2022-05-03 01:20:00

by Chuanhong Guo

Subject: [PATCH] mtd: nand: ecc-mtk: add external ecc engine support

This adds support for using ecc-mtk as an external ECC engine.

The implemented OOB layout follows the convention to put all ECC data
at the end of OOB. As a result, the data layout is incompatible with
MTK NFI piplined ECC mode.

Signed-off-by: Chuanhong Guo <[email protected]>
---
drivers/mtd/nand/ecc-mtk.c | 335 ++++++++++++++++++++++++++++++++++++-
1 file changed, 331 insertions(+), 4 deletions(-)

diff --git a/drivers/mtd/nand/ecc-mtk.c b/drivers/mtd/nand/ecc-mtk.c
index 9f9b201fe706..998276ada671 100644
--- a/drivers/mtd/nand/ecc-mtk.c
+++ b/drivers/mtd/nand/ecc-mtk.c
@@ -15,6 +15,7 @@
#include <linux/of.h>
#include <linux/of_platform.h>
#include <linux/mutex.h>
+#include <linux/mtd/nand.h>
#include <linux/mtd/nand-ecc-mtk.h>

#define ECC_IDLE_MASK BIT(0)
@@ -26,12 +27,14 @@
#define ECC_ENCCON (0x00)
#define ECC_ENCCNFG (0x04)
#define ECC_MS_SHIFT (16)
+#define ECC_MAX_MS (8191)
#define ECC_ENCDIADDR (0x08)
#define ECC_ENCIDLE (0x0C)
#define ECC_DECCON (0x100)
#define ECC_DECCNFG (0x104)
#define DEC_EMPTY_EN BIT(31)
#define DEC_CNFG_CORRECT (0x3 << 12)
+#define ECC_DECDIADDR (0x108)
#define ECC_DECIDLE (0x10C)
#define ECC_DECENUM0 (0x114)

@@ -59,11 +62,23 @@ struct mtk_ecc {

struct completion done;
struct mutex lock;
+ struct nand_ecc_engine ecc_eng;
u32 sectors;
+ u32 refcnt;

u8 *eccdata;
};

+struct mtk_ecc_host_ctx {
+ struct mtk_ecc_config cfg;
+ struct nand_ecc_req_tweak_ctx req_ctx;
+ u8 *buf;
+ dma_addr_t buf_dma;
+ u32 free_len;
+ u32 parity_len;
+ u32 steps;
+};
+
/* ecc strength that each IP supports */
static const u8 ecc_strength_mt2701[] = {
4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 28, 32, 36,
@@ -75,6 +90,8 @@ static const u8 ecc_strength_mt2712[] = {
40, 44, 48, 52, 56, 60, 68, 72, 80
};

+static const u8 ecc_strength_mt7621[] = { 4 };
+
static const u8 ecc_strength_mt7622[] = {
4, 6, 8, 10, 12
};
@@ -115,6 +132,13 @@ static int mt7622_ecc_regs[] = {
[ECC_DECIRQ_STA] = 0x144,
};

+static struct mtk_ecc *nand_to_mtk_ecc(struct nand_device *nand)
+{
+ struct nand_ecc_engine *eng = nand->ecc.engine;
+
+ return container_of(eng, struct mtk_ecc, ecc_eng);
+}
+
static inline void mtk_ecc_wait_idle(struct mtk_ecc *ecc,
enum mtk_ecc_operation op)
{
@@ -204,6 +228,11 @@ static int mtk_ecc_config(struct mtk_ecc *ecc, struct mtk_ecc_config *config)

if (config->sectors)
ecc->sectors = 1 << (config->sectors - 1);
+
+ if (config->mode != ECC_NFI_MODE)
+ writel(lower_32_bits(config->addr),
+ ecc->regs + ECC_DECDIADDR);
+
}

return 0;
@@ -239,8 +268,14 @@ EXPORT_SYMBOL(mtk_ecc_get_stats);

void mtk_ecc_release(struct mtk_ecc *ecc)
{
- clk_disable_unprepare(ecc->clk);
- put_device(ecc->dev);
+ mutex_lock(&ecc->lock);
+
+ ecc->refcnt--;
+ if (!ecc->refcnt) {
+ clk_disable_unprepare(ecc->clk);
+ put_device(ecc->dev);
+ }
+ mutex_unlock(&ecc->lock);
}
EXPORT_SYMBOL(mtk_ecc_release);

