From: Kegl Rohit <keglro...@gmail.com> Sent: Friday, November 13, 2020 8:21 PM > On Fri, Nov 13, 2020 at 8:33 AM Kegl Rohit <keglro...@gmail.com> wrote: > > > > > What are the addresses of the ring entries? > > > I bet there is something wrong with the cache coherency and/or > > > flushing. > > > > > > So the MAC hardware has done the write but (somewhere) it isn't > > > visible to the cpu for ages. > > > > CMA memory is disabled in our kernel config. > > So the descriptors allocated with dma_alloc_coherent() won't be CMA memory. > > Could this cause a different caching/flushing behaviour? > > Yes, after tests I think it is caused by the disabled CMA. > > @Andy > I could find this mail and the attached "i.MX6 dma memory bufferable > issue.pptx" in the archive > https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fmarc.info > %2F%3Fl%3Dlinux-netdev%26m%3D140135147823760&data=04%7C01 > %7Cfugang.duan%40nxp.com%7C121e73ec66684a125e2a08d887cea578%7C > 686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637408668924362983 > %7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJ > BTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=e7Cm24Ay1Ay52UKtzT > BiX9KlhuublndP30vnwxAaugM%3D&reserved=0 > Was this issue solved in some kernel versions later on? > Is CMA still necessary with a 5.4 Kernel?
Yes, CMA is required. Otherwise it requires one patch for L2 cache.
