[PATCH v2 0/3] mtd: nand: add randomizer support

[PATCH v2 0/3] mtd: nand: add randomizer support

[Boris Brezillon]

Hello,

This series is a proposal to add support for randomizers (either software
or hardware) to NAND flash controller drivers.

The last patch is the sunxi HW randomizer implementation and is just given
as an example (it won't apply on the MTD tree, because it depends on other
stuff not yet posted on the MTD ML, but if you want a full overview of the
NAND Flash controller driver you can take a look at this series [2]).

I can also provide a software implementation based on LFSR (Left Feedback
Shift Register) algorithm, thought I haven't tested it yet, hence why it's
not part of this series. Let me know if you're interested in this
implementation.

This series depends on the "per-partition ECC" series [1], because I need
the randomizer seed to be different depending on the partition (for the
same reason I needed ECC config to be different for each partition: the
bootrom config might not fit the NAND chip requirements).

I'd like to have feedback from both MTD maintainers and driver
developers who might need to implement (or use) a randomizer in their
system, so feel free to comment on this series.

Best Regards,

Boris

[1] https://lkml.org/lkml/2014/2/12/627
[2] https://groups.google.com/forum/#!msg/linux-sunxi/s3lBb01I0Js/z2NoCFJ83g4J 

Changes since v1:
- add some comments to explain how the sunxi randomizer works
- fix a few minor bugs and coding style issues

Boris Brezillon (3):
  mtd: nand: add NAND_NEED_SCRAMBLING option flag
  mtd: nand: add NAND_NEED_SCRAMBLING flag to the H27UCG8T2ATR-BC
    definition
  mtd: nand: sunxi: add randomizer support

 drivers/mtd/nand/nand_ids.c   |   4 +-
 drivers/mtd/nand/sunxi_nand.c | 287 ++++++++++++++++++++++++++++++++++++++----
 include/linux/mtd/nand.h      |   6 +
 3 files changed, 269 insertions(+), 28 deletions(-)

-- 
2.1.4

[PATCH v2 0/3] mtd: nand: add randomizer support

[Boris Brezillon]

Hello,

This series is a proposal to add support for randomizers (either software
or hardware) to NAND flash controller drivers.

The last patch is the sunxi HW randomizer implementation and is just given
as an example (it won't apply on the MTD tree, because it depends on other
stuff not yet posted on the MTD ML, but if you want a full overview of the
NAND Flash controller driver you can take a look at this series [2]).

I can also provide a software implementation based on LFSR (Left Feedback
Shift Register) algorithm, thought I haven't tested it yet, hence why it's
not part of this series. Let me know if you're interested in this
implementation.

This series depends on the "per-partition ECC" series [1], because I need
the randomizer seed to be different depending on the partition (for the
same reason I needed ECC config to be different for each partition: the
bootrom config might not fit the NAND chip requirements).

I'd like to have feedback from both MTD maintainers and driver
developers who might need to implement (or use) a randomizer in their
system, so feel free to comment on this series.

Best Regards,

Boris

[1] https://lkml.org/lkml/2014/2/12/627
[2] https://groups.google.com/forum/#!msg/linux-sunxi/s3lBb01I0Js/z2NoCFJ83g4J 

Changes since v1:
- add some comments to explain how the sunxi randomizer works
- fix a few minor bugs and coding style issues

Boris Brezillon (3):
  mtd: nand: add NAND_NEED_SCRAMBLING option flag
  mtd: nand: add NAND_NEED_SCRAMBLING flag to the H27UCG8T2ATR-BC
    definition
  mtd: nand: sunxi: add randomizer support

 drivers/mtd/nand/nand_ids.c   |   4 +-
 drivers/mtd/nand/sunxi_nand.c | 287 ++++++++++++++++++++++++++++++++++++++----
 include/linux/mtd/nand.h      |   6 +
 3 files changed, 269 insertions(+), 28 deletions(-)

-- 
2.1.4

[PATCH v2 1/3] mtd: nand: add NAND_NEED_SCRAMBLING option flag

[Boris Brezillon]

Some MLC NANDs are sensitive to repeated patterns and require data to be
scrambled in order to limit the number of bitflips.
Add a new flag to let the NAND controller know about this constraint.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
---
 include/linux/mtd/nand.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
index fad634e..0203b15 100644
--- a/include/linux/mtd/nand.h
+++ b/include/linux/mtd/nand.h
@@ -160,6 +160,12 @@ typedef enum {
 /* Device supports subpage reads */
 #define NAND_SUBPAGE_READ	0x00001000
 
