On 10/30/2015 01:01 PM, Mark Rutland wrote: > On Fri, Oct 30, 2015 at 02:48:06PM -0400, Sinan Kaya wrote: >>>>>> It was decided by >>>>>> Linaro that CSRT will not be supported for ARM64. Hrm. I personally decided we didn't have to worry about using the CSRT (specifically, let's wait until someone has a need for it), but I know of no decision to *not* support it. Please cite a source for that claim. >> See this. >> >> https://wiki.linaro.org/LEG/Engineering/Kernel/ACPI/TablePriorities > > 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. 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. 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. > I suspect that the rationale for it not being "Critical" or "Must" is > that it's possible to use contemporary systems without DMA engines, but > we will need support at some point in future. Essentially correct. We (Linaro ACPI team) would be glad to work on it, if needed. We just need to know that someone wants it, and we need to have some way to test it (i.e., aka "hardware"). > I also note that there are Linaro patches adding supoprt for DBG2 [1] , > which is listed as "Never". So the page may be out of date... Sadly, it is indeed out of date, but it is on my TODO list. The DBG2 table was originally listed as "Never" only because of the licensing; this has since changed and is now usable for consoles, so it got worked on and implemented. > Leif, Al? > > [1] https://lkml.org/lkml/2015/9/8/287 > > Thanks, > Mark. > -- ciao, al ----------------------------------- Al Stone Software Engineer Linaro Enterprise Group al.stone@xxxxxxxxxx ----------------------------------- -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
