[ Upstream commit 981fbe3da20a6f35f17977453bce7dfc1664d74f ]
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.
Signed-off-by: James Hutchinson jahutchinson99@googlemail.com Reviewed-by: Antti Palosaari crope@iki.fi Signed-off-by: Sean Young sean@mess.org Signed-off-by: Mauro Carvalho Chehab mchehab+samsung@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/media/dvb-frontends/m88ds3103.c | 9 ++++----- 1 file changed, 4 insertions(+), 5 deletions(-)
diff --git a/drivers/media/dvb-frontends/m88ds3103.c b/drivers/media/dvb-frontends/m88ds3103.c index 31f16105184c0..59a4563c0466e 100644 --- a/drivers/media/dvb-frontends/m88ds3103.c +++ b/drivers/media/dvb-frontends/m88ds3103.c @@ -309,6 +309,9 @@ static int m88ds3103_set_frontend(struct dvb_frontend *fe) u16 u16tmp; u32 tuner_frequency_khz, target_mclk; s32 s32tmp; + static const struct reg_sequence reset_buf[] = { + {0x07, 0x80}, {0x07, 0x00} + };
dev_dbg(&client->dev, "delivery_system=%d modulation=%d frequency=%u symbol_rate=%d inversion=%d pilot=%d rolloff=%d\n", @@ -321,11 +324,7 @@ static int m88ds3103_set_frontend(struct dvb_frontend *fe) }
/* reset */ - ret = regmap_write(dev->regmap, 0x07, 0x80); - if (ret) - goto err; - - ret = regmap_write(dev->regmap, 0x07, 0x00); + ret = regmap_multi_reg_write(dev->regmap, reset_buf, 2); if (ret) goto err;