On Mon, Apr 15, 2019 at 2:07 PM Jagan Teki <ja...@amarulasolutions.com> wrote: > > On Sun, Feb 10, 2019 at 9:49 PM Andre Przywara <andre.przyw...@arm.com> 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. > > How come it reduces to 2KB? I can see the diff size of 160 bytes for gcc-6.3.1 > > ₹ aarch64-linux-gnu-size spl/u-boot-spl* > text data bss dec hex filename > 28376 408 504 29288 7268 spl/u-boot-spl > > ₹ aarch64-linux-gnu-size spl/u-boot-spl* > text data bss dec hex filename > 28216 408 504 29128 71c8 spl/u-boot-spl
Because of section alignment issues? I believe Andre is referring to the size of the whole file. Since it gets loaded as a whole, the total size is what matters, not the size of the individual sections. ChenYu _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot