On 11/08/2016 04:50 AM, Jonathan Liu wrote:
On 8 November 2016 at 14:14, Stephen Warren <swar...@wwwdotorg.org> wrote:
On 11/07/2016 07:44 AM, Cédric Schieli wrote:
Raspberry firmware used to pass a FDT blob at a fixed address (0x100),
but this is not true anymore. The address now depends on both the
memory size and the blob size [1].
If one wants to passthrough this FDT blob to the kernel, the most
reliable way is to save its address from the r2/x0 register in the
U-Boot entry point and expose it in a environment variable for
further processing.
This patch just does this:
- save the provided address in the global variable fw_dtb_pointer
- expose it in ${fdt_addr} if it points to a a valid FDT blob
diff --git a/board/raspberrypi/rpi/rpi.c b/board/raspberrypi/rpi/rpi.c
+#ifdef CONFIG_ARM64
+void save_boot_params(unsigned long dtb)
+#else
+void save_boot_params(unsigned long r0, unsigned long r1, unsigned long
dtb)
+#endif
+{
+ fw_dtb_pointer = dtb;
+ save_boot_params_ret();
+}
I think you need to write that function in assembly. This "function" is
called very early during U-Boot startup, before any stack pointer is set up.
You can't guarantee that a function written in C won't attempt to use the
stack, although admittedly with the current code, Makefile, and the Ubuntu
compilers, it just happens not to.
Apparently tegra also uses a C function for save_boot_params in
arch/arm/mach-tegra/board.c...
Yes, that should be fixed. Simon, can you please look into that? I'm not
sure whether the function is even needed; perhaps best to simply delete it.
The comment in arch/arm/include/asm/system.h suggests that
save_boot_params() can be written in C:
/**
* save_boot_params_ret() - Return from save_boot_params()
*
* If you provide save_boot_params(), then you should jump back to this
* function when done. Try to preserve all registers.
*
* If your implementation of save_boot_params() is in C then it is acceptable
That should be fixed too; writing the function in C isn't guaranteed to
work.
* to simply call save_boot_params_ret() at the end of your function. Since
* there is no link register set up, you cannot just exit the function. U-Boot
* will return to the (initialised) value of lr, and likely crash/hang.
*
* If your implementation of save_boot_params() is in assembler then you
* should use 'b' or 'bx' to return to save_boot_params_ret.
*/
void save_boot_params_ret(void);
As mentioned in the commit that added it:
commit 5519912164698b634893913b4408fee736d01d06
Author: Simon Glass <s...@chromium.org>
Date: Mon May 4 11:31:03 2015 -0600
arm: Add a prototype for save_boot_params_ret()
It is convenient for some boards to implement save_boot_params() in C rather
than assembler. Provide a way to return in this case.
Signed-off-by: Simon Glass <s...@chromium.org>
Reviewed-by: Joe Hershberger <joe.hershber...@ni.com>
Aside from that issue, this version looks fine.
Regards,
Jonathan
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