* Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> [120420 08:15]: > On Thu, Apr 19, 2012 at 11:07:42AM -0700, Tony Lindgren wrote: > > * Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx> [120419 10:46]: > > > On Wed, Apr 18, 2012 at 06:39:14PM -0700, Tony Lindgren wrote: > > > > Cool, you almost got it. Got it working for n800 and 770 with the following > > > > patch. Only extremely light testing done now so careful with this patch too.. > > > > > > > > Had to hack in support for the src_port and dst_port that's needed for > > > > omap_set_dma_src/dest_params on omap1. > > > > > > What's the relationship between these ports and the DMA request signal? > > > Is there a document which describes this? > > > > It's the source and destination addresses bus port, so it's more related > > to the addresses than request signal. I guess routing of the DMA request > > signal is what it really does. > > > > I'm now wondering if it might be possible to set it automatically based on > > source and destination address. There's probably some latency involved that requires setting the src and dst port earlier, so I doubt that setting it automatically based on the src and dst address would work correctly. > > There's some information in the omap5912 trm on pages 717 and 718: > > > > http://www.ti.com/litv/pdf/spru742 > > > > It says for CSDP source port "This field identifies the port originator of > > the transfer." > > Is there a reason not to use EMIFF as for the memory port for any DMA > activity between a peripheral and system (kernel) memory? I don't think we have any device to device cases, and it's unlikely that we'll get them either. > It looks to me like TIPB is the right port to use for anything except > camera and LCD? > > If that's true, we can solve the memory side of the problem very easily - > we know that prep_slave_sg() will always souce from system memory, so > the port for that will be known. OK > For the peripheral side of the transfer, I think we should case this on > the request signal as the combinations seem to be very limited - and it > looks like this knowledge is specific to the DMA controller rather than > the peripheral. OK sounds good to me. Regards, Tony -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
