On Wed 2015-01-21 13:27:00, Jason Gunthorpe wrote: > On Wed, Jan 21, 2015 at 06:33:12PM +0200, Pantelis Antoniou wrote: > > Hi Alan, > > > > > On Jan 21, 2015, at 18:01 , One Thousand Gnomes <gnomes@xxxxxxxxxxxxxxxxxxx> wrote: > > > > > > On Thu, 15 Jan 2015 22:54:46 +0200 > > > Pantelis Antoniou <pantelis.antoniou@xxxxxxxxxxxx> wrote: > > > > > >> Hi Alan, > > >> > > >>> On Jan 15, 2015, at 22:45 , One Thousand Gnomes <gnomes@xxxxxxxxxxxxxxxxxxx> wrote: > > >>> > > >>> On Thu, 15 Jan 2015 11:47:26 -0700 > > >>> Jason Gunthorpe <jgunthorpe@xxxxxxxxxxxxxxxxxxxx> wrote: > > >>>> It is a novel idea, my concern would be that embedding the FPGA in the > > >>>> DT makes it permanent unswappable kernel memory. > > >>>> Not having the kernel hold the FPGA is best for many uses. > > >>> > > >>> If you have a filesysytem before the FPGA is set up then it belongs in > > >>> the file system. As you presumably loaded the kernel from somewhere there > > >>> ought to be a file system (even an initrd). > > >>> > > >> > > >> Request firmware does not imply keeping it around. You can always re-request > > >> when reloading (although there’s a nasty big of caching that needs to be > > >> resolved with the firmware loader). > > > > > > Which comes down to the same thing. Unless you can prove that there is a > > > path to recover the firmware file that does not have any dependancies > > > upon the firmware executing (and those can be subtle and horrid at times) > > > you need to keep it around for suspend/resume at least and potentially > > > any unexpected error/reset. > > > > > > > In that case the only safe place to put it is in the kernel image itself, which > > is something the firmware loader already supports. > > My point is that the current firmware layer is overly cautious and > FPGAs are very big. My current project on small Xilinx device has a > 10MB programming file. The biggest Xilinx device today has a max > bitfile size around 122MB. > > So keeping that much memory pinned in the kernel when I can prove it > is uncessary for my system (either because there is no suspend/resume > possibility, or because I know the CPU can always access the > filesytem) is very undesirable. Well, your current device aalso has 1GB RAM, no? > Other systems might have to take the ram hit. I'd say the general case is "store bitstream in RAM" we can add optimalizations later. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- 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