@@ -257,6 +292,7 @@ static struct mtk_ecc *mtk_ecc_get(struct device_node *np)
{
struct platform_device *pdev;
struct mtk_ecc *ecc;
+ int ret;

pdev = of_find_device_by_node(np);
if (!pdev)
@@ -268,8 +304,17 @@ static struct mtk_ecc *mtk_ecc_get(struct device_node *np)
return ERR_PTR(-EPROBE_DEFER);
}

- clk_prepare_enable(ecc->clk);
- mtk_ecc_hw_init(ecc);
+ ret = mutex_lock_interruptible(&ecc->lock);
+ if (ret) {
+ dev_err(ecc->dev, "interrupted when attempting to lock\n");
+ return ERR_PTR(ret);
+ }
+ if (!ecc->refcnt) {
+ clk_prepare_enable(ecc->clk);
+ mtk_ecc_hw_init(ecc);
+ }
+ ecc->refcnt++;
+ mutex_unlock(&ecc->lock);

return ecc;
}
@@ -450,6 +495,283 @@ unsigned int mtk_ecc_get_parity_bits(struct mtk_ecc *ecc)
}
EXPORT_SYMBOL(mtk_ecc_get_parity_bits);

+static int mtk_ecc_host_ooblayout_ecc(struct mtd_info *mtd, int section,
+ struct mtd_oob_region *oobecc)
+{
+ struct nand_device *nand = mtd_to_nanddev(mtd);
+ struct mtk_ecc_host_ctx *ctx = nand_to_ecc_ctx(nand);
+
+ if (section)
+ return -ERANGE;
+
+ oobecc->offset = ctx->free_len + 1;
+ oobecc->length = ctx->steps * ctx->parity_len;
+ return 0;
+}
+
+static int mtk_ecc_host_ooblayout_free(struct mtd_info *mtd, int section,
+ struct mtd_oob_region *oobfree)
+{
+ struct nand_device *nand = mtd_to_nanddev(mtd);
+ struct mtk_ecc_host_ctx *ctx = nand_to_ecc_ctx(nand);
+
+ if (section)
+ return -ERANGE;
+
+ oobfree->offset = 1;
+ oobfree->length = ctx->free_len;
+ return 0;
+}
+
+static const struct mtd_ooblayout_ops mtk_ecc_host_ooblayout = {
+ .ecc = mtk_ecc_host_ooblayout_ecc,
+ .free = mtk_ecc_host_ooblayout_free,
+};
+
+static int mtk_ecc_host_init_ctx(struct nand_device *nand)
+{
+ struct mtk_ecc *ecc = nand_to_mtk_ecc(nand);
+ struct nand_ecc_props *conf = &nand->ecc.ctx.conf;
+ struct nand_ecc_props *reqs = &nand->ecc.requirements;
+ struct nand_ecc_props *user = &nand->ecc.user_conf;
+ struct mtd_info *mtd = nanddev_to_mtd(nand);
+ const u8 *ecc_strength = ecc->caps->ecc_strength;
+ int step_size = 0, strength = 0;
+ int ret = 0;
+ struct mtk_ecc_host_ctx *ctx;
+ int steps, parity_len;
+ int i;
+ u32 parity_bits;
+
+ if (user->step_size && user->strength) {
+ step_size = user->step_size;
+ strength = user->strength;
+ } else if (reqs->step_size && reqs->strength) {
+ step_size = reqs->step_size;
+ strength = reqs->strength;
+ } else {
+ dev_err(ecc->dev, "please specify a desired ECC capability.");
+ return -EINVAL;
+ }
+
+ if (step_size * 8 > ECC_MAX_MS ||
+ strength > ecc_strength[ecc->caps->num_ecc_strength - 1]) {
+ dev_err(ecc->dev, "unable to fulfill ECC capability.");
+ return -EOPNOTSUPP;
+ }
+
+ for (i = 0; i < ecc->caps->num_ecc_strength; i++) {
+ if (strength <= ecc_strength[i]) {
+ strength = ecc_strength[i];
