On 04.06.19 18:15:50, James Morse wrote: > On 03/06/2019 14:10, Robert Richter wrote: > > The +1 looks odd to me also for the edac_mc driver, but I need to take > > a closer look here as well as some logs suggest the grain is > > calculated correctly. > > My theory on this is that ghes_edac.c is generating a grain like 0x1000, > fls() does the > right thing. Other edac drivers are generating a grain like 0xfff to describe > the same > size, fls() is now off-by-one, hence the addition. > I don't have a platform where I can trigger any other edac driver to test > this though. > > The way round this would be to put the grain_bits in struct > edac_raw_error_desc so that > ghes_edac.c can calculate it directly.
I think the grain calculation in edac_mc is broken from the beginning: 53f2d0289875 RAS: Add a tracepoint for reporting memory controller events The log we see in the patch desc is: mc_event: 1 Corrected error:memory read on memory stick DIMM_1A (mc:0 location:0:0:0 page:0x586b6e offset:0xa66 grain:32 syndrome:0x0 area:DMA) The grain reported in mc_event there is probably 8 (quad word, granularity in bytes) and calculates as follows: dimm->grain = 8 e->grain = dimm->grain grain_bits = fls_long(e->grain) + 1 = 4 + 1 = 5 __entry->grain_bits = grain_bits TP_printk() = 1 << __entry->grain_bits = 2 << 5 = 32 So the reported grain of 32 should actually be 8. I think the following is correct: grain_bits = fls_long(e->grain ? e->grain - 1 : 0); This also handles the case if e->grain is not a power of 2. Thoughts? -Robert
