[PATCH 6/7] mtd: nand: sunxi: add support for DMA assisted operations

Boris Brezillon
2016-03-08T11:16:29Z

The sunxi NAND controller is able to pipeline ECC operations only when
operated in DMA mode, which improves a lot NAND throughput while keeping
CPU usage low.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
---
drivers/mtd/nand/sunxi_nand.c | 301 +++++++++++++++++++++++++++++++++++++++++-
1 file changed, 297 insertions(+), 4 deletions(-)

diff --git a/drivers/mtd/nand/sunxi_nand.c b/drivers/mtd/nand/sunxi_nand.c
index 07c3af7..7ba285e 100644
--- a/drivers/mtd/nand/sunxi_nand.c
+++ b/drivers/mtd/nand/sunxi_nand.c
@@ -277,6 +277,7 @@ struct sunxi_nfc {
unsigned long clk_rate;
struct list_head chips;
struct completion complete;
+ struct dma_chan *dmac;
};

static inline struct sunxi_nfc *to_sunxi_nfc(struct nand_hw_control *ctrl)
@@ -369,6 +370,68 @@ static int sunxi_nfc_rst(struct sunxi_nfc *nfc)
return ret;
}

+static int sunxi_nfc_dma_op_prepare(struct mtd_info *mtd, const void *buf,
+ int chunksize, int nchunks,
+ enum dma_data_direction ddir,
+ struct sg_table *sgt)
+{
+ struct nand_chip *nand = mtd_to_nand(mtd);
+ struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);
+ struct dma_async_tx_descriptor *dmad;
+ enum dma_transfer_direction tdir;
+ dma_cookie_t dmat;
+ int ret;
+
+ if (ddir == DMA_FROM_DEVICE)
+ tdir = DMA_DEV_TO_MEM;
+ else
+ tdir = DMA_MEM_TO_DEV;
+
+ ret = mtd_map_buf(mtd, nfc->dev, sgt, buf, nchunks * chunksize,
+ NULL, ddir);
+ if (ret)
+ return ret;
+
+ dmad = dmaengine_prep_slave_sg(nfc->dmac, sgt->sgl, sgt->nents,
+ tdir, DMA_CTRL_ACK);
+ if (IS_ERR(dmad)) {
+ ret = PTR_ERR(dmad);
+ goto err_unmap_buf;
+ }
+
+ writel(readl(nfc->regs + NFC_REG_CTL) | NFC_RAM_METHOD,
+ nfc->regs + NFC_REG_CTL);
+ writel(nchunks, nfc->regs + NFC_REG_SECTOR_NUM);
+ writel(chunksize, nfc->regs + NFC_REG_CNT);
+ dmat = dmaengine_submit(dmad);
+
+ ret = dma_submit_error(dmat);
+ if (ret)
+ goto err_clr_dma_flag;
+
+ return 0;
+
+err_clr_dma_flag:
+ writel(readl(nfc->regs + NFC_REG_CTL) & ~NFC_RAM_METHOD,
+ nfc->regs + NFC_REG_CTL);
+
+err_unmap_buf:
+ mtd_unmap_buf(mtd, nfc->dev, sgt, ddir);
+ return ret;
+}
+
+static void sunxi_nfc_dma_op_cleanup(struct mtd_info *mtd,
+ enum dma_data_direction ddir,
+ struct sg_table *sgt)
+{
+ struct nand_chip *nand = mtd_to_nand(mtd);
+ struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);
+
+ mtd_unmap_buf(mtd, nfc->dev, sgt, ddir);
+ writel(readl(nfc->regs + NFC_REG_CTL) & ~NFC_RAM_METHOD,
+ nfc->regs + NFC_REG_CTL);
+}
+
static int sunxi_nfc_dev_ready(struct mtd_info *mtd)
{
struct nand_chip *nand = mtd_to_nand(mtd);
@@ -971,6 +1034,106 @@ static void sunxi_nfc_hw_ecc_read_extra_oob(struct mtd_info *mtd,
*cur_off = mtd->oobsize + mtd->writesize;
}

