On Fri, Oct 30, 2015 at 10:08 PM, Al Stone <al.stone@xxxxxxxxxx> wrote: > On 10/30/2015 01:01 PM, Mark Rutland wrote: >> On Fri, Oct 30, 2015 at 02:48:06PM -0400, Sinan Kaya wrote: >> The CSRT is listed under "Want", not "Never" or "Don't Care", so Linaro >> have certainly not said that CSRT will not be supported. If anything, >> they have stated that the table should be supported. > > "Want" means interesting, and probably useful, but no clear indication that > anyone actually needs it. At one point, we thought we might use the CSRT > for describing DMA, but it turns out we have not needed to. Then you are going to have either 1 or 0 DMAC for slave devices, right? The CSRT, unfortunately, the only way how to enumerate DMAC to be used by slave devices. You may look into drivers/dma/acpi-dma.c for usage in Linux. Yes, I know about _DSD, but I don't think it will provide soon any other official mechanisms to what we have now. Better to ask Rafael and Mika. > However, let's make sure we're saying the same thing: the CSRT table is > properly defined in the kernel include/acpi/actbl2.h file so one can read > such a table and use it if they so choose. Nothing that we have done at > Linaro in the arm64 part of the kernel relies on any of the content from > the CSRT, nor does it preclude someone relying on that content. So, the > CSRT is defined, and is usable, but is just not being used -- by Linaro -- > at present. This sounds clear. > If that needs to change, let me know; no one has asked us to use the CSRT > for a DMA engine, and we have not been provided any hardware that requires > it. See above. -- With Best Regards, Andy Shevchenko -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
