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authorDaniel Mack <zonque@gmail.com>2014-06-25 14:43:32 +0200
committerTom Rini <trini@ti.com>2015-01-13 11:51:23 -0500
commitc316f577b4b72d1a1aeb559e9b3fad20808f1ffd (patch)
tree9923bfbaeae9a43482ee6838dcb0cd31a7d36e6d /drivers/mtd/nand
parent92fa7f53f1f3f03296f8ffb14bdf1baefab83368 (diff)
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mtd: OMAP: Enable GPMC prefetch mode
Enable GPMC's prefetch feature for NAND access. This speeds up NAND read access a lot by pre-fetching contents in the background and reading them through the FIFO address. The current implementation has two limitations: a) it only works in 8-bit mode b) it only supports read access Both is easily fixable by someone who has hardware to implement it. Note that U-Boot code uses non word-aligned buffers to read data into, and request read lengths that are not multiples of 4, so both partial buffers (head and tail) have to be addressed. Tested on AM335x hardware. Tested-by: Guido Martínez <guido@vanguardiasur.com.ar> Reviewed-by: Guido Martínez <guido@vanguardiasur.com.ar> Signed-off-by: Daniel Mack <zonque@gmail.com> [trini: Make apply again, use 'cs' fix pointed out by Guido] Signed-off-by: Tom Rini <trini@ti.com>
Diffstat (limited to 'drivers/mtd/nand')
-rw-r--r--drivers/mtd/nand/omap_gpmc.c114
1 files changed, 112 insertions, 2 deletions
diff --git a/drivers/mtd/nand/omap_gpmc.c b/drivers/mtd/nand/omap_gpmc.c
index 459904d..fc64f48 100644
--- a/drivers/mtd/nand/omap_gpmc.c
+++ b/drivers/mtd/nand/omap_gpmc.c
@@ -441,6 +441,115 @@ static int omap_correct_data_bch(struct mtd_info *mtd, uint8_t *dat,
return (err) ? err : error_count;
}
+#ifdef CONFIG_NAND_OMAP_GPMC_PREFETCH
+
+#define PREFETCH_CONFIG1_CS_SHIFT 24
+#define PREFETCH_FIFOTHRESHOLD_MAX 0x40
+#define PREFETCH_FIFOTHRESHOLD(val) ((val) << 8)
+#define PREFETCH_STATUS_COUNT(val) (val & 0x00003fff)
+#define PREFETCH_STATUS_FIFO_CNT(val) ((val >> 24) & 0x7F)
+#define ENABLE_PREFETCH (1 << 7)
+
+/**
+ * omap_prefetch_enable - configures and starts prefetch transfer
+ * @fifo_th: fifo threshold to be used for read/ write
+ * @count: number of bytes to be transferred
+ * @is_write: prefetch read(0) or write post(1) mode
+ * @cs: chip select to use
+ */
+static int omap_prefetch_enable(int fifo_th, unsigned int count, int is_write, int cs)
+{
+ uint32_t val;
+
+ if (fifo_th > PREFETCH_FIFOTHRESHOLD_MAX)
+ return -EINVAL;
+
+ if (readl(&gpmc_cfg->prefetch_control))
+ return -EBUSY;
+
+ /* Set the amount of bytes to be prefetched */
+ writel(count, &gpmc_cfg->prefetch_config2);
+
+ val = (cs << PREFETCH_CONFIG1_CS_SHIFT) | (is_write & 1) |
+ PREFETCH_FIFOTHRESHOLD(fifo_th) | ENABLE_PREFETCH;
+ writel(val, &gpmc_cfg->prefetch_config1);
+
+ /* Start the prefetch engine */
+ writel(1, &gpmc_cfg->prefetch_control);
+
+ return 0;
+}
+
+/**
+ * omap_prefetch_reset - disables and stops the prefetch engine
+ */
+static void omap_prefetch_reset(void)
+{
+ writel(0, &gpmc_cfg->prefetch_control);
+ writel(0, &gpmc_cfg->prefetch_config1);
+}
+
+static int __read_prefetch_aligned(struct nand_chip *chip, uint32_t *buf, int len)
+{
+ int ret;
+ uint32_t cnt;
+ struct omap_nand_info *info = chip->priv;
+
+ ret = omap_prefetch_enable(PREFETCH_FIFOTHRESHOLD_MAX, len, 0, info->cs);
+ if (ret < 0)
+ return ret;
+
+ do {
+ int i;
+
+ cnt = readl(&gpmc_cfg->prefetch_status);
+ cnt = PREFETCH_STATUS_FIFO_CNT(cnt);
+
+ for (i = 0; i < cnt / 4; i++) {
+ *buf++ = readl(CONFIG_SYS_NAND_BASE);
+ len -= 4;
+ }
+ } while (len);
+
+ omap_prefetch_reset();
+
+ return 0;
+}
+
+static void omap_nand_read_prefetch8(struct mtd_info *mtd, uint8_t *buf, int len)
+{
+ int ret;
+ uint32_t head, tail;
+ struct nand_chip *chip = mtd->priv;
+
+ /*
+ * If the destination buffer is unaligned, start with reading
+ * the overlap byte-wise.
+ */
+ head = ((uint32_t) buf) % 4;
+ if (head) {
+ nand_read_buf(mtd, buf, head);
+ buf += head;
+ len -= head;
+ }
+
+ /*
+ * Only transfer multiples of 4 bytes in a pre-fetched fashion.
+ * If there's a residue, care for it byte-wise afterwards.
+ */
+ tail = len % 4;
+
+ ret = __read_prefetch_aligned(chip, (uint32_t *) buf, len - tail);
+ if (ret < 0) {
+ /* fallback in case the prefetch engine is busy */
+ nand_read_buf(mtd, buf, len);
+ } else if (tail) {
+ buf += len - tail;
+ nand_read_buf(mtd, buf, tail);
+ }
+}
+#endif /* CONFIG_NAND_OMAP_GPMC_PREFETCH */
+
/**
* omap_read_page_bch - hardware ecc based page read function
* @mtd: mtd info structure
@@ -880,11 +989,12 @@ int board_nand_init(struct nand_chip *nand)
if (err)
return err;
-#ifdef CONFIG_SPL_BUILD
+#ifdef CONFIG_NAND_OMAP_GPMC_PREFETCH
+ /* TODO: Implement for 16-bit bus width */
if (nand->options & NAND_BUSWIDTH_16)
nand->read_buf = nand_read_buf16;
else
- nand->read_buf = nand_read_buf;
+ nand->read_buf = omap_nand_read_prefetch8;
#endif
nand->dev_ready = omap_dev_ready;