Hi Magnus, On Tuesday, 19 June 2018 08:43:31 EEST Magnus Damm wrote: > On Tue, Jun 19, 2018 at 11:15 AM, Laurent Pinchart wrote: > > On Sunday, 17 June 2018 03:08:02 EEST Marek Vasut wrote: > >> On 06/16/2018 05:44 PM, Laurent Pinchart wrote: > >>> On Saturday, 16 June 2018 02:42:30 EEST Marek Vasut wrote: > >>>> On 06/16/2018 01:21 AM, Laurent Pinchart wrote: > >>>>> On Friday, 15 June 2018 15:00:31 EEST Marek Vasut wrote: > >>>>>> On 06/15/2018 01:43 PM, Marek Vasut wrote: [snip] > >>>>>>> Yet, I have to wonder if ATF doesn't already contain some sort of > >>>>>>> standard SMC call to get memory topology. It surprises me that it > >>>>>>> wouldn't. > >>>>>> > >>>>>> In fact, Laurent (CCed) was solving some similar issue with lossy > >>>>>> decomp and I think this involved some passing of memory layout > >>>>>> information from ATF to U-Boot too, or am I mistaken ? > >>>>> > >>>>> That's correct, ATF stores information about the memory layout at a > >>>>> fixed address in system memory, and U-Boot can read it. > >>>> > >>>> Well, that sounds good ! Maybe we can avoid adding SMC call altogether > >>>> then? :) > >>> > >>> I'd prefer that, yes. > >>> > >>> Let's not duplicate the mechanism used to pass FCNL information from > >>> ATF to U- Boot, but instead create a data table format that can store > >>> all the information we need, in an easily extensible way. > >>> > >>> To see how the mechanism is implemented for FCNL, search for 47FD7000 > >>> in the Renesas ATF sources > >>> (git://github.com/renesas-rcar/arm-trusted-firmware.git). > >> > >> For everyone involved, can you explain what FCNL is ? ;-) > > > > FCNL is Frame Compression Near Lossless. It's a way to reduce memory > > bandwidth by transparent compression and decompression of video frames. > > Compression is handled by an IP core called FCP, and decompression is > > handled by the DRAM controller. ATF programs the DRAM controller with > > ranges of memory addresses that will be dynamically decompressed. The > > registers containing those ranges are accessible in secure mode only, so > > neither U-Boot nor Linux can read them. That's why ATF has to pass the > > information to U-Boot, in order to add the ranges as reserved memory in > > DT. > > Thanks for the clarification. I wonder how much of the split between > ATF and "the rest" can be adjusted. It smells like just a software > architecture policy, my gut feeling is that LIFEC can be programmed to > adjust the assignment between secure side and "regular". At least it > can do so for a wide range of bus masters. However if this is the case > for FCNL remains to be seen. > > As a side note, for FCNL I personally would prefer a more dynamic > solution where we manage physically contiguous ranges from Linux > during run time instead of relying of statically setup windows. So would I, but whether we can be allowed to access those registers from Linux isn't my decision :-/ > >> Any yes, I agree this sounds good. I had a discussion on the U-Boot IRC > >> about passing the memory configuration around and the result is > >> basically the same -- pass a table from ATF to U-Boot. If there's > >> already something, great. -- Regards, Laurent Pinchart
