e83bb3e6f3
The tiadc_irq_h(int irq, void *private) function is handling FIFO
overruns by clearing flags, disabling and enabling the ADC to
recover.
If the ADC is running in continuous mode a FIFO overrun happens
regularly. If the disabling of the ADC happens concurrently with
a new conversion. It might happen that the enabling of the ADC
is ignored by the hardware. This stops the ADC permanently. No
more interrupts are triggered.
According to the AM335x Reference Manual (SPRUH73H October 2011 -
Revised April 2013 - Chapter 12.4 and 12.5) it is necessary to
check the ADC FSM bits in REG_ADCFSM before enabling the ADC
again. Because the disabling of the ADC is done right after the
current conversion has been finished.
To trigger this bug it is necessary to run the ADC in continuous
mode. The ADC values of all channels need to be read in an endless
loop. The bug appears within the first 6 hours (~5.4 million
handled FIFO overruns). The user space application will hang on
reading new values from the character device.
Fixes: ca9a563805f7a ("iio: ti_am335x_adc: Add continuous sampling
support")
Signed-off-by: Michael Engl <michael.engl@wjw-solutions.com>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.