From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andy Shevchenko Subject: Re: usb HC busted? Date: Wed, 06 Jun 2018 18:36:35 +0300 Message-ID: <42ec4ab07d96b4302b875ac9c5eb76675bf85690.camel@linux.intel.com> References: <20180518100650.kfw6wijpncpvqx7j@debian> <6790b352-add3-5531-115c-15db6c9c744d@intel.com> <20180518130458.v73syr3fltdzdzzi@debian> <881d576b-c7c1-ef74-c6bc-68b81371e7e0@intel.com> <20180523212956.n4ztasdffg2aeaku@debian> <80eace7a-976d-65a5-a353-54a2b18edd06@linux.intel.com> <20180604152848.db3msouyi4ektvv6@debian> <06226ecb-baad-cc36-e9e3-797dabb0aa5e@linux.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <06226ecb-baad-cc36-e9e3-797dabb0aa5e-VuQAYsv1563Yd54FQh9/CA@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Mathias Nyman , Sudip Mukherjee Cc: Mathias Nyman , linux-usb-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Christoph Hellwig , iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org, lukaszx.szulc-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org List-Id: iommu@lists.linux-foundation.org On Wed, 2018-06-06 at 17:12 +0300, Mathias Nyman wrote: > On 04.06.2018 18:28, Sudip Mukherjee wrote: > > On Thu, May 24, 2018 at 04:35:34PM +0300, Mathias Nyman wrote: > > > > Odd and unlikely, but to me this looks like some issue in allocating > dma memory > from pool using dma_pool_zalloc() > > Adding people with DMA knowledge to cc, maybe someone knows what is > going on. > > Here's the story: > Sudip sees usb issues on a Intel Atom based board with 4.14.2 kernel. > All tracing points to dma_pool_zalloc() returning the same dma address > block on > consecutive calls. > > In the failing case dma_pool_zalloc() is called 3 - 6us apart. > > <...>-26362 [002] .... 1186.756739: xhci_ring_mem_detail: MATTU > xhci_segment_alloc dma @ 0x000000002d92b000 > <...>-26362 [002] .... 1186.756745: xhci_ring_mem_detail: MATTU > xhci_segment_alloc dma @ 0x000000002d92b000 > <...>-26362 [002] .... 1186.756748: xhci_ring_mem_detail: MATTU > xhci_segment_alloc dma @ 0x000000002d92b000 > > dma_pool_zalloc() is called from xhci_segment_alloc() in > drivers/usb/host/xhci-mem.c > see: > https://elixir.bootlin.com/linux/v4.14.2/source/drivers/usb/host/xhci- > mem.c#L52 > > prints above are custom traces added right after dma_pool_zalloc() For better understanding it would be good to have dma_pool_free() calls debugged as well. Is it possible that something in parallel just fast enough to free the allocated resource from pool? -- Andy Shevchenko Intel Finland Oy