+static int sunxi_nfc_hw_ecc_read_chunks_dma(struct mtd_info *mtd, uint8_t *buf,
+ int oob_required, int page,
+ int nchunks)
+{
+ struct nand_chip *nand = mtd_to_nand(mtd);
+ struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);
+ struct nand_ecc_ctrl *ecc = &nand->ecc;
+ unsigned int max_bitflips = 0;
+ int ret, i, raw_mode = 0;
+ struct sg_table sgt;
+
+ ret = sunxi_nfc_wait_cmd_fifo_empty(nfc);
+ if (ret)
+ return ret;
+
+ ret = sunxi_nfc_dma_op_prepare(mtd, buf, ecc->size, nchunks,
+ DMA_FROM_DEVICE, &sgt);
+ if (ret)
+ return ret;
+
+ sunxi_nfc_hw_ecc_enable(mtd);
+ sunxi_nfc_randomizer_config(mtd, page, false);
+ sunxi_nfc_randomizer_enable(mtd);
+
+ writel((NAND_CMD_RNDOUTSTART << 16) | (NAND_CMD_RNDOUT << 8) |
+ NAND_CMD_READSTART, nfc->regs + NFC_REG_RCMD_SET);
+
+ dma_async_issue_pending(nfc->dmac);
+
+ writel(NFC_PAGE_OP | NFC_DATA_SWAP_METHOD | NFC_DATA_TRANS,
+ nfc->regs + NFC_REG_CMD);
+
+ ret = sunxi_nfc_wait_events(nfc, NFC_CMD_INT_FLAG, true, 0);
+ if (ret)
+ dmaengine_terminate_all(nfc->dmac);
+
+ sunxi_nfc_randomizer_disable(mtd);
+ sunxi_nfc_hw_ecc_disable(mtd);
+
+ sunxi_nfc_dma_op_cleanup(mtd, DMA_FROM_DEVICE, &sgt);
+
+ if (ret)
+ return ret;
+
+ for (i = 0; i < nchunks; i++) {
+ int data_off = i * ecc->size;
+ int oob_off = i * (ecc->bytes + 4);
+ u8 *data = buf + data_off;
+ u8 *oob = nand->oob_poi + oob_off;
+ bool randomized = nand->options & NAND_NEED_SCRAMBLING;
+ bool erased;
+
+ ret = sunxi_nfc_hw_ecc_correct(mtd, randomized ? data : NULL,
+ (randomized && oob_required) ? oob : NULL,
+ i, &erased);
+ if (ret < 0) {
+ /*
+ * Re-read the data with the randomizer disabled to
+ * identify bitflips in erased pages.
+ */
+ if (nand->options & NAND_NEED_SCRAMBLING) {
+ /* TODO: use DMA to read page in raw mode */
+ nand->cmdfunc(mtd, NAND_CMD_RNDOUT,
+ data_off, -1);
+ nand->read_buf(mtd, data, ecc->size);
+ }
+
+ /* TODO: use DMA to retrieve OOB */
+ nand->cmdfunc(mtd, NAND_CMD_RNDOUT, oob_off, -1);
+ nand->read_buf(mtd, oob, ecc->bytes + 4);
+
+ ret = nand_check_erased_ecc_chunk(data, ecc->size,
+ oob, ecc->bytes + 4,
+ NULL, 0,
+ ecc->strength);
+ if (ret >= 0)
+ raw_mode = 1;
+ } else if (oob_required && !erased) {
+ /* TODO: use DMA to retrieve OOB */
+ nand->cmdfunc(mtd, NAND_CMD_RNDOUT, oob_off, -1);
+ nand->read_buf(mtd, oob, ecc->bytes + 4);
+
+ sunxi_nfc_hw_ecc_get_prot_oob_bytes(mtd, oob, i,
+ !i, page);
+ }
+
+ if (erased)
+ raw_mode = 1;
+
+ sunxi_nfc_hw_ecc_update_stats(mtd, &max_bitflips, ret);
+ }
+
+ if (oob_required)
+ sunxi_nfc_hw_ecc_read_extra_oob(mtd, nand->oob_poi,
+ NULL, !raw_mode,
+ page);
+
+ return max_bitflips;
+}
+
static int sunxi_nfc_hw_ecc_write_chunk(struct mtd_info *mtd,
const u8 *data, int data_off,
const u8 *oob, int oob_off,
@@ -1069,6 +1232,23 @@ static int sunxi_nfc_hw_ecc_read_page(struct mtd_info *mtd,
return max_bitflips;
}

