Hi Tom, On Fri, 6 Dec 2013 12:18:13 -0500, Tom Rini <[email protected]> wrote:
> On Fri, Dec 06, 2013 at 05:59:37PM +0100, Albert ARIBAUD wrote: > > Hi Tom, > > > > On Fri, 6 Dec 2013 10:48:50 -0500, Tom Rini <[email protected]> wrote: > > > > > Hey all, > > > > > > I've been thinking. We've had a thread on i.MX platforms about fdt > > > being overwritten and needing to be moved to another address. And I've > > > also had an internal problem about fdt being overwritten. So, how about > > > as a rule of thumb we start setting fdt_high (in configs) to > > > memory-start + 512MiB, as that's the lowmem limit we should always have > > > available. This will fix the problem of BSS overwriting the DT, which > > > is the problem we won't catch in normal bootm/bootz usage. Thoughts? > > > > Not sure I'm getting the issue clear, and I would like to avoid (me and > > others) having to switch back and forth between threads. Can you sketch > > the failure scenario in a couple of lines? > > Sure. Lets take am335x_evm builds (so Beaglebone Black/White, etc). > If you start enabling all of the tracing options in the kernel (function > tracing, graphs, etc), you get an uncompressed kernel and BSS that will > use up the first ~16MiB of DDR. We default to placing the DT at about > 15MiB into memory. So the kernel runs, clears BSS and eats the DT. > System now hangs, and depending on debug options set you may or may not > see anything at all from the kernel. U-Boot couldn't detect this > failure because we don't know how big the kernel BSS is, only how big > the zImage is (and where it is) and how big the fdt is and where it is. > No overlaps, go ahead and run. Thanks. The only issue I have with the RFC is that the +512 MiB value will only work with targets which have more than 512 MiB DDR, right? But since you're suggesting this should be set in configs, you are only suggesting +512 MiB, and any target could actually specify a lower value as long as it's greater than or eqal to 16 MiB. Correct? Amicalement, -- Albert. _______________________________________________ U-Boot mailing list [email protected] http://lists.denx.de/mailman/listinfo/u-boot
