imx6: Update CONFIG_SPL_STACK defaults in Kconfig
Update the Kconfig entry to have the correct defaults for i.MX6
platforms, and move the existing large comment from imx6_spl.h to
doc/imx/common/imx6.txt so that it's not lost.
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/doc/imx/common/imx6.txt b/doc/imx/common/imx6.txt
index 9007cfb..c5554d8 100644
--- a/doc/imx/common/imx6.txt
+++ b/doc/imx/common/imx6.txt
@@ -162,3 +162,34 @@
NAND write: device 0 offset 0x200000, size 0x8fd26
589094 bytes written: OK
icorem6qdl>
+
+SPL Stack size and location notes
+---------------------------------
+
+If we have CONFIG_MX6_OCRAM_256KB then see Figure 8.4.1 in IMX6DQ Reference
+manuals:
+ - IMX6DQ OCRAM (IRAM) is from 0x00907000 to 0x0093FFFF
+ - BOOT ROM stack is at 0x0093FFB8
+ - if icache/dcache is enabled (eFuse/strapping controlled) then the
+ IMX BOOT ROM will setup MMU table at 0x00938000, therefore we need to
+ fit between 0x00907000 and 0x00938000.
+ - Additionally the BOOT ROM loads what they consider the firmware image
+ which consists of a 4K header in front of us that contains the IVT, DCD
+ and some padding thus 'our' max size is really 0x00908000 - 0x00938000
+ or 192KB
+ - Pad SPL to 196KB (4KB header + 192KB max size). This allows to write the
+ SPL/U-Boot combination generated with u-boot-with-spl.imx directly to a
+ boot media (given that boot media specific offset is configured properly).
+and if we don't, see Figure 8-3 in IMX6SDL Reference manuals:
+ - IMX6SDL OCRAM (IRAM) is from 0x00907000 to 0x0091FFFF
+ - BOOT ROM stack is at 0x0091FFB8
+ - if icache/dcache is enabled (eFuse/strapping controlled) then the
+ IMX BOOT ROM will setup MMU table at 0x00918000, therefore we need to
+ fit between 0x00907000 and 0x00918000.
+ - Additionally the BOOT ROM loads what they consider the firmware image
+ which consists of a 4K header in front of us that contains the IVT, DCD
+ and some padding thus 'our' max size is really 0x00908000 - 0x00918000
+ or 64KB
+ - Pad SPL to 68KB (4KB header + 64KB max size). This allows to write the
+ SPL/U-Boot combination generated with u-boot-with-spl.imx directly to a
+ boot media (given that boot media specific offset is configured properly).