> -----Original Message----- > From: Linux-nvdimm [mailto:linux-nvdimm-boun...@lists.01.org] On Behalf > Of lijun....@dell.com > Sent: Wednesday, March 29, 2017 4:41 PM > To: dan.j.willi...@intel.com; lijunpan2...@gmail.com > Subject: RE: [PATCH v2] libndctl: add support for the MSFT family of DSM > functions
> > -----Original Message----- > > From: Dan Williams [mailto:dan.j.willi...@intel.com] > > > From: Lijun Pan <lijun....@dell.com> > > > > > > This patch retrieves the health data from NVDIMM-N via > > > the MSFT _DSM function[1], following JESD245A[2] standards. > > > Now 'ndctl list --dimms --health --idle' could work > > > on MSFT type NVDIMM-N, but limited to health_state, > > > temperature_celsius, and life_used_percentage. > > ... > Output is something like, > > "health":{ > "health_state":"ok", > "temperature_celsius":193.750000, > "life_used_percentage":1 > } > > If the BIOS returns a value say 45.75, how can it be represented in (__u16) > instead of using a 'double' type? I think the ((__u16) temp & 0x0FFC) already > represents a temperature in 1/16 Celsius granularity. No need to multiple it > by > 16 again. > > Below I quote the section 7.8 of JESD245.pdf > Bit 3 has a resolution of 1/2 Celsius, > Bit 2 has a resolution of 1/4 Celsius, > Bit 1 has 1/8 Celsius, but is reserved, so I assume it be zero, > Bit 0 has 1/16 Celsius, but is reserved, so I assume it be zero. > > ((__u16) temp & 0x0FFC) will only get the bit11 - bit 0. This presents the > 1/16 Celsius resolution, kind of left shifted 4 bits. > So we don't need to do > 'return CMD_MSFT_SMART(cmd)->temp * 16;' again. > > ==== = quotation starts ===== > " > Temperature measurement shall have a minimum resolution of 0.25 Celsius. > Registers containing measured temperature value shall be 16-bits and report > temperature as a 10-bit value based on the following definition. > > Table 3: Temperature value bit definition > Bit15 Bit14 Bit13 Bit12 Bit11 Bit10 Bit9 Bit8 > Reserved Reserved Reserved Reserved 128 64 > 32 16 > Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 > 8 4 2 1 0.5 0.25 Reserved Reserved > > Examples: > > A temperature value of 10.5 Celsius is represented as 0000000010101000b. > > A temperature value of 64.75 Celsius is represented as 0000010000001100b. > " > > ==== quotation ends ======== > > > Lijun > > > > ...so users know what to expect. With that change and addressing > > Linda's comment about the temperature multiplier I think we're good to > > go. > > You should plan to support temperatures compliant with JESD21C Page 4.1.6-2 (TSE2004 SPD EEPROM with Temperature Sensor), which include: * a sign bit to support negative temperatures (in bit 12) * 0.125 and 0.0625 degrees C precision (i.e., bits 1 and 0 are defined) Industrial Grade and Automotive Grade components operate down to -40 degrees C, so negative values will be required. The importance of extra precision is a but fuzzy given that sensor accuracy varies from +/- 1 to +/- 3 degrees C (depending on the temperature range). A software API should pass along all the available information, though. --- Robert Elliott, HPE Persistent Memory _______________________________________________ Linux-nvdimm mailing list Linux-nvdimm@lists.01.org https://lists.01.org/mailman/listinfo/linux-nvdimm
