Bah; I wrote this email about a week ago, but never sent it. Sorry. g.
On 11/26/07, Stephen Neuendorffer <[EMAIL PROTECTED]> wrote: > > I've pushed the current state up to > git://git.xilinx.com/gen-mhs-devtree.git for your perusing. Comments > below. > > > -----Original Message----- > > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On > > Behalf Of Grant Likely > > Sent: Sunday, November 25, 2007 2:47 PM > > To: Stephen Neuendorffer; Segher Boessenkool; David Gibson; > > Jon Loeliger > > Cc: [EMAIL PROTECTED]; > > linuxppc-dev@ozlabs.org; Michal Simek; git > > Subject: Re: Xilinx EDK BSP generation of device trees for > > microblaze and PowerPC > > > > On 11/24/07, Stephen Neuendorffer > > <[EMAIL PROTECTED]> wrote: > > > > > > > Thanks for all this work; comments below. > > > > > > > > Here's what I've gotten so far: > > > > > > Hard_Ethernet_MAC: [EMAIL PROTECTED] { > > > #address-cells = <1>; > > > #size-cells = <1>; > > > [EMAIL PROTECTED] { > > > compatible = > > "xlnx,xps-ll-temac-1.00.a", > > > "xlnx,xps-ll-temac"; > > > > Drop "xlnx,xps-ll-temac"; it's 100% made up. This should be simply: > > compatible = "xlnx,xps-ll-temac-1.00.a" for version 1.00.a and > > compatible = > > "xlnx,xps-ll-temac-<version>","xlnx,xps-ll-temac-1.00.a" for a future > > version if it maintains register level compatibility. > > > > "xlnx,xps-ll-temac" is far to ambiguous. > > What if it was: compatible = "xlnx,xps-ll-temac-1.00.a", > "xlnx,xps-ll-temac-1"? Here's what I've learned: There is no such thing as a perfect device tree. Either hardware bugs will be discovered at a later date which make compatible inaccurate, or a better understanding of the device will come along which will change the understood best practices for describing the device. My opinion is the best strategy against claiming something that's not true, or won't be true in the fucture, is to strive for uniqueness and describe only what you are certain of. Be conservative instead of liberal in the compatible case; ie. it's easier to teach the driver about other versions it can bind against than it is to teach it about exceptions to certain versions of the hardware (when binding). In this particular case the problem still stands that the VHDL engineer may make a non backward compatible change in version xlnx,xps-ll-temac-1.00.c or -1.03.c. You just don't know until it happens. Stick with what is known and don't try to extrapolate to a 'generic' version when there is no guarantee that it will remain generic. When sticking with real version numbers, it is quite safe to claim compatibility with an older version number because you've probably tested it; something which isn't so safe when you attempt to make up generic versions. > > Basically, I don't want to be responsible for declaring what versions of > IP are backward compatible with ll-temac-1.00.a, and I think it's bad > software design to put that list into the dts generator anyway. In > theory, at least, all ip with the same major version should be > compatible. Yes, but at the point of releasing, you've probably tested it so the risk is very low. > > > > interrupt-parent = <&xps_intc_0>; > > > interrupts = < 3 0 >; > > > llink-connected = <&PIM3>; > > > > What's this property for? > > So that the ll_temac knows whether to use dma or fifo code and where the > dma or fifo control/interrupts are. > > > > > > reg = < 81c00000 40 >; > > > > If these registers are addressable, then the parent needs a > > 'ranges' property. > > I thought ranges weren't necessary in a 1:1 mapping? At the very least there needs to be an empty 'ranges' property in order for it to work Cheers, g. -- Grant Likely, B.Sc., P.Eng. Secret Lab Technologies Ltd. [EMAIL PROTECTED] (403) 399-0195 _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@ozlabs.org https://ozlabs.org/mailman/listinfo/linuxppc-dev
