SDIO Fast-Path Overview
Other versions of this page are also available for the following:
.gif "A hyphen indicates that the information in this topic is not relevant for this platform, or that the platform does not support the API that is listed.")
.gif "A checkmark indicates that the information in this topic is relevant for this platform, and that any API listed is also supported on this platform.")
8/28/2008
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.