+static int sunxi_nfc_hw_ecc_read_page_dma(struct mtd_info *mtd,
+ struct nand_chip *chip, u8 *buf,
+ int oob_required, int page)
+{
+ int ret;
+
+ ret = sunxi_nfc_hw_ecc_read_chunks_dma(mtd, buf, oob_required, page,
+ chip->ecc.steps);
+ if (ret >= 0)
+ return ret;
+
+ /* Fallback to PIO mode */
+ chip->cmdfunc(mtd, NAND_CMD_RNDOUT, 0, -1);
+
+ return sunxi_nfc_hw_ecc_read_page(mtd, chip, buf, oob_required, page);
+}
+
static int sunxi_nfc_hw_ecc_read_subpage(struct mtd_info *mtd,
struct nand_chip *chip,
u32 data_offs, u32 readlen,
@@ -1102,6 +1282,25 @@ static int sunxi_nfc_hw_ecc_read_subpage(struct mtd_info *mtd,
return max_bitflips;
}

+static int sunxi_nfc_hw_ecc_read_subpage_dma(struct mtd_info *mtd,
+ struct nand_chip *chip,
+ u32 data_offs, u32 readlen,
+ u8 *buf, int page)
+{
+ int nchunks = DIV_ROUND_UP(data_offs + readlen, chip->ecc.size);
+ int ret;
+
+ ret = sunxi_nfc_hw_ecc_read_chunks_dma(mtd, buf, false, page, nchunks);
+ if (ret >= 0)
+ return ret;
+
+ /* Fallback to PIO mode */
+ chip->cmdfunc(mtd, NAND_CMD_RNDOUT, 0, -1);
+
+ return sunxi_nfc_hw_ecc_read_subpage(mtd, chip, data_offs, readlen,
+ buf, page);
+}
+
static int sunxi_nfc_hw_ecc_write_page(struct mtd_info *mtd,
struct nand_chip *chip,
const uint8_t *buf, int oob_required,
@@ -1134,6 +1333,69 @@ static int sunxi_nfc_hw_ecc_write_page(struct mtd_info *mtd,
return 0;
}

+static int sunxi_nfc_hw_ecc_write_page_dma(struct mtd_info *mtd,
+ struct nand_chip *chip,
+ const u8 *buf,
+ int oob_required,
+ int page)
+{
+ struct nand_chip *nand = mtd_to_nand(mtd);
+ struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);
+ struct nand_ecc_ctrl *ecc = &nand->ecc;
+ struct sg_table sgt;
+ int ret, i;
+
+ ret = sunxi_nfc_wait_cmd_fifo_empty(nfc);
+ if (ret)
+ return ret;
+
+ ret = sunxi_nfc_dma_op_prepare(mtd, buf, ecc->size, ecc->steps,
+ DMA_TO_DEVICE, &sgt);
+ if (ret)
+ goto pio_fallback;
+
+ for (i = 0; i < ecc->steps; i++) {
+ const u8 *oob = nand->oob_poi + (i * (ecc->bytes + 4));
+
+ sunxi_nfc_hw_ecc_set_prot_oob_bytes(mtd, oob, i, !i, page);
+ }
+
+ sunxi_nfc_hw_ecc_enable(mtd);
+ sunxi_nfc_randomizer_config(mtd, page, false);
+ sunxi_nfc_randomizer_enable(mtd);
+
+ writel((NAND_CMD_RNDIN << 8) | NAND_CMD_PAGEPROG,
+ nfc->regs + NFC_REG_RCMD_SET);
+
+ dma_async_issue_pending(nfc->dmac);
+
+ writel(NFC_PAGE_OP | NFC_DATA_SWAP_METHOD |
+ NFC_DATA_TRANS | NFC_ACCESS_DIR,
+ nfc->regs + NFC_REG_CMD);
+
+ ret = sunxi_nfc_wait_events(nfc, NFC_CMD_INT_FLAG, true, 0);
+ if (ret)
+ dmaengine_terminate_all(nfc->dmac);
+
+ sunxi_nfc_randomizer_disable(mtd);
+ sunxi_nfc_hw_ecc_disable(mtd);
+
+ sunxi_nfc_dma_op_cleanup(mtd, DMA_FROM_DEVICE, &sgt);
+
+ if (ret)
+ return ret;
+
+ if (oob_required || (chip->options & NAND_NEED_SCRAMBLING))
+ /* TODO: use DMA to transfer extra OOB bytes ? */
+ sunxi_nfc_hw_ecc_write_extra_oob(mtd, chip->oob_poi,
+ NULL, page);
+
+ return 0;
+
+pio_fallback:
+ return sunxi_nfc_hw_ecc_write_page(mtd, chip, buf, oob_required, page);
+}
+
static int sunxi_nfc_hw_syndrome_ecc_read_page(struct mtd_info *mtd,
struct nand_chip *chip,
uint8_t *buf, int oob_required,
@@ -1501,6 +1763,9 @@ static int sunxi_nand_hw_ecc_ctrl_init(struct mtd_info *mtd,
struct nand_ecc_ctrl *ecc,
struct device_node *np)
{
+ struct nand_chip *nand = mtd_to_nand(mtd);
+ struct sunxi_nand_chip *sunxi_nand = to_sunxi_nand(nand);
+ struct sunxi_nfc *nfc = to_sunxi_nfc(sunxi_nand->nand.controller);
struct nand_ecclayout *layout;
int nsectors;
int i, j;
@@ -1510,11 +1775,19 @@ static int sunxi_nand_hw_ecc_ctrl_init(struct mtd_info *mtd,
if (ret)
return ret;

