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The use of a memcpy() during a spinlock operation will cause very long
thread context switch delays if the flash chip bandwidth is low and the
data to be copied large, because a spinlock will disable preemption.
For example: A flash with 6,5 MB/s bandwidth will cause under ubifs,
which request sometimes 128 KiB (the flash erase size), a preemption delay of
20 milliseconds. High priority threads will not be served during this
time, regardless whether this threads access the flash or not. This behavior
breaks real time.
The patch changes all the use of spin_lock operations for xxxx->mutex
into mutex operations, which is exact what the name says and means.
I have checked the code of the drivers and there is no use of atomic
pathes like interrupt or timers. The mtdoops facility will also not be used
by this drivers. So it is dave to replace the spin_lock against mutex.
There is no performance regression since the mutex is normally not
acquired.
Changelog:
06.03.2010 First release
26.03.2010 Fix mutex[1] issue and tested it for compile failure
Signed-off-by: Stefani Seibold <stefani@seibold.net>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
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Additionally, some excessive newlines removed.
Signed-off-by: Michael Roth <mroth@nessie.de>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
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Signed-off-by: Alexey Korolev <akorolev@infradead.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
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We have two components to manage LPDDR flash memories in Linux.
1. It is a driver for chip probing and reading its capabilities
2. It is a device operations driver.
Signed-off-by: Alexey Korolev <akorolev@infradead.org>
Acked-by: Jared Hulbert <jaredeh@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
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Driver which handles device command operation.
Details on device operations are available here:
http://www.numonyx.com/Documents/Datasheets/DS-315768_Velocity-Discrete.pdf
Signed-off-by: Alexey Korolev <akorolev@infradead.org>
Acked-by: Jared Hulbert <jaredeh@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
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LPDDR flash chips are based on completely new kind of chips probing.
Device capabilities are available via special request.
We sent field request command which contains Major and Minor numbers - and
recieve corresponend value.
All requests are performed within PFOW window.
Detailed information about qinfo records can be found here:
http://www.numonyx.com/Documents/Datasheets/DS-315768_Velocity-Discrete.pdf
Signed-off-by: Alexey Korolev <akorolev@infradead.org>
Acked-by: Jared Hulbert <jaredeh@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
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