SDIO Fast-Path Overview (Windows Embedded CE 6.0)
1/6/2010
Fast-Path operations begin similarly to normal SDIO operations. The process begins when the client driver thread calls SDSynchronousBusRequest and the bus driver builds the bus request. After the bus request is built the bus driver places it in the bus request queue and starts the first bus request. The benefits of a Fast-Path operation only occur after the first bus request is started.
A normal SDIO operation results in the generation of an interrupt when I/O is started on the controller. Fast-Path operations improve performance on high speed SDIO and SD cards by polling for I/O completion instead. A Fast-Path operation does not generate any interrupts and the host controller driver waits until I/O completion to return the I/O status. Once the host controller driver returns the I/O status the bus driver frees the current request, starts the next request, and then returns the final status back to the client driver thread.
For more specific information on the necessary changes for an SDIO bus driver to support Fast-Path, see SDIO Bus Driver Fast-Path Support.