+ break;
+ }
+ }
+
+ parity_bits = fls(1 + 8 * step_size);
+ steps = mtd->writesize / step_size;
+ parity_len = parity_bits * strength;
+ parity_len = DIV_ROUND_UP(parity_len, 8);
+
+ if (parity_len * steps > mtd->oobsize - 1) {
+ dev_err(ecc->dev, "OOB is too small for %d bytes of ECC data.",
+ parity_len * steps);
+ return -EOPNOTSUPP;
+ }
+
+ ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
+ if (!ctx)
+ return -ENOMEM;
+
+ nand->ecc.ctx.priv = ctx;
+
+ ctx->cfg.mode = ECC_DMA_MODE;
+ ctx->cfg.strength = strength;
+ ctx->cfg.sectors = 1;
+ ctx->cfg.len = step_size;
+
+ ctx->steps = steps;
+ ctx->free_len = mtd->oobsize - 1 - parity_len * steps;
+ ctx->parity_len = parity_len;
+
+ mtd_set_ooblayout(mtd, &mtk_ecc_host_ooblayout);
+ conf->step_size = step_size;
+ conf->strength = strength;
+
+ ctx->buf = dma_alloc_coherent(ecc->dev, step_size + parity_len,
+ &ctx->buf_dma, GFP_KERNEL);
+ if (!ctx->buf) {
+ ret = -ENOMEM;
+ goto free_ctx;
+ }
+ ret = nand_ecc_init_req_tweaking(&ctx->req_ctx, nand);
+ if (ret)
+ goto free_buf;
+
+ dev_info(ecc->dev, "OOB: free: %u bytes, ECC: %u bytes", ctx->free_len,
+ ctx->parity_len * ctx->steps);
+ dev_info(ecc->dev, "ECC strength: %d bits per %d bytes\n", strength,
+ step_size);
+ return 0;
+free_buf:
+ dma_free_coherent(ecc->dev, step_size + parity_len, ctx->buf,
+ ctx->buf_dma);
+free_ctx:
+ kfree(ctx);
+ return ret;
+}
+
+static void mtk_ecc_host_cleanup_ctx(struct nand_device *nand)
+{
+ struct mtk_ecc *ecc = nand_to_mtk_ecc(nand);
+ struct mtk_ecc_host_ctx *ctx = nand_to_ecc_ctx(nand);
+
+ nand_ecc_cleanup_req_tweaking(&ctx->req_ctx);
+ dma_free_coherent(ecc->dev, ctx->cfg.len + ctx->parity_len, ctx->buf,
+ ctx->buf_dma);
+ kfree(ctx);
+}
+
+static int mtk_ecc_host_prepare_io_req(struct nand_device *nand,
+ struct nand_page_io_req *req)
+{
+ struct mtk_ecc *ecc = nand_to_mtk_ecc(nand);
+ struct mtd_info *mtd = nanddev_to_mtd(nand);
+ struct mtk_ecc_host_ctx *ctx = nand_to_ecc_ctx(nand);
+ int ret, step;
+
+ if (req->mode == MTD_OPS_RAW)
+ return 0;
+
+ nand_ecc_tweak_req(&ctx->req_ctx, req);
+
+ if (req->type == NAND_PAGE_READ)
+ return 0;
+
+ ctx->cfg.op = ECC_ENCODE;
+
+ for (step = 0; step < ctx->steps; step++) {
+ ctx->cfg.addr = dma_map_single(
+ ecc->dev, (u8 *)req->databuf.out + step * ctx->cfg.len,
+ ctx->cfg.len, DMA_TO_DEVICE);
+ ret = dma_mapping_error(ecc->dev, ctx->cfg.addr);
+ if (ret) {
+ dev_err(ecc->dev, "DMA mapping failed.\n");
+ return ret;
+ }
+ ret = mtk_ecc_enable(ecc, &ctx->cfg);
+ if (ret) {
+ dma_unmap_single(ecc->dev, ctx->cfg.addr, ctx->cfg.len,
+ DMA_TO_DEVICE);
+ return ret;
+ }
+
+ ret = mtk_ecc_wait_done(ecc, ECC_ENCODE);
+ if (ret) {
+ mtk_ecc_disable(ecc);
+ dma_unmap_single(ecc->dev, ctx->cfg.addr, ctx->cfg.len,
