On 1/13/19 11:13 PM, James Hutchinson wrote:
Ref: https://bugzilla.kernel.org/show_bug.cgi?id=199323
Users are experiencing problems with the DVBSky S960/S960C USB devices
since the following commit:
9d659ae: ("locking/mutex: Add lock handoff to avoid starvation")
The device malfunctions after running for an indeterminable period of
time, and the problem can only be cleared by rebooting the machine.
It is possible to encourage the problem to surface by blocking the
signal to the LNB.
Further debugging revealed the cause of the problem.
In the following capture:
- thread #1325 is running m88ds3103_set_frontend
- thread #42 is running ts2020_stat_work
a> [1325] usb 1-1: dvb_usb_v2_generic_io: >>> 08 68 02 07 80
[1325] usb 1-1: dvb_usb_v2_generic_io: <<< 08
[42] usb 1-1: dvb_usb_v2_generic_io: >>> 09 01 01 68 3f
[42] usb 1-1: dvb_usb_v2_generic_io: <<< 08 ff
[42] usb 1-1: dvb_usb_v2_generic_io: >>> 08 68 02 03 11
[42] usb 1-1: dvb_usb_v2_generic_io: <<< 07
[42] usb 1-1: dvb_usb_v2_generic_io: >>> 09 01 01 60 3d
[42] usb 1-1: dvb_usb_v2_generic_io: <<< 07 ff
b> [1325] usb 1-1: dvb_usb_v2_generic_io: >>> 08 68 02 07 00
[1325] usb 1-1: dvb_usb_v2_generic_io: <<< 07
[42] usb 1-1: dvb_usb_v2_generic_io: >>> 08 68 02 03 11
[42] usb 1-1: dvb_usb_v2_generic_io: <<< 07
[42] usb 1-1: dvb_usb_v2_generic_io: >>> 09 01 01 60 21
[42] usb 1-1: dvb_usb_v2_generic_io: <<< 07 ff
[42] usb 1-1: dvb_usb_v2_generic_io: >>> 08 68 02 03 11
[42] usb 1-1: dvb_usb_v2_generic_io: <<< 07
[42] usb 1-1: dvb_usb_v2_generic_io: >>> 09 01 01 60 66
[42] usb 1-1: dvb_usb_v2_generic_io: <<< 07 ff
[1325] usb 1-1: dvb_usb_v2_generic_io: >>> 08 68 02 03 11
[1325] usb 1-1: dvb_usb_v2_generic_io: <<< 07
[1325] usb 1-1: dvb_usb_v2_generic_io: >>> 08 60 02 10 0b
[1325] usb 1-1: dvb_usb_v2_generic_io: <<< 07
Two i2c messages are sent to perform a reset in m88ds3103_set_frontend:
a. 0x07, 0x80
b. 0x07, 0x00
However, as shown in the capture, the regmap mutex is being handed over
to another thread (ts2020_stat_work) in between these two messages.
From here, the device responds to every i2c message with an 07 message,
and will only return to normal operation following a power cycle.
Use regmap_multi_reg_write to group the two reset messages, ensuring
both are processed before the regmap mutex is unlocked.
I tried to reproduce that issue with pctv 461e, which has em28xx
usb-interface, but without success. Even when I added some sleep between
reset commands and increased tuner statistic polling interval such that
it polls all the time, it works correctly. Device has tuner is connected
to demod i2c bus, which I think is same for your device (it calls demod
i2c mux select for every tuner i2c access).
Taking into account tests I made it is probably issue with usb-interface
i2c adapter instead - for some reason it stops working and starts
returning 07 error all the time. Did any other I2C command succeed after
failure? I mean is there any other i2c client on that bus you could test
if it fails too on error situation?
All in all, fix should be done to usb-interface i2c adapter if possible
unless it has proven issue is somewhere else. You could try to add some
sleep or repeat to i2c adapter in order to see if it helps.
regards
Antti
--
http://palosaari.fi/
