Hi Hao, On Thu, Apr 04, 2019 at 12:31:47AM +0800, Wu Hao wrote: > On Tue, Apr 02, 2019 at 07:59:25AM -0700, Moritz Fischer wrote: > > Hi Wu, > > > > On Mon, Mar 25, 2019 at 11:07:41AM +0800, Wu Hao wrote: > > > This patch adds support to thermal management private feature for DFL > > > FPGA Management Engine (FME). As thermal throttling is handled by > > > hardware automatically per pre-defined thresholds, this private > > > feature driver only provides read-only sysfs interfaces for user > > > to read temperature, thresholds, threshold policy and other info. > > > > > > Signed-off-by: Luwei Kang <luwei.k...@intel.com> > > > Signed-off-by: Russ Weight <russell.h.wei...@intel.com> > > > Signed-off-by: Xu Yilun <yilun...@intel.com> > > > Signed-off-by: Wu Hao <hao...@intel.com> > > > --- > > > Documentation/ABI/testing/sysfs-platform-dfl-fme | 56 +++++++ > > > drivers/fpga/dfl-fme-main.c | 202 > > > +++++++++++++++++++++++ > > > 2 files changed, 258 insertions(+) > > > > > > diff --git a/Documentation/ABI/testing/sysfs-platform-dfl-fme > > > b/Documentation/ABI/testing/sysfs-platform-dfl-fme > > > index b8327e9..d3aeb88 100644 > > > --- a/Documentation/ABI/testing/sysfs-platform-dfl-fme > > > +++ b/Documentation/ABI/testing/sysfs-platform-dfl-fme > > > @@ -44,3 +44,59 @@ Description: Read-only. It returns socket_id to > > > indicate which socket > > > this FPGA belongs to, only valid for integrated solution. > > > User only needs this information, in case standard numa node > > > can't provide correct information. > > > + > > > +What: > > > /sys/bus/platform/devices/dfl-fme.0/thermal_mgmt/temperature > > > +Date: March 2019 > > > +KernelVersion: 5.2 > > > +Contact: Wu Hao <hao...@intel.com> > > > +Description: Read-only. It returns temperature (in Celsius) of this > > > FPGA > > > + device. > > > + > > > +What: > > > /sys/bus/platform/devices/dfl-fme.0/thermal_mgmt/threshold1 > > > +Date: March 2019 > > > +KernelVersion: 5.2 > > > +Contact: Wu Hao <hao...@intel.com> > > > +Description: Read-only. Read this file to get the temperature > > > threshold1 > > > + (in Celsius). > > > + > > > +What: > > > /sys/bus/platform/devices/dfl-fme.0/thermal_mgmt/threshold2 > > > +Date: March 2019 > > > +KernelVersion: 5.2 > > > +Contact: Wu Hao <hao...@intel.com> > > > +Description: Read-only. Read this file to get the temperature > > > threshold2 > > > + (in Celsius). > > > + > > > +What: > > > /sys/bus/platform/devices/dfl-fme.0/thermal_mgmt/trip_threshold > > > +Date: March 2019 > > > +KernelVersion: 5.2 > > > +Contact: Wu Hao <hao...@intel.com> > > > +Description: Read-only. It returns trip threshold (in Celsius), once > > > FPGA > > > + temperature reaches trip threshold, it triggers a fatal event > > > + to board management controller (BMC) to shutdown FPGA. > > > + > > > +What: > > > /sys/bus/platform/devices/dfl-fme.0/thermal_mgmt/threshold1_status > > > +Date: March 2019 > > > +KernelVersion: 5.2 > > > +Contact: Wu Hao <hao...@intel.com> > > > +Description: Read-only. It returns 1 if temperature reaches > > > threshold1, > > > + otherwise 0. Once temperature reaches threshold1, hardware > > > + will automatically enter throttling state (AP1 - 50% > > > + or AP2 - 90% throttling, see 'threshold1_policy'). > > > + > > > +What: > > > /sys/bus/platform/devices/dfl-fme.0/thermal_mgmt/threshold2_status > > > +Date: March 2019 > > > +KernelVersion: 5.2 > > > +Contact: Wu Hao <hao...@intel.com> > > > +Description: Read-only. It returns 1 if temperature reaches > > > threshold2, > > > + otherwise 0. Once temperature reaches threshold2, hardware > > > + will automatically enter the deepest throttling state (AP6 > > > + - 100% throttling). > > > + > > > +What: > > > /sys/bus/platform/devices/dfl-fme.0/thermal_mgmt/threshold1_policy > > > +Date: March 2019 > > > +KernelVersion: 5.2 > > > +Contact: Wu Hao <hao...@intel.com> > > > +Description: Read-only. Read this file to get the policy of > > > temperature > > > + threshold1. It only supports two value (policy): > > > + 0 - AP2 state (90% throttling) > > > + 1 - AP1 state (50% throttling) > > > > These look like they could directly map to the linux thermal framework, > > any reason you can't use the thermal framework? > > > > The trip stuff literally maps 1:1 to what a thermal driver does, I think > > that's something you'd wanna consider. > > > > Hi Moritz, > > Thanks a lot for the suggestion, actually I feel that the trip points in > thermal > zone are used to indicate cooling actions required for thermal software either > in kernel or userspace. But in this case, such FPGA hardware handles cooling > automatically (yes, driver only expose Read-only sysfs for information), so > software doesn't need to take care of this at all. For this purpose, it seems > that we don't have to put these thresholds as trip points. And per my > understanding, if people use such FPGA device, then they may need to know > what's the current hardware throttling behavior, e.g. 50% vs 90%. These > information can't be provided by standard thermal zone sysfs, so anyway user > needs these sysfs interfaces to know it. But it seems that we still could > create a thermal zone without trip points, it could help if user wants to > connect some external cooling devices via userspace thermal daemon, they can > define whatever trip points they like to activate the external cooling > device. I will consider this further more and come up with a new patch in > v2 patchset.
Generally speaking extending an existing framework with the functionality you want is preferable over rolling 100% your own. So please look into this. Thanks, Moritz