+ DMA_TO_DEVICE);
+ return ret;
+ }
+
+ mtk_ecc_wait_idle(ecc, ECC_ENCODE);
+ dma_unmap_single(ecc->dev, ctx->cfg.addr, ctx->cfg.len,
+ DMA_TO_DEVICE);
+ __ioread32_copy(ecc->eccdata,
+ ecc->regs + ecc->caps->ecc_regs[ECC_ENCPAR00],
+ round_up(ctx->parity_len, 4));
+ mtd_ooblayout_set_eccbytes(mtd, ecc->eccdata,
+ (void *)req->oobbuf.out,
+ ctx->parity_len * step,
+ ctx->parity_len);
+ mtk_ecc_disable(ecc);
+ }
+
+ return ret;
+}
+
+static int mtk_ecc_host_finish_io_req(struct nand_device *nand,
+ struct nand_page_io_req *req)
+{
+ struct mtk_ecc *ecc = nand_to_mtk_ecc(nand);
+ struct mtd_info *mtd = nanddev_to_mtd(nand);
+ struct mtk_ecc_host_ctx *ctx = nand_to_ecc_ctx(nand);
+ u32 bitflips = 0, failed = 0;
+ int ret, step, i;
+ u32 err;
+
+ /* Nothing to do for a raw operation */
+ if (req->mode == MTD_OPS_RAW)
+ return 0;
+
+ /* This engine does not provide BBM/free OOB bytes protection */
+ if (!req->datalen)
+ return 0;
+
+ /* No more preparation for page write */
+ if (req->type == NAND_PAGE_WRITE) {
+ nand_ecc_restore_req(&ctx->req_ctx, req);
+ return 0;
+ }
+
+ ctx->cfg.op = ECC_DECODE;
+ ctx->cfg.addr = ctx->buf_dma;
+
+ for (step = 0; step < ctx->steps; step++) {
+ memcpy(ctx->buf, req->databuf.in + step * ctx->cfg.len,
+ ctx->cfg.len);
+ mtd_ooblayout_get_eccbytes(mtd, ctx->buf + ctx->cfg.len,
+ req->oobbuf.in,
+ ctx->parity_len * step,
+ ctx->parity_len);
+
+ ret = mtk_ecc_enable(ecc, &ctx->cfg);
+ if (ret)
+ break;
+
+ ret = mtk_ecc_wait_done(ecc, ECC_DECODE);
+ if (ret)
+ break;
+
+ mtk_ecc_wait_idle(ecc, ECC_DECODE);
+
+ memcpy(req->databuf.in + step * ctx->cfg.len, ctx->buf,
+ ctx->cfg.len);
+ mtd_ooblayout_set_eccbytes(mtd, ctx->buf + ctx->cfg.len,
+ req->oobbuf.in,
+ ctx->parity_len * step,
+ ctx->parity_len);
+ err = readl(ecc->regs + ECC_DECENUM0);
+ err &= ecc->caps->err_mask;
+ if (err == ecc->caps->err_mask) {
+ // skip empty page
+ for (i = 0 ; i < ctx->cfg.len + ctx->parity_len ; i++)
+ if (ctx->buf[i] != 0xff)
+ break;
+
+ if (i != ctx->cfg.len + ctx->parity_len)
+ failed++;
+ } else {
+ mtd->ecc_stats.corrected += err;
+ bitflips = max_t(u32, bitflips, err);
+ }
+
+ mtk_ecc_disable(ecc);
+ }
+
+ nand_ecc_restore_req(&ctx->req_ctx, req);
+ if (ret)
+ return ret;
+ mtd->ecc_stats.failed += failed;
+ return failed ? -EBADMSG : bitflips;
+}
+
+static struct nand_ecc_engine_ops mtk_ecc_engine_ops = {
+ .init_ctx = mtk_ecc_host_init_ctx,
+ .cleanup_ctx = mtk_ecc_host_cleanup_ctx,
+ .prepare_io_req = mtk_ecc_host_prepare_io_req,
+ .finish_io_req = mtk_ecc_host_finish_io_req,
+};
+
static const struct mtk_ecc_caps mtk_ecc_caps_mt2701 = {
.err_mask = 0x3f,
.err_shift = 8,
@@ -546,6 +868,11 @@ static int mtk_ecc_probe(struct platform_device *pdev)

