View Issue Details
| ID | Project | Category | View Status | Date Submitted | Last Update |
|---|---|---|---|---|---|
| 0004881 | UBoot | U-Boot | public | 2021-10-04 16:45 | 2021-10-05 10:50 |
| Reporter | derksen | Assigned To | |||
| Priority | normal | Severity | minor | Reproducibility | have not tried |
| Status | resolved | Resolution | fixed | ||
| Target Version | fsimx8mm-Y2021.04 | Fixed in Version | fsimx8mm-Y2021.04 | ||
| Summary | 0004881: mxs_nand: Reduce malloc usage in SPL | ||||
| Description | mxs_nand: Reduce malloc usage in SPL The mxs_nand driver allocates a buffer for doing its DMA transfers. This buffer is already used very early for identifying the chip and reading the ONFI data. This means when the buffer is allocated, the final size of a NAND page is not yet known. So the buffer is allocated with a "worst case" in mind, i.e. 16 KB page size and nearly 2 KB OOB size. For the same reason, struct nand_buffers defines buffers of the same size. In the end we have around 36 KB of buffers. So the first idea is to use pointers ecccalc, ecccode and databuf in struct nand_buffers instead of fixed size arrays. Then these arrays can be allocated dynamically with the appropriate sizes when the page size is determined. The second idea is that the mxs_nand driver can also use the databuf of struct nand_buffers instead of its own buffer for doing the DMA transfers. So we only need a small temporary buffer at the beginning to read flash ID and ONFI data. Here 256 bytes should be sufficient, this is the size of one ONFI parameter page. So in the end we only have one buffer with page+OOB size, e.g. 2048+64 bytes on a 2KB-page NAND flash instead of 36 KB. In function nand_spl_load_image() a page sized buffer is allocated and freed again before returning. This is normally no big deal, but in the early SPL stage where only a very simple version of malloc is available (the so-called MALLOC-F-Pool), buffers are only allocated but not deallocated again. Which ends up in using for example 2 KB more of the malloc space with each call. At this time, the malloc pool is located in OCRAM and is rather small, so wasting 2 KB with each call is a bad thing after all. So the third idea is to use again the databuf of struct nand_buffers here so that we do not need to allocate a new buffer each time. The function only loads full pages, so it is no problem that the main read function mxs_nand_ecc_read() uses the same buffer. In fact it means that the final memcpy() there is actually a no-op. This even speeds up the whole read process. As we do not want to break existing implementations, we add a config CONFIG_SPL_RAWNAND_BUFFERS_MALLOC and do this simplified allocation only in SPL and when this config is set. | ||||
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