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@ -3412,76 +3412,6 @@ following configurations: |
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Builds up envcrc with the target environment so that external utils |
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may easily extract it and embed it in final U-Boot images. |
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- CONFIG_ENV_IS_IN_FLASH: |
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Define this if the environment is in flash memory. |
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a) The environment occupies one whole flash sector, which is |
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"embedded" in the text segment with the U-Boot code. This |
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happens usually with "bottom boot sector" or "top boot |
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sector" type flash chips, which have several smaller |
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sectors at the start or the end. For instance, such a |
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layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In |
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such a case you would place the environment in one of the |
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4 kB sectors - with U-Boot code before and after it. With |
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"top boot sector" type flash chips, you would put the |
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environment in one of the last sectors, leaving a gap |
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between U-Boot and the environment. |
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- CONFIG_ENV_OFFSET: |
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Offset of environment data (variable area) to the |
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beginning of flash memory; for instance, with bottom boot |
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type flash chips the second sector can be used: the offset |
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for this sector is given here. |
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CONFIG_ENV_OFFSET is used relative to CONFIG_SYS_FLASH_BASE. |
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- CONFIG_ENV_ADDR: |
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This is just another way to specify the start address of |
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the flash sector containing the environment (instead of |
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CONFIG_ENV_OFFSET). |
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- CONFIG_ENV_SECT_SIZE: |
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Size of the sector containing the environment. |
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b) Sometimes flash chips have few, equal sized, BIG sectors. |
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In such a case you don't want to spend a whole sector for |
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the environment. |
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- CONFIG_ENV_SIZE: |
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If you use this in combination with CONFIG_ENV_IS_IN_FLASH |
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and CONFIG_ENV_SECT_SIZE, you can specify to use only a part |
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of this flash sector for the environment. This saves |
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memory for the RAM copy of the environment. |
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It may also save flash memory if you decide to use this |
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when your environment is "embedded" within U-Boot code, |
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since then the remainder of the flash sector could be used |
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for U-Boot code. It should be pointed out that this is |
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STRONGLY DISCOURAGED from a robustness point of view: |
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updating the environment in flash makes it always |
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necessary to erase the WHOLE sector. If something goes |
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wrong before the contents has been restored from a copy in |
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RAM, your target system will be dead. |
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- CONFIG_ENV_ADDR_REDUND |
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CONFIG_ENV_SIZE_REDUND |
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These settings describe a second storage area used to hold |
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a redundant copy of the environment data, so that there is |
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a valid backup copy in case there is a power failure during |
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a "saveenv" operation. |
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BE CAREFUL! Any changes to the flash layout, and some changes to the |
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source code will make it necessary to adapt <board>/u-boot.lds* |
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accordingly! |
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- CONFIG_ENV_IS_IN_NVRAM: |
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Define this if you have some non-volatile memory device |
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Simon Glass
7 years ago
committed by
Tom Rini