Hi, On 03/23/2017 05:24 PM, Stephen Warren wrote: > On 03/22/2017 06:13 PM, Martin Michlmayr wrote: >> Vagrant Cascadian observed that only 3.5 GB RAM are available on the >> Jetson TX1 development kit. >> >> [ 0.000000] Memory: 3501036K/3670016K available (6780K kernel code, >> 1020K rwdata, 2164K rodata, 3264K init, 634K bss, 168980K reserved, 0K >> cma-reserved) >> >> Interestingly, even u-boot only shows 3.5 GB: >> >> DRAM: 3.5 GiB >> >> This is with mainline u-boot 2016.11 and R23.2 (2016.03-00633-g3ef9cdb). > > That's expected. > > A portion of the top-of-ram holds various carve-outs, such as for the > secure OS and perhaps other purposes like media buffers. Mainline U-Boot > currently hard-codes the size of this unusable RAM area to a very > conservative size. Ideally, U-Boot would query the size of the RAM from > the secure monitor, or retrieve it from information passed by an earlier > stage bootloader. However, doing so relies on using interfaces that may > not be strict ABIs, so we didn't want to make upstream U-Boot use them > at least when we first upstreamed T210 support. So is it just a pessimistic carve-out that not only affect the TX1, or does the TX1 really have a secure monitor? > >> However, 2015.07-rc2-g78c8468 (from R23.1.1) shows: >> >> DRAM: 4 GiB >> >> but that u-boot doesn't boot mainline kernels (some DT errors). > > Conversely, the L4T version of U-Boot is expected to work with the > specific SW stack shipped with L4T, and hence does determine the > carveout size at runtime, and hence allows access to a bit more RAM. I interpret this that *some* memory up there is in deed in use, no matter if we use L4T or mainline Linux/U-Boot, right? Thanks Ralf > > L4T U-Boot should boot an upstream kernel without issue. You may need to > delete a few environment variables to stop U-Boot attempting to copy > some data from the NV-bootloader-supplied DTB into the DTB that U-Boot > itself loads from "disk" and passes to the kernel. > -- > To unsubscribe from this list: send the line "unsubscribe linux-tegra" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-tegra" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
