Hello! > From: Sergei Shtylyov, Sent: Monday, June 15, 2020 5:13 PM > > Hello! > > On 15.06.2020 8:58, Yoshihiro Shimoda wrote: > > >> From: Yoshihiro Shimoda, Sent: Tuesday, May 26, 2020 6:47 PM > >> > >> According to the report of [1], this driver is possible to cause > >> the following error in ravb_tx_timeout_work(). > >> > >> ravb e6800000.ethernet ethernet: failed to switch device to config mode > >> > >> This error means that the hardware could not change the state > >> from "Operation" to "Configuration" while some tx queue is operating. > >> After that, ravb_config() in ravb_dmac_init() will fail, and then > >> any descriptors will be not allocaled anymore so that NULL porinter > >> dereference happens after that on ravb_start_xmit(). > >> > >> Such a case is possible to be caused because this driver supports > >> two queues (NC and BE) and the ravb_stop_dma() is possible to return > >> without any stopping process if TCCR or CSR register indicates > >> the hardware is operating for TX. > >> > >> To fix the issue, just try to wake the subqueue on > >> ravb_tx_timeout_work() if the descriptors are not full instead > >> of stop all transfers (all queues of TX and RX). > >> > >> [1] > >> https://lore.kernel.org/linux-renesas-soc/20200518045452.2390-1-dirk.behme@xxxxxxxxxxxx/ > >> > >> Reported-by: Dirk Behme <dirk.behme@xxxxxxxxxxxx> > >> Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx> > >> --- > >> I'm guessing that this issue is possible to happen if: > >> - ravb_start_xmit() calls netif_stop_subqueue(), and > >> - ravb_poll() will not be called with some reason, and > >> - netif_wake_subqueue() will be not called, and then > >> - dev_watchdog() in net/sched/sch_generic.c calls ndo_tx_timeout(). > >> > >> However, unfortunately, I didn't reproduce the issue yet. > >> To be honest, I'm also guessing other queues (SR) of this hardware > >> which out-of tree driver manages are possible to reproduce this issue, > >> but I didn't try such environment for now... > >> > >> So, I marked RFC on this patch now. > > > > I'm afraid, but do you have any comments about this patch? > > I agree that we should now reset only the stuck queue, not both but I > doubt your solution is good enough. Let me have another look... Thank you for your comment! I hope this solution is good enough... By the way, there is other topic though, I'm thinking we should not call ravb_{close,open}() in ravb_{suspend,resume}() because this is possible to a race condition between ifconfig up/down and system suspend/resume. In other words, I'm thinking this should not free/reallocate dma memory while netif_running is true. But, what do you think? Best regards, Yoshihiro Shimoda > [...] > > MBR, Sergei
