On Mon, Dec 19, 2016 at 10:53:32AM +0000, Andre Przywara wrote: > Hi, > > On 19/12/16 09:57, Maxime Ripard wrote: > > On Mon, Dec 19, 2016 at 01:50:06AM +0000, Andre Przywara wrote: > >> From: Jens Kuske <jensku...@gmail.com> > >> > >> So far the DRAM driver for the H3 SoC (and apparently boot0/libdram as > >> well) only applied coarse delay line settings, with one delay value for > >> all the data lines in each byte lane and one value for the control lines. > >> > >> Instead of setting the delays for whole bytes only allow setting it for > >> each individual bit. Also add support for address/command lane delays. > >> > >> For the purpose of this patch the rules for the existing coarse settings > >> were just applied to the new scheme, so the actual register writes don't > >> change for the H3. Other SoCs will utilize this feature later properly. > >> > >> With a stock GCC 5.3.0 this increases the dram_sun8i_h3.o code size from > >> 2296 to 2344 Bytes. > >> > >> [Andre: move delay parameters into macros to ease later sharing, use > >> defines for numbers of delay registers, extend commit message] > >> > >> Signed-off-by: Jens Kuske <jensku...@gmail.com> > >> Signed-off-by: Andre Przywara <andre.przyw...@arm.com> > > > > I said it earlier, but some comments on these new fields would really > > be welcome to document the structure and what values they're supposed > > to hold. > > I guess you know as much as I do on this topic.
I'd say that you know much more than I do on this one ;) > Apparently there are delays to compensate for differing trace lengths on > the PCB, one for every bit line. On the 32-bit DRAM controller these are > grouped in four groups of 8 bits each (hence byte lane). > > Please keep in mind that there is no easily available documentation, > some parts are just copying what boot0/libdram does. > As we don't know the exact meaning of these fields, I prefer to not add > any guesses here. > I was hoping that the defines I added in this version would shed some > light on this? I am pretty sure of their meaning, but that's as far as > it goes. For instance I have no idea what the units are, for cycles they > are quite big. > > So frankly I don't really know what to add here still. Ok. > I can elaborate on how to get these actual values from an existing > boot0/libdram, but that would be more of a documentation patch than > actual code. That would still be very valuable, if it makes sense, you always can put that as a separate patch. Thanks, Maxime -- Maxime Ripard, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com
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