iio: adc: ti_am335x_adc: Protect FIFO1 from concurrent access
authorVignesh R <vigneshr@ti.com>
Wed, 17 Aug 2016 12:13:00 +0000 (17:43 +0530)
committerJonathan Cameron <jic23@kernel.org>
Sun, 21 Aug 2016 18:47:58 +0000 (19:47 +0100)
commit90c43ec6997a892448f1f86180a515f59cafd8a3
treebd0c0b2d354ee2e7dcdac528c03b137d581a2381
parentca64d4bc80a88845f7e1e266dbff798f928bcc06
iio: adc: ti_am335x_adc: Protect FIFO1 from concurrent access

It is possible that two or more ADC channels can be simultaneously
requested for raw samples, in which case there can be race in access to
FIFO data resulting in loss of samples.
If am335x_tsc_se_set_once() is called again from tiadc_read_raw(), when
ADC is still acquired to sample one of the channels, the second process
might be put into uninterruptible sleep state. Fix these issues, by
protecting FIFO access and channel configurations with a mutex. Since
tiadc_read_raw() might take anywhere between few microseconds to few
milliseconds to finish execution (depending on averaging and delay
values supplied via DT), its better to use mutex instead of spinlock.

Fixes: 7ca6740cd1cd4 ("mfd: input: iio: ti_amm335x: Rework TSC/ADC synchronization")
Signed-off-by: Vignesh R <vigneshr@ti.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
drivers/iio/adc/ti_am335x_adc.c