cc9429bcb6
As it seems, some host controllers have issues that can cause them to skip cycles now and then when using large packets. I suspect that this is due to DMA not succeeding in time. If the transmit fifo can't contain more than one packet (big packets), the DMA should provide a new packet each cycle (125us). I am under the impression that my current PCI express test system can't guarantee this. In any case, the patch tries to provide a workaround as follows: The DMA program descriptors are modified such that when an error occurs, the DMA engine retries the descriptor the next cycle instead of stalling. This way no data is lost. The side effect of this is that packets are sent with one cycle delay. This however might not be that much of a problem for certain protocols (e.g. AM824). If they use padding packets for e.g. rate matching they can drop one of those to resync the streams. The amount of skips between two userspace wakeups is counted. This number is then propagated to userspace through the upper 16 bits of the 'dropped' parameter. This allows unmodified userspace applications due to the following: 1) libraw simply passes this dropped parameter to the user application 2) the meaning of the dropped parameter is: if it's nonzero, something bad has happened. The actual value of the parameter at this moment does not have a specific meaning. A libraw client can then retrieve the number of skipped cycles and account for them if needed. Signed-off-by: Pieter Palmers <pieterp@joow.be> Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de> |
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| .. | ||
| config_roms.c | ||
| config_roms.h | ||
| csr.c | ||
| csr.h | ||
| csr1212.c | ||
| csr1212.h | ||
| dma.c | ||
| dma.h | ||
| dv1394-private.h | ||
| dv1394.c | ||
| dv1394.h | ||
| eth1394.c | ||
| eth1394.h | ||
| highlevel.c | ||
| highlevel.h | ||
| hosts.c | ||
| hosts.h | ||
| ieee1394-ioctl.h | ||
| ieee1394.h | ||
| ieee1394_core.c | ||
| ieee1394_core.h | ||
| ieee1394_hotplug.h | ||
| ieee1394_transactions.c | ||
| ieee1394_transactions.h | ||
| ieee1394_types.h | ||
| init_ohci1394_dma.c | ||
| iso.c | ||
| iso.h | ||
| Kconfig | ||
| Makefile | ||
| nodemgr.c | ||
| nodemgr.h | ||
| ohci1394.c | ||
| ohci1394.h | ||
| pcilynx.c | ||
| pcilynx.h | ||
| raw1394-private.h | ||
| raw1394.c | ||
| raw1394.h | ||
| sbp2.c | ||
| sbp2.h | ||
| video1394.c | ||
| video1394.h | ||