Messages in this thread | | | From | "Gupta, Pekon" <> | Subject | RE: [RFC PATCH] mtd: add per NAND partition ECC config | Date | Mon, 10 Feb 2014 11:55:07 +0000 |
| |
Hi Boris,
>From: Boris BREZILLON > >This patch aims to add per partition ECC config for NAND devices. >It defines a new field in the mtd struct to store the mtd ECC config and >thus each mtd partition device can store its config instead of using the >default NAND chip config. > >This feature is needed to support the sunxi boot0 paritition case: >Allwinner boot code (BROM) requires a specific HW ECC for its boot code >that may not fit the HW NAND requirements for the entire NAND chip. > >Signed-off-by: Boris BREZILLON <b.brezillon.dev@gmail.com> >--- >Hello, > >This patch is just a draft that implement per partition ECC config. >It's currently not properly splitted (it should be separated in several >patches) and not documented either. > >There's at least one point that bother me in the current implementation: >I introduced DT notions in the nand core code by the mean of the get_ecc_ctrl >callback, and so far this was kept out of mtd/nand core code (I guess it was >on purpose). > >Please let me know if you see other drawbacks. > >If you think per partition ECC should not be implemented, could you help me >find a way to handle sunxi specific case decribed above ? > There was a discussion on having per partition based ECC earlier [1]. Though I was not in favor of supporting it earlier, but your proposal looks good. However, I still feel there are more caveats here, to explore..
[...]
>@@ -364,7 +367,13 @@ static struct mtd_part *allocate_partition(struct mtd_info *master, > slave->mtd.writesize = master->writesize; > slave->mtd.writebufsize = master->writebufsize; > slave->mtd.oobsize = master->oobsize; >- slave->mtd.oobavail = master->oobavail; >+ if (part->eccctrl) { >+ slave->mtd.eccctrl = part->eccctrl; >+ slave->mtd.oobavail = part->eccctrl->layout->oobavail; >+ } else { >+ slave->mtd.eccctrl = master->eccctrl; >+ slave->mtd.oobavail = master->oobavail; >+ } > slave->mtd.subpage_sft = master->subpage_sft; > > slave->mtd.name = name; >@@ -515,9 +524,15 @@ static struct mtd_part *allocate_partition(struct mtd_info *master, > part->name); > } > >- slave->mtd.ecclayout = master->ecclayout; >- slave->mtd.ecc_step_size = master->ecc_step_size; >- slave->mtd.ecc_strength = master->ecc_strength; >+ if (part->eccctrl) { >+ slave->mtd.ecclayout = part->eccctrl->layout; >+ slave->mtd.ecc_step_size = part->eccctrl->size; >+ slave->mtd.ecc_strength = part->eccctrl->strength;
You have to replicate 'struct nand_ecc_ctrl' from 'nand_chip' to 'mtd_info' because each ECC algorithm may have its own callback for hwctl(), calculate(), and correct(). How do you plan to populate those ? In driver probe ?
>+ } else { >+ slave->mtd.ecclayout = master->ecclayout; >+ slave->mtd.ecc_step_size = master->ecc_step_size; >+ slave->mtd.ecc_strength = master->ecc_strength; >+ } > slave->mtd.bitflip_threshold = master->bitflip_threshold; > > if (master->_block_isbad) {
[...]
>+const struct nand_ecc_ctrl *nand_get_ecc_ctrl(struct mtd_info *mtd, >+ nand_ecc_modes_t mode, >+ struct device_node *np) >+{ >+ struct nand_chip *chip = mtd->priv; >+ struct nand_ecc_ctrl *ecc; >+ u32 ecc_step, ecc_strength; >+ int ret; >+ >+ if (mode != NAND_ECC_NONE && mode != NAND_ECC_SOFT && >+ mode != NAND_ECC_SOFT_BCH) >+ return ERR_PTR(-EINVAL); >+ >+ ecc = kzalloc(sizeof(*ecc), GFP_KERNEL); >+ if (!ecc) >+ return ERR_PTR(-ENOMEM); >+ >+ ecc->size = chip->ecc_step_ds; >+ ecc->strength = chip->ecc_strength_ds; >+ if (!of_get_nand_ecc_level(np, &ecc_strength, &ecc_step)) { >+ ecc->size = ecc_step; >+ ecc->strength = ecc_strength; >+ } >+
Here we may need to ecc_strength for each partition. Example: for OMAP3 ROM supports only HAM1 (1-bit hamming), but kernel may support up-to BCH8 (8-bit BCH) ECC schemes. But, anyways that's specific to OMAP platforms..
>+ switch (mode) { >+ case NAND_ECC_NONE: >+ break; >+ case NAND_ECC_SOFT: >+ break; >+ case NAND_ECC_SOFT_BCH: >+ ecc->bytes = ((ecc->strength * fls(8 * ecc->size)) + 7) / 8; >+ break; >+ default: >+ ret = -EINVAL; >+ goto err; >+ } >+ >+ ecc->mode = mode; >+ ret = nand_ecc_ctrl_init(mtd, ecc); >+ if (ret) >+ goto err; >+ >+ ecc->release = nand_release_ecc_ctrl; >+ >+ return ecc; >+ >+err: >+ kfree(ecc); >+ return ERR_PTR(ret); >+} >+EXPORT_SYMBOL(nand_get_ecc_ctrl); >+
I'll be happy to extend and test this, if you plan a complete version.
[1] http://comments.gmane.org/gmane.linux.ports.arm.omap/108083 (you can skip initial discussion about OMAP3, and jump to Thomas Petazzoni | 2 Dec 17:19 2013)
with regards, pekon
| |