On Wednesday 25 February 2015 21:45:22 Pali Rohár wrote: > On Wednesday 25 February 2015 19:48:55 Mario Limonciello wrote: > > On 02/20/2015 02:41 PM, Pali Rohár wrote: > > > On Friday 20 February 2015 20:56:23 Mario Limonciello > > > wrote: > > > > > > resetafter=0 means to never reset (even if driver receive > > > e.g thousand invalid packets). I think this is very > > > dangerous if there will be other bugs either in linux > > > driver or some other HW problems. > > > > > > For ALPS issue I added resetafter = pktsize * 2 (Allow 2 > > > invalid packets without resetting device). Cannot you find > > > something similar for synaptics touchpads on XPS? (pktsize > > > for ALPS is 6, no idea how big are synaptics packets). > > > > Pali, > > > > I've done some experimentation with increasing the size to > > resetafter to up to pktsize * 4. It will decrease the > > number of occurrences of this problem, but the problem > > still occurs eventually. pktsize for synaptics is 6 as > > well. Would you recommend to continue to go higher than > > that? Since out_of_sync_cnt is reset when a full packet > > gets received, some arbitrarily high number should likely > > fix it to. > > > > That being said, if you try to more closely follow what > > Windows does for the mouse, it's not issuing a reconnect no > > matter how much bad data is received. > > I believe problem is similar to one as with ALPS devices. > Driver always receive 6 bytes packet of data (no new byte is > inserted and no byte is never lost), just one byte in packet > is incorrect (does not match specification). > > Setting resetafter to > 0 prevent problems when driver enters > into undefined state (either by bug in driver of other SW/HW > problem). So I think setting resetafter to 0 is not good idea. > > But if we know that setting resetafter to 4*pktsize is not > enough (e.g. with experimenting you saw that driver received > more then 4 invalid packets consecutively), set it to higher > value. > > I think it is still good idea to ignore maximally as many > packets which can be received in time which is equal to > resetting device. > > E.g. when period of time in which we are dropping all packets > is higher then time needed to reset touchpad, we should stop > dropping packets and immediately reset touchpad. In this case > we could hit maybe problem in driver (there can be bugs) or > touchpad is in some bad state and out-of-sync... > > So if your tests show that there are never invalid 10 packets > consecutively, then set resetafter to 10 packets. Value 10 is > still not high and if it fix problem with touchpad I think it > is acceptable. But rather ask Dmitry what he thinks about it. > This is just my opinion. Hello Mario, have you patched synaptics driver with some resetafter parameter? And have some team in dell found reason for invalid packets? -- Pali Rohár pali.rohar@xxxxxxxxx
Attachment:
signature.asc
Description: This is a digitally signed message part.
