++ b/drivers/i2c/busses/Makefile
> >> @@ -15,6 +15,7 @@ obj-$(CONFIG_I2C_AMD8111)   += i2c-amd8111.o
> >>  obj-$(CONFIG_I2C_I801)               += i2c-i801.o
> >>  obj-$(CONFIG_I2C_ISCH)               += i2c-isch.o
> >>  obj-$(CONFIG_I2C_ISMT)               += i2c-ismt.o
> >> +obj-$(CONFIG_I2C_IMC)                += i2c-imc.o
> >>  obj-$(CONFIG_I2C_NFORCE2)    += i2c-nforce2.o
> >>  obj-$(CONFIG_I2C_NFORCE2_S4985)      += i2c-nforce2-s4985.o
> >>  obj-$(CONFIG_I2C_PIIX4)              += i2c-piix4.o
> >> diff --git a/drivers/i2c/busses/i2c-imc.c b/drivers/i2c/busses/i2c-imc.c
> >> new file mode 100644
> >> index 0000000..9643aeb
> >> --- /dev/null
> >> +++ b/drivers/i2c/busses/i2c-imc.c
> >
> > [ ... ]
> >
> >> +
> >> +     i2c_scan_dimm_bus(&ch->adapter);
> >> +
> > Wonder if this should (can) be part of the infrastructure, eg by introducing
> > I2C_CLASS_DIMM.
> 
> If so, it'll have to work differently than the current class bits.
> All they do is determine which drivers get detected, and that
> detection happens by completely generic means that's not really
> applicable to DIMMs (and doesn't work on this bus).
> 
In i2c_detect_address:

	if (adap->class & I2C_CLASS_DIMM)
		return i2c_detect_dimm();


or in i2c_default_probe, call a dimm specific probe function and then
depend on the device detect functions (if that is possible).

Sure, the i2c core code would have to change a bit to accomodate the new
I2C_CLASS_DIMM, but I personally would prefer that to calling
the detect function from the adapter driver.

Personal preference, though; this ultimately depends on the i2c maintainers.

Thanks,
Guenter