| Tom Rini | 8b83b53 | 2022-05-26 13:46:32 -0400 | [diff] [blame] | 1 | U-Boot for Freescale i.MX7 |
| 2 | |
| 3 | SPL Stack size and location notes |
| 4 | --------------------------------- |
| 5 | See figure 6-22 in i.MX 7Dual/Solo Reference manuals: |
| 6 | - IMX7D/S OCRAM free area RAM (OCRAM) is from 0x00910000 to |
| 7 | 0x00946C00. |
| 8 | - Set the stack at the end of the free area section, at 0x00946BB8. |
| 9 | - The BOOT ROM loads what they consider the firmware image |
| 10 | which consists of a 4K header in front of us that contains the IVT, DCD |
| 11 | and some padding. However, the manual also states that the ROM uses the |
| 12 | OCRAM_EPCD and OCRAM_PXP areas for itself. While the SPL is free to use |
| 13 | this range for stack and malloc, the SPL itself must fit below 0x920000, |
| 14 | or the image will be truncated in at least some boot modes like USB SDP. |
| 15 | Thus our max size is really 0x00920000 - 0x00912000. If necessary, |
| 16 | CONFIG_SPL_TEXT_BASE could be moved to 0x00911000 to gain 4KB of space |
| 17 | for the SPL, but 56KB should be more than enough for the SPL. |
| 18 | - Pad SPL to 68KB (4KB header + 56KB max size + 8KB extra padding) |
| 19 | The extra padding could be removed, but this value was used historically |
| 20 | based on an incorrect CONFIG_SPL_MAX_SIZE definition. |
| 21 | This allows to write the SPL/U-Boot combination generated with |
| 22 | u-boot-with-spl.imx directly to a boot media (given that boot media specific |
| 23 | offset is configured properly). |