mtd: nand: sunxi: Replace failsafe timing cfg with calculated value

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 <[email protected]>

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(-)

drivers/mtd/nand/sunxi_nand.c +12 -5

index 79de4ef..26df48f 100644
@@ -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");

The TIMING_CFG register was previously statically set to a magic value (extracted from Allwinner's BSP) when initializing the NAND controller. Now that we have more details about the TIMING_CFG register layout (extracted from the A83 user manual) we can dynamically calculate the appropriate value for each NAND chip and set it when selecting the chip.

Signed-off-by Roy Spliet <[email protected]>

V2:
- Fix crippled comments

V3:
- Warn for invalid timings
- Style

V4:
- Make better use of return types
- Style and comments
- Remove superfluous initialisation

---
 drivers/mtd/nand/sunxi_nand.c | 74 ++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 69 insertions(+), 5 deletions(-)

drivers/mtd/nand/sunxi_nand.c +69 -5

index 6f93b29..79de4ef 100644
@@ -99,6 +99,13 @@
 				 NFC_CMD_INT_ENABLE | \
 				 NFC_DMA_INT_ENABLE)
 
+/* define NFC_TIMING_CFG register layout */
+#define NFC_TIMING_CFG(tWB, tADL, tWHR, tRHW, tCAD)		\
+	((tWB) & 0x3) | (((tADL) & 0x3) << 2) |			\
+	(((tWHR) & 0x3) << 4) | (((tRHW) & 0x3) << 6) |		\
+	(((tCAD) & 0x7) << 8);
+
+
 /* define bit use in NFC_CMD */
 #define NFC_CMD_LOW_BYTE	GENMASK(7, 0)
 #define NFC_CMD_HIGH_BYTE	GENMASK(15, 8)

@@ -208,6 +215,7 @@ struct sunxi_nand_hw_ecc {
  * @nand:		base NAND chip structure
  * @mtd:		base MTD structure
  * @clk_rate:		clk_rate required for this NAND chip
+ * @timing_cfg		TIMING_CFG register value for this NAND chip
  * @selected:		current active CS
  * @nsels:		number of CS lines required by the NAND chip
  * @sels:		array of CS lines descriptions

@@ -217,6 +225,7 @@ struct sunxi_nand_chip {
 	struct nand_chip nand;
 	struct mtd_info mtd;
 	unsigned long clk_rate;
+	u32 timing_cfg;
 	int selected;
 	int nsels;
 	struct sunxi_nand_chip_sel sels[0];

@@ -403,6 +412,7 @@ static void sunxi_nfc_select_chip(struct mtd_info *mtd, int chip)
 		}
 	}
 
+	writel(sunxi_nand->timing_cfg, nfc->regs + NFC_REG_TIMING_CFG);
 	writel(ctl, nfc->regs + NFC_REG_CTL);
 
 	sunxi_nand->selected = chip;

@@ -807,10 +817,33 @@ static int sunxi_nfc_hw_syndrome_ecc_write_page(struct mtd_info *mtd,
 	return 0;
 }
 
+static const s32 tWB_lut[] = {6, 12, 16, 20};
+static const s32 tRHW_lut[] = {4, 8, 12, 20};
+
+static int _sunxi_nand_lookup_timing(const s32 *lut, int lut_size, u32 duration,
+		u32 clk_period)
+{
+	u32 clk_cycles = DIV_ROUND_UP(duration, clk_period);
+	int i;
+
+	for (i = 0; i < lut_size; i++) {
+		if (clk_cycles <= lut[i])
+			return i;
+	}
+
+	/* Doesn't fit */
+	return -EINVAL;
+}
+
+#define sunxi_nand_lookup_timing(l,p,c) \
+			_sunxi_nand_lookup_timing(l, ARRAY_SIZE(l), p, c)
+
 static int sunxi_nand_chip_set_timings(struct sunxi_nand_chip *chip,
 				       const struct nand_sdr_timings *timings)
 {
+	struct sunxi_nfc *nfc = to_sunxi_nfc(chip->nand.controller);
 	u32 min_clk_period = 0;
+	u32 tWB, tADL, tWHR, tRHW, tCAD;
 
