Hi Mike, On Thu, Mar 1, 2012 at 9:29 AM, Mike Frysinger <vap...@gentoo.org> wrote: > On Wednesday 29 February 2012 17:22:26 Graeme Russ wrote: >> On Thu, Mar 1, 2012 at 6:04 AM, Mike Frysinger wrote: >> > On Tuesday 28 February 2012 18:32:57 Graeme Russ wrote: >> >> And this is why I dislike the implementation - You have to do all sorts >> >> of weird calucations to put things in the right place when, in fact, >> >> the location of gd and bd in memory is totally irrelavent. >> > >> > right, that's why i minimized the pain for Blackfin users -- this is all >> > handled in the arch's config-pre.h header. board porters only need to >> > declare the size of regions they care about (monitor and heap sizes). >> > >> >> Ow, ouch! - And that padding makes things more fun - The memory layout >> >> is >> >> >> >> U-Boot | gd | pad | bd | pad | heap >> > >> > fwiw, i documented the Blackfin memory layout: >> > http://docs.blackfin.uclinux.org/doku.php?id=bootloaders:u-boot:memory-la >> > yout >> >> I had a look at this and noticed that you statically allocate locations for >> gd and bd (CONFIG_SYS_GBL_DATA_ADDR, CONFIG_SYS_BD_INFO_ADDR) >> >> Considering that: >> >> a) the gd pointer is in a register (P3) and thus easily locatable by a >> debugger, and; >> b) the bd pointer is in gd >> >> Is there any reason not to have gd and bd in BSS? > > in the Blackfin case, most likely not. we don't do relocation, and the bss is > cleared long before board_init_f() gets called. the only reason for allowing > the config to override would be if someone wanted to put gd/bd into on-chip L1 > data, but i can't imagine this structure being performance critical enough to > warrant that.
I thought as much - I moved gd/bd into BSS for x86 without really thinking about why everyone else calculates the location of these data structures around the stack and heap. The longer I think about it, the more I think that it was not a bad move and that maybe other arches can follow suit as part of standardising the init sequences Regards, Graeme _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
