e7663ef5ae
Detecting a timeout is ok, but we also need to assert a STOP command on
the bus in order to prevent it from generating interrupts when there are
no on going transfers.
Example: very long transmission.
1. ocores_xfer: START a transfer
2. ocores_isr : handle byte by byte the transfer
3. ocores_xfer: goes in timeout [[bugfix here]]
4. ocores_xfer: return to I2C subsystem and to the I2C driver
5. I2C driver : it may clean up the i2c_msg memory
6. ocores_isr : receives another interrupt (pending bytes to be
transferred) but the i2c_msg memory is invalid now
So, since the transfer was too long, we have to detect the timeout and
STOP the transfer.
Another point is that we have a critical region here. When handling the
timeout condition we may have a running IRQ handler. For this reason I
introduce a spinlock.
In order to make easier to understan locking I have:
- added a new function to handle timeout
- modified the current ocores_process() function in order to be protected
by the new spinlock
Like this it is obvious at first sight that this locking serializes
the execution of ocores_process() and ocores_process_timeout()
Signed-off-by: Federico Vaga <federico.vaga@cern.ch>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
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.