 	/* T1 <=> tCLS */
 	if (timings->tCLS_min > min_clk_period)

@@ -872,6 +905,41 @@ static int sunxi_nand_chip_set_timings(struct sunxi_nand_chip *chip,
 	if (timings->tWC_min > (min_clk_period * 2))
 		min_clk_period = DIV_ROUND_UP(timings->tWC_min, 2);
 
+	/* T16 - T19 + tCAD */
+	tWB  = sunxi_nand_lookup_timing(tWB_lut, timings->tWB_max,
+					min_clk_period);
+	if (tWB < 0) {
+		dev_err(nfc->dev, "unsupported tWB\n");
+		return tWB;
+	}
+
+	tADL = DIV_ROUND_UP(timings->tADL_min, min_clk_period) >> 3;
+	if (tADL > 3) {
+		dev_err(nfc->dev, "unsupported tADL\n");
+		return -EINVAL;
+	}
+
+	tWHR = DIV_ROUND_UP(timings->tWHR_min, min_clk_period) >> 3;
+	if (tWHR > 3) {
+		dev_err(nfc->dev, "unsupported tWHR\n");
+		return -EINVAL;
+	}
+
+	tRHW = sunxi_nand_lookup_timing(tRHW_lut, timings->tRHW_min,
+					min_clk_period);
+	if (tRHW < 0) {
+		dev_err(nfc->dev, "unsupported tRHW\n");
+		return tRHW;
+	}
+
+	/*
+	 * TODO: according to ONFI specs this value only applies for DDR NAND,
+	 * but Allwinner seems to set this to 0x7. Mimic them for now.
+	 */
+	tCAD = 0x7;
+
+	/* TODO: A83 has some more bits for CDQSS, CS, CLHZ, CCS, WC */
+	chip->timing_cfg = NFC_TIMING_CFG(tWB, tADL, tWHR, tRHW, tCAD);
 
 	/* Convert min_clk_period from picoseconds to nanoseconds */
 	min_clk_period = DIV_ROUND_UP(min_clk_period, 1000);

@@ -884,8 +952,6 @@ static int sunxi_nand_chip_set_timings(struct sunxi_nand_chip *chip,
 	 */
 	chip->clk_rate = (2 * NSEC_PER_SEC) / min_clk_period;
 
-	/* TODO: configure T16-T19 */
-
 	return 0;
 }
 

@@ -1377,11 +1443,9 @@ static int sunxi_nfc_probe(struct platform_device *pdev)
 	platform_set_drvdata(pdev, nfc);
 
 	/*
-	 * TODO: replace these magic values with proper flags as soon as we
-	 * know what they are encoding.
+	 * TODO: replace this magic value with EDO flag
 	 */
 	writel(0x100, nfc->regs + NFC_REG_TIMING_CTL);
-	writel(0x7ff, nfc->regs + NFC_REG_TIMING_CFG);
 
 	ret = sunxi_nand_chips_init(dev, nfc);
 	if (ret) {

The TIMING_CFG register was previously statically set to a magic value (extracted from Allwinner's BSP) when initializing the NAND controller. Now that we have more details about the TIMING_CFG register layout (extracted from the A83 user manual) we can dynamically calculate the appropriate value for each NAND chip and set it when selecting the chip.

Signed-off-by Roy Spliet <[email protected]>

V2:
- Fix crippled comments

V3:
- Warn for invalid timings
- Style

V4:
- Make better use of return types
- Style and comments
- Remove superfluous initialisation

---
 drivers/mtd/nand/sunxi_nand.c | 74 ++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 69 insertions(+), 5 deletions(-)

drivers/mtd/nand/sunxi_nand.c +0 -0

index 6f93b29..79de4ef 100644

drivers/mtd/nand/sunxi_nand.c +28 -0

+
+
 /* define bit use in NFC_CMD */
 #define NFC_CMD_LOW_BYTE	GENMASK(7, 0)
 #define NFC_CMD_HIGH_BYTE	GENMASK(15, 8)

