[PATCH v4 2/2] mtd: nand: sunxi: Set serial access mode correctly

[Roy Spliet]

Replaces the hard coded "always use EDO" policy with that prescribed
by the ONFI 3.1 specification that EDO mode should always be used if tRC
is below 30ns.

Signed-off-by: Roy Spliet <r.spliet at ultimaker.com>

V4:
- Simplify by pre-calculating the entire timing CTL register value
---
 drivers/mtd/nand/sunxi_nand.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/drivers/mtd/nand/sunxi_nand.c b/drivers/mtd/nand/sunxi_nand.c
index 79de4ef..26df48f 100644
--- a/drivers/mtd/nand/sunxi_nand.c
+++ b/drivers/mtd/nand/sunxi_nand.c
@@ -99,6 +99,9 @@
 				 NFC_CMD_INT_ENABLE | \
 				 NFC_DMA_INT_ENABLE)
 
+/* define bit use in NFC_TIMING_CTL */
+#define NFC_TIMING_CTL_EDO	BIT(8)
+
 /* define NFC_TIMING_CFG register layout */
 #define NFC_TIMING_CFG(tWB, tADL, tWHR, tRHW, tCAD)		\
 	((tWB) & 0x3) | (((tADL) & 0x3) << 2) |			\
@@ -226,6 +229,7 @@ struct sunxi_nand_chip {
 	struct mtd_info mtd;
 	unsigned long clk_rate;
 	u32 timing_cfg;
+	u32 timing_ctl;
 	int selected;
 	int nsels;
 	struct sunxi_nand_chip_sel sels[0];
@@ -412,6 +416,7 @@ static void sunxi_nfc_select_chip(struct mtd_info *mtd, int chip)
 		}
 	}
 
+	writel(sunxi_nand->timing_ctl, nfc->regs + NFC_REG_TIMING_CTL);
 	writel(sunxi_nand->timing_cfg, nfc->regs + NFC_REG_TIMING_CFG);
 	writel(ctl, nfc->regs + NFC_REG_CTL);
 
@@ -941,6 +946,13 @@ static int sunxi_nand_chip_set_timings(struct sunxi_nand_chip *chip,
 	/* TODO: A83 has some more bits for CDQSS, CS, CLHZ, CCS, WC */
 	chip->timing_cfg = NFC_TIMING_CFG(tWB, tADL, tWHR, tRHW, tCAD);
 
+	/*
+	 * ONFI specification 3.1, paragraph 4.15.2 dictates that EDO data
+	 * output cycle timings shall be used if the host drives tRC less than
+	 * 30 ns.
+	 */
+	chip->timing_ctl = (timings->tRC_min < 30000) ? NFC_TIMING_CTL_EDO : 0;
+
 	/* Convert min_clk_period from picoseconds to nanoseconds */
 	min_clk_period = DIV_ROUND_UP(min_clk_period, 1000);
 
@@ -1442,11 +1454,6 @@ static int sunxi_nfc_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, nfc);
 
-	/*
-	 * TODO: replace this magic value with EDO flag
-	 */
-	writel(0x100, nfc->regs + NFC_REG_TIMING_CTL);
-
 	ret = sunxi_nand_chips_init(dev, nfc);
 	if (ret) {
 		dev_err(dev, "failed to init nand chips\n");
-- 
2.4.2


-- 


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