imx6: Update CONFIG_SPL_STACK defaults in Kconfig

[platform/kernel/u-boot.git] / doc / imx / common / imx6.txt

diff --git a/doc/imx/common/imx6.txt b/doc/imx/common/imx6.txt
index 9007cfb..c5554d8 100644 (file)
--- a/doc/imx/common/imx6.txt
+++ b/doc/imx/common/imx6.txt
@@ -162,3 +162,34 @@ icorem6qdl> nand write ${loadaddr} uboot ${filesize}
 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).