On 05/24/2013 10:43:56 AM, Javi Merino wrote:
The Booting documentation assumes that the initial pagetables are
16KiB but since 1b6ba46 (ARM: LPAE: MMU setup for the 3-level page
table format) they are 20KiB for LPAE kernels. Thus, the
recommendation to put atags or the dtb in the first 16KiB is wrong,
there's only 12KiB of space there in LPAE kernels, so update the
documentation accordingly.
---
Documentation/arm/Booting | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)
Acked-by: Rob Landley <rob@xxxxxxxxxxx>
With one comment:
diff --git a/Documentation/arm/Booting b/Documentation/arm/Booting
index 0c1f475..f6f9cd8 100644
--- a/Documentation/arm/Booting
+++ b/Documentation/arm/Booting
@@ -105,7 +105,7 @@ The tagged list should be stored in system RAM.
The tagged list must be placed in a region of memory where neither
the kernel decompressor nor initrd 'bootp' program will overwrite
-it. The recommended placement is in the first 16KiB of RAM.
+it. The recommended placement is in the first 12KiB of RAM.
4b. Setup the device tree
-------------------------
@@ -120,7 +120,7 @@ tagged list.
The boot loader must pass at a minimum the size and location of the
system memory, and the root filesystem location. The dtb must be
placed in a region of memory where the kernel decompressor will not
-overwrite it. The recommended placement is in the first 16KiB of RAM
+overwrite it. The recommended placement is in the first 12KiB of RAM
with the caveat that it may not be located at physical address 0
since
the kernel interprets a value of 0 in r2 to mean neither a tagged
list
nor a dtb were passed.
@@ -137,8 +137,9 @@ then it is legal for the boot loader to call the
zImage in flash
directly.
The zImage may also be placed in system RAM (at any location) and
-called there. Note that the kernel uses 16K of RAM below the image
-to store page tables. The recommended placement is 32KiB into RAM.
+called there. Note that the kernel may use up to 20KiB of RAM below
+the image to store page tables. The recommended placement is 32KiB
+into RAM.
Now that we have three memory entires, possibly some sort of memory
layout would be in order?
0k-12k boot data (tagged list or device tree)
12k-32k page tables
32k-xxx kernel image
Perhaps at the end of section 4's introduction? It's not quite obvious
from the document...
Rob--
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