- Don't use a common buffer in the softc to store per-command data. Reserve
a buffer in the command itself.
- Don't allocate DMA memory for the kernel command structures when all you
really need is DMA memory for the scratch buffer embedded in them. Instead
allocate a slab for the scratch buffers and divide it up as needed.
- Call bus_dmamap_unload() at the completion of commands.
- Preserve and clear the CAM CCB status flags at completion.
- Reorder some low-level command operations to try to close races.
- Limit the simq to 32 commands for now. There are some serious problems
with the driver under load that are not well understood, so keeping the
simq lower helps avoid this. It has been tested at a higher value, but
this is a safe value that doesn't show much performance degredation.
These changes allow the driver to work reliably with >4GB of memory on i386
and amd64, and also work around deadlocks seen under very high load in
certain situations. The work-around is far from ideal, but without and
documentation it is hard to know what the right fix is.
MFC candidate
Add two new arguments to bus_dma_tag_create(): lockfunc and lockfuncarg.
Lockfunc allows a driver to provide a function for managing its locking
semantics while using busdma. At the moment, this is used for the
asynchronous busdma_swi and callback mechanism. Two lockfunc implementations
are provided: busdma_lock_mutex() performs standard mutex operations on the
mutex that is specified from lockfuncarg. dftl_lock() is a panic
implementation and is defaulted to when NULL, NULL are passed to
bus_dma_tag_create(). The only time that NULL, NULL should ever be used is
when the driver ensures that bus_dmamap_load() will not be deferred.
Drivers that do not provide their own locking can pass
busdma_lock_mutex,&Giant args in order to preserve the former behaviour.
sparc64 and powerpc do not provide real busdma_swi functions, so this is
largely a noop on those platforms. The busdma_swi on is64 is not properly
locked yet, so warnings will be emitted on this platform when busdma
callback deferrals happen.
If anyone gets panics or warnings from dflt_lock() being called, please
let me know right away.
Reviewed by: tmm, gibbs
driver at long last!
Many thanks to vaidas.damosevicius@if.lt for keeping this issue alive
and pursuing Intel for a fix, Intel/ICP for working on the driver, and
Sergey Osokin for bringing the original patches up to 5-CURRENT.
prior ICP Vortex models. This driver was developed by Achim Leubner
of Intel (previously with ICP Vortex) and Boji Kannanthanam of Intel.
Submitted by: "Kannanthanam, Boji T" <boji.t.kannanthanam@intel.com>
MFC after: 2 weeks
