Hello! > From: Sergei Shtylyov, Sent: Monday, June 29, 2020 5:40 PM > > Hello! > > On 29.06.2020 8:24, 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... > > > > I'm sorry again and again. But, do you have any time to look this patch? > > Yes, in the sense of reviewing -- I don't consider it complete. And no, in > the sense of looking into the issue myself... Can we do a per-queue tear-down > and re-init (not necessarily all in 1 patch)? Thank you for your comment! I'm not sure this "re-init" mean. But, we can do a per-queue tear-down if DMAC is still working. And, we can prepare new descriptors for the queue after tear-down. < Tear-down > 1. Set DT_EOS to the desc_bat[queue]. 2. Set DLR.LBAx to 1. 3. Check if DLA.LBAx is cleared. < Prepare new descriptors and start again > 4. Prepare new descriptors. 5. Set DT_LINKFIX to the desc_bat[queue]. 6. Set DLR.LBAx to 1. 7. Check if DLA.LBAx is cleared. I'm thinking doing tear-down and "re-init" of the descriptors is better than just try to wake the subqueue. But, what do you think? Best regards, Yoshihiro Shimoda > > Best regards, > > Yoshihiro Shimoda > > MBR, Sergei
