On Mon, Apr 15, 2019 at 1:21 PM André Przywara <andre.przyw...@arm.com> wrote: > > On 15/04/2019 07:22, Jagan Teki wrote: > > Hi, > > > On Mon, Apr 15, 2019 at 11:40 AM Chen-Yu Tsai <w...@kernel.org> wrote: > >> > >> 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. > > > > Well, the input for final sunxi-spl.bin would be u-boot-spl and the > > above shows the size of file as well 29128 bytes with -160 bytes from > > 29288. > > > > Since the size of sunxi-spl.bin is truncated to 32K, I couldn't see > > any difference either. > > As mentioned in the commit messasge, this is a fragile topic. Since > commit ef331e3685fe ("armv8: Disable exception vectors in SPL by > default") we disable the SPL exception vectors by default now, so the > numbers are now different.
Sorry, I over looked the commit messages. > You should be able to see the 2K saving with the SPL exception vectors > explicitly enabled in menuconfig. Oh. So I enabled the vectors via ARMV8_SPL_EXCEPTION_VECTORS=y but it seems increased the SPL size. ₹ aarch64-linux-gnu-size spl/u-boot-spl text data bss dec hex filename 30130 408 504 31042 7942 spl/u-boot-spl _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de https://lists.denx.de/listinfo/u-boot