Uncorrectable error correction code (UECC) recovery time improvement
An apparatus comprising non-volatile memory is configured to access a selected unit of encoded SLC data in the non-volatile memory during a first programming phase of a process of folding data stored at a single bit per memory cell to data stored at multiple bits per memory cell. The apparatus recovers the selected unit of SLC data based on redundancy data formed from units of SLC data that data include the selected unit of SLC data. The apparatus saves the recovered selected unit of SLC data to memory. The apparatus uses the saved recovered unit of SLC data during a second programming phase of folding the data stored at a single bit per memory cell to the data stored at multiple bits per memory cell, thereby saving considerable time in not having to again recover the SLC data using the redundancy data.
1. An apparatus comprising:
volatile memory;
a memory interface configured to be connected to non-volatile memory; and
a processor circuit connected to the memory interface and coupled to the volatile memory, the processor circuit configured to:
read a selected unit of encoded single level cell (SLC) data from a first group of non-volatile memory cells in the non-volatile memory into the volatile memory during a first programming phase of a process of folding data stored at a single bit per memory cell in the non-volatile memory to data stored at multiple bits per memory cell in the non-volatile memory;
recover the selected unit of SLC data based on a plurality of other units of SLC data and redundancy data formed from the selected unit of SLC data and the plurality of other units of SLC data in response to a failure to decode the selected unit of encoded SLC data;
save the recovered selected unit of SLC data to memory; and
use the saved recovered unit of SLC data during a second programming phase of folding the data stored at a single bit per memory cell in the non-volatile memory to the data stored at multiple bits per memory cell in the non-volatile memory.
2. The apparatus of claim 1 , wherein:
the processor circuit comprises an error correction engine configured to determine whether the selected unit of encoded SLC data can be recovered by applying an error correcting algorithm to the encoded SLC data; and
the processor circuit is configured to save the recovered selected unit of SLC data to volatile memory coupled to the error correction engine.
3. The apparatus of claim 1 , wherein:
the processor circuit is configured to save the recovered selected unit of SLC data to a second group of non-volatile memory cells in the non-volatile memory.
4. The apparatus of claim 1 , wherein:
the processor circuit is configured to save the recovered selected unit of SLC data to a region of the non-volatile memory that is used as a safe zone.
5. The apparatus of claim 1 , wherein:
the processor circuit is configured to save the recovered selected unit of SLC data to an open block of non-volatile memory cells in the non-volatile memory.
6. The apparatus of claim 1 , wherein:
the first programming phase of the folding comprises a coarse programming phase; and
the second programming phase of the folding comprises a fine programming phase.
7. The apparatus of claim 1 , wherein the processor circuit is further configured to:
store the data at multiple bits per memory cell in a first word line in a block of non-volatile memory cells in the non-volatile memory during the first programming phase of the process of folding the data; and
perform the second programming phase of the process of folding the data after programming data to a second word line in the block of non-volatile memory cells in the non-volatile memory.
8. A method of operating non-volatile storage, the method comprising:
reading, from a first group of non-volatile memory cells, a codeword for a selected single level cell (SLC) page of data during a coarse programming phase of folding SLC data stored at a single bit per non-volatile memory cell to multi-level cell (MLC) data stored at multiple bits per non-volatile memory cell;
applying an error correcting algorithm to the codeword for the selected SLC page during the coarse programming phase;
determining that the selected SLC page is not recovered by applying the error correcting algorithm to the codeword for the selected SLC page during the coarse programming phase;
recovering the selected SLC page using a redundancy page and a plurality of SLC pages other than the selected SLC page, the redundancy page comprising bitwise combinations of the selected SLC page and the plurality of SLC pages other than the selected SLC page;
saving the recovered selected SLC page to a second group of non-volatile memory cells;
reading, from the first group of non-volatile memory cells, the codeword for the selected SLC page during a fine programming phase of folding the SLC data to the MLC data;
applying the error correcting algorithm to the codeword for the selected SLC page during the fine programming phase; and
using the saved recovered selected SLC page during the fine programming phase of folding the SLC data to the MLC data in response to a failure to decode the codeword for the selected SLC page during the fine programming phase.
9. The method of claim 8 , further comprising:
forming the redundancy page from bitwise combinations of the selected SLC page and the plurality of SLC pages other than the selected SLC page; and
storing the redundancy page in the non-volatile storage.
10. The method of claim 8 , wherein saving the recovered selected SLC page to memory comprises:
saving the recovered selected SLC page to non-volatile memory cells that store one bit per memory cell.
11. The method of claim 8 , wherein saving the recovered selected SLC page to memory comprises:
saving the recovered selected SLC page to a block of non-volatile memory cells that are reserved for storing information for managing operation of the non-volatile storage.
12. The method of claim 8 , wherein saving the recovered selected SLC page to memory comprises:
saving the recovered selected SLC page to an open block of non-volatile memory cells.
13. The method of claim 8 , further comprising:
storing the MLC data at multiple bits per memory cell in a first word line of a block of the non-volatile memory cells in the non-volatile storage during the coarse programming phase of folding the SLC data to the MLC data; and
performing the fine programming phase of folding the SLC data to the MLC data after programming data to a second word line in the block of non-volatile memory cells.
14. A non-volatile storage device comprising:
non-volatile memory cells; and
a control circuit configured to:
read a codeword for a selected single level cell (SLC) page in a first block of the non-volatile memory cells during a coarse programming phase of a process of folding SLC data stored at a single bit per memory cell to multi-level cell (MLC) data stored at multiple bits per memory cell in a first word line of a second block of the non-volatile memory cells;
recover the selected SLC page using a page of XOR data formed from a plurality of SLC pages stored in the non-volatile memory cells, the plurality of SLC pages include the selected SLC page;
store the recovered selected SLC page to data latches;
use the recovered selected SLC page in the data latches to perform the coarse programming phase of folding the SLC data to the first word line in the second block;
save the recovered selected SLC page to a third block of the non-volatile memory cells;
perform a coarse programming phase of programing MLC data to a second word line in the second block after performing the coarse programming phase of folding the SLC data to the first word line in the second block, including overwrite the recovered selected SLC page in the data latches;
access the recovered selected SLC page from the third block of the non-volatile memory during a fine programming phase of the process of folding the SLC data to the MLC data, wherein the fine programming phase is performed after the coarse programming phase of the second word line in the second block; and
use the recovered selected SLC page during the fine programming phase to fold the SLC data to the MLC data.
15. The non-volatile storage device of claim 14 , wherein:
the control circuit comprises a memory controller configured to determine whether the codeword for the selected SLC page can be decoded by applying an error correcting algorithm to the codeword for the selected SLC page, the memory controller is configured to recover the selected SLC page using the page of XOR data in response to determining that the codeword for the selected SLC page cannot be decoded by applying the error correcting algorithm.
16. The non-volatile storage device of claim 14 , wherein:
the control circuit is configured to save the recovered selected SLC page to a group of the non-volatile memory cells that store data at a single bit per memory cell.
17. The non-volatile storage device of claim 14 , wherein:
the control circuit is configured to save the recovered selected SLC page to a group of the non-volatile memory cells that are used as a safe zone.
18. The non-volatile storage device of claim 14 , wherein:
the control circuit is configured to save the recovered selected SLC page to a group of the non-volatile memory cells that comprise an open block of non-volatile memory cells.