@@ -208,6 +215,7 @@ struct sunxi_nand_hw_ecc {
  * @nand:		base NAND chip structure
  * @mtd:		base MTD structure
  * @clk_rate:		clk_rate required for this NAND chip
+ * @timing_cfg		TIMING_CFG register value for this NAND chip
  * @selected:		current active CS
  * @nsels:		number of CS lines required by the NAND chip
  * @sels:		array of CS lines descriptions

@@ -217,6 +225,7 @@ struct sunxi_nand_chip {
 	struct nand_chip nand;
 	struct mtd_info mtd;
 	unsigned long clk_rate;
+	u32 timing_cfg;
 	int selected;
 	int nsels;
 	struct sunxi_nand_chip_sel sels[0];

@@ -403,6 +412,7 @@ static void sunxi_nfc_select_chip(struct mtd_info *mtd, int chip)
 		}
 	}
 
+	writel(sunxi_nand->timing_cfg, nfc->regs + NFC_REG_TIMING_CFG);
 	writel(ctl, nfc->regs + NFC_REG_CTL);
 
 	sunxi_nand->selected = chip;

@@ -807,10 +817,33 @@ static int sunxi_nfc_hw_syndrome_ecc_write_page(struct mtd_info *mtd,
 	return 0;
 }
 
+static const s32 tWB_lut[] = {6, 12, 16, 20};
+static const s32 tRHW_lut[] = {4, 8, 12, 20};
+
+static int _sunxi_nand_lookup_timing(const s32 *lut, int lut_size, u32 duration,
+		u32 clk_period)
+{
+	u32 clk_cycles = DIV_ROUND_UP(duration, clk_period);
+	int i;
+
+	for (i = 0; i < lut_size; i++) {
+		if (clk_cycles <= lut[i])
+			return i;
+	}
+
+	/* Doesn't fit */
+	return -EINVAL;
+}
+
+#define sunxi_nand_lookup_timing(l,p,c) \
+			_sunxi_nand_lookup_timing(l, ARRAY_SIZE(l), p, c)
+
 static int sunxi_nand_chip_set_timings(struct sunxi_nand_chip *chip,
 				       const struct nand_sdr_timings *timings)
 {
+	struct sunxi_nfc *nfc = to_sunxi_nfc(chip->nand.controller);
 	u32 min_clk_period = 0;
+	u32 tWB, tADL, tWHR, tRHW, tCAD;
 
 	/* T1 <=> tCLS */
 	if (timings->tCLS_min > min_clk_period)

drivers/mtd/nand/sunxi_nand.c +9 -0

+		dev_err(nfc->dev, "unsupported tWB\n");
+		return tWB;
+	}
+
+	tADL = DIV_ROUND_UP(timings->tADL_min, min_clk_period) >> 3;
+	if (tADL > 3) {
+		dev_err(nfc->dev, "unsupported tADL\n");
+		return -EINVAL;
+	}

drivers/mtd/nand/sunxi_nand.c +12 -2

+		dev_err(nfc->dev, "unsupported tRHW\n");
+		return tRHW;
+	}
+
+	/*
+	 * TODO: according to ONFI specs this value only applies for DDR NAND,
+	 * but Allwinner seems to set this to 0x7. Mimic them for now.
+	 */
+	tCAD = 0x7;
+
+	/* TODO: A83 has some more bits for CDQSS, CS, CLHZ, CCS, WC */
+	chip->timing_cfg = NFC_TIMING_CFG(tWB, tADL, tWHR, tRHW, tCAD);
 
 	/* Convert min_clk_period from picoseconds to nanoseconds */
 	min_clk_period = DIV_ROUND_UP(min_clk_period, 1000);

@@ -884,8 +952,6 @@ static int sunxi_nand_chip_set_timings(struct sunxi_nand_chip *chip,
 	 */
 	chip->clk_rate = (2 * NSEC_PER_SEC) / min_clk_period;
 
-	/* TODO: configure T16-T19 */
-
 	return 0;
 }
 

@@ -1377,11 +1443,9 @@ static int sunxi_nfc_probe(struct platform_device *pdev)
 	platform_set_drvdata(pdev, nfc);