ecc->dev = dev;
mutex_init(&ecc->lock);
+ ecc->ecc_eng.dev = dev;
+ ecc->ecc_eng.integration = NAND_ECC_ENGINE_INTEGRATION_EXTERNAL;
+ ecc->ecc_eng.ops = &mtk_ecc_engine_ops;
+
+ nand_ecc_register_on_host_hw_engine(&ecc->ecc_eng);
platform_set_drvdata(pdev, ecc);
dev_info(dev, "probed\n");

--
2.35.1

2022-05-04 03:26:27

by AngeloGioacchino Del Regno

Subject: Re: [PATCH] mtd: nand: ecc-mtk: add external ecc engine support

Il 30/04/22 18:40, Chuanhong Guo ha scritto:
> This adds support for using ecc-mtk as an external ECC engine.
>
> The implemented OOB layout follows the convention to put all ECC data
> at the end of OOB. As a result, the data layout is incompatible with
> MTK NFI piplined ECC mode.
>
> Signed-off-by: Chuanhong Guo <[email protected]>
> ---
> drivers/mtd/nand/ecc-mtk.c | 335 ++++++++++++++++++++++++++++++++++++-
> 1 file changed, 331 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/mtd/nand/ecc-mtk.c b/drivers/mtd/nand/ecc-mtk.c
> index 9f9b201fe706..998276ada671 100644
> --- a/drivers/mtd/nand/ecc-mtk.c
> +++ b/drivers/mtd/nand/ecc-mtk.c
> @@ -15,6 +15,7 @@
> #include <linux/of.h>
> #include <linux/of_platform.h>
> #include <linux/mutex.h>
> +#include <linux/mtd/nand.h>
> #include <linux/mtd/nand-ecc-mtk.h>
>
> #define ECC_IDLE_MASK BIT(0)
> @@ -26,12 +27,14 @@
> #define ECC_ENCCON (0x00)
> #define ECC_ENCCNFG (0x04)
> #define ECC_MS_SHIFT (16)
> +#define ECC_MAX_MS (8191)
> #define ECC_ENCDIADDR (0x08)
> #define ECC_ENCIDLE (0x0C)
> #define ECC_DECCON (0x100)
> #define ECC_DECCNFG (0x104)
> #define DEC_EMPTY_EN BIT(31)
> #define DEC_CNFG_CORRECT (0x3 << 12)
> +#define ECC_DECDIADDR (0x108)
> #define ECC_DECIDLE (0x10C)
> #define ECC_DECENUM0 (0x114)
>
> @@ -59,11 +62,23 @@ struct mtk_ecc {
>
> struct completion done;
> struct mutex lock;
> + struct nand_ecc_engine ecc_eng;
> u32 sectors;
> + u32 refcnt;

Please always use signed values for refcounts.

>
> u8 *eccdata;
> };
>
> +struct mtk_ecc_host_ctx {
> + struct mtk_ecc_config cfg;
> + struct nand_ecc_req_tweak_ctx req_ctx;
> + u8 *buf;
> + dma_addr_t buf_dma;
> + u32 free_len;
> + u32 parity_len;
> + u32 steps;
> +};
> +
> /* ecc strength that each IP supports */
> static const u8 ecc_strength_mt2701[] = {
> 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 28, 32, 36,
> @@ -75,6 +90,8 @@ static const u8 ecc_strength_mt2712[] = {
> 40, 44, 48, 52, 56, 60, 68, 72, 80
> };
>
> +static const u8 ecc_strength_mt7621[] = { 4 };
Please remove this one.