- ecc->read_page = sunxi_nfc_hw_ecc_read_page;
- ecc->write_page = sunxi_nfc_hw_ecc_write_page;
+ if (nfc->dmac) {
+ ecc->read_page = sunxi_nfc_hw_ecc_read_page_dma;
+ ecc->read_subpage = sunxi_nfc_hw_ecc_read_subpage_dma;
+ ecc->write_page = sunxi_nfc_hw_ecc_write_page_dma;
+ } else {
+ ecc->read_page = sunxi_nfc_hw_ecc_read_page;
+ ecc->read_subpage = sunxi_nfc_hw_ecc_read_subpage;
+ ecc->write_page = sunxi_nfc_hw_ecc_write_page;
+ }
+
+ /* TODO: support DMA for raw accesses */
ecc->read_oob_raw = nand_read_oob_std;
ecc->write_oob_raw = nand_write_oob_std;
- ecc->read_subpage = sunxi_nfc_hw_ecc_read_subpage;
layout = ecc->layout;
nsectors = mtd->writesize / ecc->size;

@@ -1888,16 +2161,34 @@ static int sunxi_nfc_probe(struct platform_device *pdev)
if (ret)
goto out_mod_clk_unprepare;

+ nfc->dmac = dma_request_slave_channel(dev, "rxtx");
+ if (nfc->dmac) {
+ struct dma_slave_config dmac_cfg = { };
+
+ dmac_cfg.src_addr = r->start + NFC_REG_IO_DATA;
+ dmac_cfg.dst_addr = dmac_cfg.src_addr;
+ dmac_cfg.src_addr_width = DMA_SLAVE_BUSWIDTH_4_BYTES;
+ dmac_cfg.dst_addr_width = dmac_cfg.src_addr_width;
+ dmac_cfg.src_maxburst = 4;
+ dmac_cfg.dst_maxburst = 4;
+ dmaengine_slave_config(nfc->dmac, &dmac_cfg);
+ } else {
+ dev_warn(dev, "failed to request rxtx DMA channel\n");
+ }
+
platform_set_drvdata(pdev, nfc);

ret = sunxi_nand_chips_init(dev, nfc);
if (ret) {
dev_err(dev, "failed to init nand chips\n");
- goto out_mod_clk_unprepare;
+ goto out_release_dmac;
}

return 0;

+out_release_dmac:
+ if (nfc->dmac)
+ dma_release_channel(nfc->dmac);
out_mod_clk_unprepare:
clk_disable_unprepare(nfc->mod_clk);
out_ahb_clk_unprepare:
@@ -1911,6 +2202,8 @@ static int sunxi_nfc_remove(struct platform_device *pdev)
struct sunxi_nfc *nfc = platform_get_drvdata(pdev);

sunxi_nand_chips_cleanup(nfc);
+ if (nfc->dmac)
+ dma_release_channel(nfc->dmac);
clk_disable_unprepare(nfc->mod_clk);
clk_disable_unprepare(nfc->ahb_clk);

--
2.1.4