On Sun, Feb 10, 2019 at 9:49 PM Andre Przywara <[email protected]> wrote: > > Hi, this is a resend of what I posted some weeks ago, just adding the > missing Signed-off-by: in patch 2/3, as pointed out by Philipp. I used > the opportunity to add his Reviewed-by: tags on the first two patches. > (Many thanks for that!) The rest is unchanged. > ------------------- > > Admittedly this is the long way round to solve some nasty SPL code size > problem, but it looked beneficial to others as well, so here we go: > > arch/arm/include/asm/io.h looks like it's been around since the dawn of > time, and was more or less blindly copied from Linux. > We don't use and don't need most of the definitions, and mainline Linux > got rid of them anyway, so patch 1/3 cleans up this header file to > just contain what we need in U-Boot. > > Patch 2/3 introduces readl/writel_relaxed accessors, which are cheaper, > but more importantly save one (barrier) instruction per accessor. This > helps to bring down code size, since especially DRAM controller inits in > SPLs tend to do a lot of MMIO. > > Consequently patch 3/3 introduces them in the Allwinner H6 DRAM driver, > which reduces the SPL size by a whopping 2KB, due to a twist: > The AArch64 exception table needs to be 2KB aligned, but we don't do > anything special about it the linker script. So depending on where the > code before the vectors ends, we have potentially large padding: > At the moment this last address is 0x1824 for the H6, so the vectors can > only start at 0x2000. By reducing the code size before the vectors by just > (at least) 9 instructions, the vectors start at 0x1800 and we save most of > the padding. > > I understand that the proper solution is to fill the gap before the vectors > with code instead of NOPs, but I couldn't find any obvious way doing this > in the linker script. If anyone has any idea here, I am all ears. > > Cheers, > Andre. > > Andre Przywara (3): > arm: clean up asm/io.h > arm: introduce _relaxed MMIO accessors > sunxi: H6: use writel_relaxed for DRAM timing register accesses
These have build issues with arm32, please send another series. _______________________________________________ U-Boot mailing list [email protected] https://lists.denx.de/listinfo/u-boot