> +
> static const u8 ecc_strength_mt7622[] = {
> 4, 6, 8, 10, 12
> };
> @@ -115,6 +132,13 @@ static int mt7622_ecc_regs[] = {
> [ECC_DECIRQ_STA] = 0x144,
> };
>

..snip..

> @@ -239,8 +268,14 @@ EXPORT_SYMBOL(mtk_ecc_get_stats);
>
> void mtk_ecc_release(struct mtk_ecc *ecc)
> {
> - clk_disable_unprepare(ecc->clk);
> - put_device(ecc->dev);
> + mutex_lock(&ecc->lock);
> +
> + ecc->refcnt--;
> + if (!ecc->refcnt) {

For the sake of readability, be explicit here.

if (ecc->refcnt == 0)

...also, for safety (since we're talking about data here) it may be worth to add a

WARN((ecc->refcnt < 0), "sensible warning message here");


> + clk_disable_unprepare(ecc->clk);
> + put_device(ecc->dev);
> + }
> + mutex_unlock(&ecc->lock);
> }
> EXPORT_SYMBOL(mtk_ecc_release);
>


> +
> +static int mtk_ecc_host_init_ctx(struct nand_device *nand)
> +{
> + struct mtk_ecc *ecc = nand_to_mtk_ecc(nand);
> + struct nand_ecc_props *conf = &nand->ecc.ctx.conf;
> + struct nand_ecc_props *reqs = &nand->ecc.requirements;
> + struct nand_ecc_props *user = &nand->ecc.user_conf;
> + struct mtd_info *mtd = nanddev_to_mtd(nand);
> + const u8 *ecc_strength = ecc->caps->ecc_strength;

struct mtk_ecc_host_ctx *ctx; belongs here.

> + int step_size = 0, strength = 0;
> + int ret = 0;
> + struct mtk_ecc_host_ctx *ctx;

...not here.

> + int steps, parity_len;
> + int i;
> + u32 parity_bits;
> +

..snip..

> +
> + dev_info(ecc->dev, "OOB: free: %u bytes, ECC: %u bytes", ctx->free_len,
> + ctx->parity_len * ctx->steps);
> + dev_info(ecc->dev, "ECC strength: %d bits per %d bytes\n", strength,
> + step_size);

I'm not sure that this should really be a dev_info(), or at least not both.. as
I don't think that this is that much informative anyway.

I'd go for dev_dbg() instead.

> + return 0;
> +free_buf:
> + dma_free_coherent(ecc->dev, step_size + parity_len, ctx->buf,
> + ctx->buf_dma);
> +free_ctx:
> + kfree(ctx);
> + return ret;
> +}
> +

..snip..

> +static int mtk_ecc_host_prepare_io_req(struct nand_device *nand,
> + struct nand_page_io_req *req)
> +{
> + struct mtk_ecc *ecc = nand_to_mtk_ecc(nand);
> + struct mtd_info *mtd = nanddev_to_mtd(nand);
> + struct mtk_ecc_host_ctx *ctx = nand_to_ecc_ctx(nand);
> + int ret, step;
> +
> + if (req->mode == MTD_OPS_RAW)
> + return 0;
> +
> + nand_ecc_tweak_req(&ctx->req_ctx, req);
> +
> + if (req->type == NAND_PAGE_READ)
> + return 0;
> +
> + ctx->cfg.op = ECC_ENCODE;
> +
> + for (step = 0; step < ctx->steps; step++) {
> + ctx->cfg.addr = dma_map_single(
> + ecc->dev, (u8 *)req->databuf.out + step * ctx->cfg.len,
> + ctx->cfg.len, DMA_TO_DEVICE);
> + ret = dma_mapping_error(ecc->dev, ctx->cfg.addr);
> + if (ret) {
> + dev_err(ecc->dev, "DMA mapping failed.\n");
> + return ret;
> + }
> + ret = mtk_ecc_enable(ecc, &ctx->cfg);
> + if (ret) {
> + dma_unmap_single(ecc->dev, ctx->cfg.addr, ctx->cfg.len,
> + DMA_TO_DEVICE);
> + return ret;
> + }
> +
> + ret = mtk_ecc_wait_done(ecc, ECC_ENCODE);
> + if (ret) {
> + mtk_ecc_disable(ecc);
> + dma_unmap_single(ecc->dev, ctx->cfg.addr, ctx->cfg.len,
> + DMA_TO_DEVICE);
> + return ret;
> + }
> +
> + mtk_ecc_wait_idle(ecc, ECC_ENCODE);
> + dma_unmap_single(ecc->dev, ctx->cfg.addr, ctx->cfg.len,
> + DMA_TO_DEVICE);
> + __ioread32_copy(ecc->eccdata,
> + ecc->regs + ecc->caps->ecc_regs[ECC_ENCPAR00],
> + round_up(ctx->parity_len, 4));
> + mtd_ooblayout_set_eccbytes(mtd, ecc->eccdata,
> + (void *)req->oobbuf.out,
> + ctx->parity_len * step,
> + ctx->parity_len);
> + mtk_ecc_disable(ecc);
> + }
> +
> + return ret;

