Boot data storage schemes for electronic devices
Systems and methods are provided for storing and retrieving boot data (e.g., a first stage bootloader) in and from a non-volatile memory (“NVM”), such as a NAND flash memory. To increase storage reliability, the boot data may be stored in a subset of the pages in a boot data storage area, such as in only lower pages. The subset may be selected based on the specific operating specifications and characteristics of the NVM. To prevent a boot ROM from having to maintain a NVM-specific map of which pages are used to store boot data, the map may be maintained in the NVM itself. For example, the map may be in the form of a linked list, where each page storing boot data can include a pointer that points to the next page that stores boot data.
1. A system comprising:
a volatile memory;
a boot ROM for storing program code to begin loading boot data from non-volatile memory to the volatile memory:
a non-volatile memory comprising:
a plurality of pages that store boot data for booting up the system; and
a map indicating nonconsecutive pages of the non-volatile memory in which the boot data is stored, wherein the map enables execution of the same program code regardless of a manufacturer of the non-volatile memory;
control circuitry that:
reads an initial page of boot data based on the boot ROM;
reads, from the non-volatile memory, the map to ascertain the location of the boot data stored in the nonconsecutive pages other than the initial page; and
loads the boot data from the nonconsecutive pages into the volatile memory using the map.
2. The system of claim 1 , wherein the map comprises a linked list, wherein each of the nonconsecutive pages includes metadata comprising at least one pointer pointing to another of the nonconsecutive pages.
3. The system of claim 2 , wherein the at least one pointer comprises a next page pointer that references a subsequent page of the nonconsecutive pages.
4. The system of claim 2 , wherein the at least one pointer comprises a prior page pointer that references a previous page of the nonconsecutive pages.
5. The system of claim 1 , wherein the map comprises a bitmap that describes the contents of the boot data storage area.
6. The system of claim 1 , wherein the boot data comprises a first stage bootloader.
7. The system of claim 1 , wherein the control circuitry verifies the presence of boot data in the nonconsecutive pages.
8. The system of claim 7 , wherein the control circuitry verifies the presence of boot data in each page by identifying a boot data indicator in each page.
9. The system of claim 7 , wherein the control circuitry verifies the presence of boot data in each page by employing an error correcting code on each page.
10. The system of claim 1 , the system further comprising:
a non-volatile memory interface operable to access the non-volatile memory responsive to requests by the control circuitry.
11. The system of claim 1 , wherein the non-volatile memory comprises NAND flash memory.
12. The system of claim 1 , wherein the control circuitry skips over bad blocks using the map.
13. An electronic device comprising:
a volatile memory;
a non-volatile memory comprising a plurality of pages;
a boot ROM for storing program code that configures the electronic device at bootup to:
read a first page of the non-volatile memory, the first page having boot data and a next page pointer that references a second page of the non-volatile memory, wherein the next page pointer is part of a map indicating nonconsecutive pages of the non-volatile memory in which the boot data is stored, wherein the map enables execution of the same program code regardless of a manufacturer of the non-volatile memory; and
control circuitry operative to:
receive the next page pointer from the first page;
read the second page of the non-volatile memory;
verify that the second page contains boot data; and
load the boot data from the first and second pages into the volatile memory.
14. The electronic device of claim 13 , wherein the electronic device signals a boot failure responsive to a failed verification of the second page.
15. The electronic device of claim 13 , wherein the electronic device:
reads an intervening page between the first page and the second page;
determines, from the next page pointer of the first page, that the intervening page is not the second page; and
discards the intervening page.
16. The electronic device of claim 13 , wherein the electronic device:
reads all of the pages in a boot data storage area of the non-volatile memory, including the first and second pages;
subsequent to reading all of the pages in the boot data storage area, examines the next page pointer of the first page; and
responsive to the examining, discards information obtained from any intervening pages between the first and second pages.
17. The electronic device of claim 13 , wherein the first page further includes a prior page pointer, and wherein the electronic device:
confirms that the prior page pointer indicates that boot data storage begins at the first page.
18. The electronic device of claim 13 , wherein the electronic device:
examines a prior page pointer included in the second page of the non-volatile memory;
verifies that the prior page pointer references back to the first page.
19. The electronic device of claim 13 , wherein the second page contains a second next page pointer that references a third page, and wherein the electronic device:
reads the third page of the non-volatile memory; and
verifies that the third page contains boot data.