On Wed, Aug 10, 2011 at 02:20:59PM +0530, Viresh Kumar wrote: > Currently we request DMA channels at probe time and free them at remove. They > are always occupied, irrespective of their usage. > > They must be allocated when they are required and must be freed after we are > done with transfers. So that they can be used by other users.
Which DMA engine driver requires this? Normally, when we have DMA engine drivers with multiple request signals, the slave peripheral side publishes several virtual channels which are claimed by the peripheral drivers. This (amongst other things) allows the peripheral drivers to hold claim to one of the virtual channels all the time that it's required. This actually results in better usage of the DMA controller, as the virtual channels can be assigned to physical channels dynamically according to what the physical channels are doing. Plus, actually, the idea that DMA channels should be a short-term thing is broken as soon as you start considering things like UARTs, where you need a channel tied up long-term for the receive side of things. ------------------------------------------------------------------------------ uberSVN's rich system and user administration capabilities and model configuration take the hassle out of deploying and managing Subversion and the tools developers use with it. Learn more about uberSVN and get a free download at: http://p.sf.net/sfu/wandisco-dev2dev _______________________________________________ spi-devel-general mailing list spi-devel-general@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/spi-devel-general