You have addressed all of the error conditions, so return 0 here.

> +}
> +
> +static int mtk_ecc_host_finish_io_req(struct nand_device *nand,
> + struct nand_page_io_req *req)
> +{
> + struct mtk_ecc *ecc = nand_to_mtk_ecc(nand);
> + struct mtd_info *mtd = nanddev_to_mtd(nand);
> + struct mtk_ecc_host_ctx *ctx = nand_to_ecc_ctx(nand);
> + u32 bitflips = 0, failed = 0;
> + int ret, step, i;

> + u32 err;

It would be more appropriate to call this variable "val" or "regval".

Also, please reorder the variables, you can do it by name...

struct mtk_ecc_host_ctx *ctx = nand_to_ecc_ctx(nand);
struct mtk_ecc *ecc = nand_to_mtk_ecc(nand);
struct mtd_info *mtd = nanddev_to_mtd(nand);
u32 bitflips = 0, failed = 0, regval;
int ret, step, i;

Please also do the same for the other instances of that.

> +
> + /* Nothing to do for a raw operation */
> + if (req->mode == MTD_OPS_RAW)
> + return 0;
> +
> + /* This engine does not provide BBM/free OOB bytes protection */
> + if (!req->datalen)
> + return 0;
> +
> + /* No more preparation for page write */
> + if (req->type == NAND_PAGE_WRITE) {
> + nand_ecc_restore_req(&ctx->req_ctx, req);
> + return 0;
> + }
> +
> + ctx->cfg.op = ECC_DECODE;
> + ctx->cfg.addr = ctx->buf_dma;
> +
> + for (step = 0; step < ctx->steps; step++) {
> + memcpy(ctx->buf, req->databuf.in + step * ctx->cfg.len,
> + ctx->cfg.len);
> + mtd_ooblayout_get_eccbytes(mtd, ctx->buf + ctx->cfg.len,
> + req->oobbuf.in,
> + ctx->parity_len * step,
> + ctx->parity_len);
> +
> + ret = mtk_ecc_enable(ecc, &ctx->cfg);
> + if (ret)
> + break;
> +
> + ret = mtk_ecc_wait_done(ecc, ECC_DECODE);
> + if (ret)

I think that you forgot to revert the enablement here; translation:
you probably forgot to call mtk_ecc_disable(ecc).
Or is there any particular and valid reason to not do that here?

If there is, you should add a comment explaining why.

> + break;
> +
> + mtk_ecc_wait_idle(ecc, ECC_DECODE);
> +
> + memcpy(req->databuf.in + step * ctx->cfg.len, ctx->buf,
> + ctx->cfg.len);

You can avoid breaking this line, as this results in 87 cols, which is fine.
Same for the other memcpy before that one, and all other instances.

> + mtd_ooblayout_set_eccbytes(mtd, ctx->buf + ctx->cfg.len,
> + req->oobbuf.in,
> + ctx->parity_len * step,
> + ctx->parity_len);
> + err = readl(ecc->regs + ECC_DECENUM0);
> + err &= ecc->caps->err_mask;
> + if (err == ecc->caps->err_mask) {
> + // skip empty page

C-style comments please. /* */


Regards,
Angelo