Hi Stephen,
On 28 July 2015 at 10:05, Stephen Warren swarren@wwwdotorg.org wrote:
On 07/28/2015 09:50 AM, Simon Glass wrote:
Hi Stephen,
On 28 July 2015 at 09:44, Stephen Warren swarren@wwwdotorg.org wrote:
On 07/28/2015 09:33 AM, Simon Glass wrote:
Hi,
On 27 July 2015 at 11:45, Stephen Warren swarren@wwwdotorg.org wrote:
From: Thierry Reding treding@nvidia.com
For 64-bit ARM SoCs we rely on non-U-Boot code to bring up the CPU in AArch64 mode so that we don't need the SPL. Non-cached memory is not implemented (yet) for 64-bit ARM.
Signed-off-by: Thierry Reding treding@nvidia.com Signed-off-by: Tom Warren twarren@nvidia.com Signed-off-by: Stephen Warren swarren@nvidia.com
include/configs/tegra-common.h | 4 ++++ 1 file changed, 4 insertions(+)
What does start up the CPU? Is this something that will be implemented in SPL later?
At least initially, the plan is to use a separate bootloader on the boot CPU (was named AVP, but got renamed to BPMP lite in Tegra210). It's vaguely possible that U-Boot SPL support will exist in the future, but I'm not sure.
Ah OK. Where does that live? I think SPL would be better.
We haven't yet worked out the logistics of how to release it. I expect it will be a little while yet.
As an aside, I don't think SPL is the right mechanism at least for new Tegra chips, although using the U-Boot code base on the boot CPU might be reasonable, and is something we might look at after we've got the first round SW stack up. The boot CPU and main CPU complex have always been different CPUs and even ARM architectures. While we were able to hack around this with Tegra124 and earlier since they were both 32-bit ARM, so the same compiler and variable sizes etc. could be used, this likely isn't possible on Tegra210 and later, since the boot CPU is 32-bit ARM and the main CPU complex is 64-bit ARM. It'd be better to build two completely separate builds of U-Boot for the two CPU types, and then combine them together during the flash image generation process.
Sounds reasonable. In a way this is similar to SPL works, except I think you are saying that there would be no need for SPL to load U-Boot since they would be packaged together, as now.
My understanding is that the motivation for having SPL at all with Tegra was these CPU differences. So from that POV I suppose Tegra 210 isn't any different.
Regards, Simon