+/*
+ * Some MLC NANDs need data scrambling to limit bitflips caused by repeated
+ * patterns.
+ */
+#define NAND_NEED_SCRAMBLING	0x00002000
+
 /* Options valid for Samsung large page devices */
 #define NAND_SAMSUNG_LP_OPTIONS NAND_CACHEPRG
 
-- 
2.1.4

[PATCH v2 1/3] mtd: nand: add NAND_NEED_SCRAMBLING option flag

[Boris Brezillon]

Some MLC NANDs are sensitive to repeated patterns and require data to be
scrambled in order to limit the number of bitflips.
Add a new flag to let the NAND controller know about this constraint.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
---
 include/linux/mtd/nand.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
index fad634e..0203b15 100644
--- a/include/linux/mtd/nand.h
+++ b/include/linux/mtd/nand.h
@@ -160,6 +160,12 @@ typedef enum {
 /* Device supports subpage reads */
 #define NAND_SUBPAGE_READ	0x00001000
 
+/*
+ * Some MLC NANDs need data scrambling to limit bitflips caused by repeated
+ * patterns.
+ */
+#define NAND_NEED_SCRAMBLING	0x00002000
+
 /* Options valid for Samsung large page devices */
 #define NAND_SAMSUNG_LP_OPTIONS NAND_CACHEPRG
 
-- 
2.1.4

[PATCH v2 2/3] mtd: nand: add NAND_NEED_SCRAMBLING flag to the H27UCG8T2ATR-BC definition

[Boris Brezillon]

The H27UCG8T2ATR-BC requires an external data scrambler. Reflect this
constraint in the nand_flash_ids definition.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
---
 drivers/mtd/nand/nand_ids.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/nand/nand_ids.c b/drivers/mtd/nand/nand_ids.c
index a8804a3..ccc05f5 100644
--- a/drivers/mtd/nand/nand_ids.c
+++ b/drivers/mtd/nand/nand_ids.c
@@ -50,8 +50,8 @@ struct nand_flash_dev nand_flash_ids[] = {
 		  SZ_16K, SZ_8K, SZ_4M, 0, 6, 1280, NAND_ECC_INFO(40, SZ_1K) },
 	{"H27UCG8T2ATR-BC 64G 3.3V 8-bit",
 		{ .id = {0xad, 0xde, 0x94, 0xda, 0x74, 0xc4} },
-		  SZ_8K, SZ_8K, SZ_2M, 0, 6, 640, NAND_ECC_INFO(40, SZ_1K),
-		  4 },
+		  SZ_8K, SZ_8K, SZ_2M, NAND_NEED_SCRAMBLING, 6, 640,
+		  NAND_ECC_INFO(40, SZ_1K), 4 },
 
 	LEGACY_ID_NAND("NAND 4MiB 5V 8-bit",   0x6B, 4, SZ_8K, SP_OPTIONS),
 	LEGACY_ID_NAND("NAND 4MiB 3,3V 8-bit", 0xE3, 4, SZ_8K, SP_OPTIONS),
-- 
2.1.4

[PATCH v2 2/3] mtd: nand: add NAND_NEED_SCRAMBLING flag to the H27UCG8T2ATR-BC definition

[Boris Brezillon]

The H27UCG8T2ATR-BC requires an external data scrambler. Reflect this
constraint in the nand_flash_ids definition.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
---
 drivers/mtd/nand/nand_ids.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/nand/nand_ids.c b/drivers/mtd/nand/nand_ids.c
index a8804a3..ccc05f5 100644
--- a/drivers/mtd/nand/nand_ids.c
+++ b/drivers/mtd/nand/nand_ids.c
@@ -50,8 +50,8 @@ struct nand_flash_dev nand_flash_ids[] = {
 		  SZ_16K, SZ_8K, SZ_4M, 0, 6, 1280, NAND_ECC_INFO(40, SZ_1K) },
 	{"H27UCG8T2ATR-BC 64G 3.3V 8-bit",
 		{ .id = {0xad, 0xde, 0x94, 0xda, 0x74, 0xc4} },
-		  SZ_8K, SZ_8K, SZ_2M, 0, 6, 640, NAND_ECC_INFO(40, SZ_1K),
-		  4 },
+		  SZ_8K, SZ_8K, SZ_2M, NAND_NEED_SCRAMBLING, 6, 640,
+		  NAND_ECC_INFO(40, SZ_1K), 4 },
 
 	LEGACY_ID_NAND("NAND 4MiB 5V 8-bit",   0x6B, 4, SZ_8K, SP_OPTIONS),
 	LEGACY_ID_NAND("NAND 4MiB 3,3V 8-bit", 0xE3, 4, SZ_8K, SP_OPTIONS),
-- 
2.1.4

[PATCH v2 3/3] mtd: nand: sunxi: add randomizer support

[Boris Brezillon]

Add support for the randomizer engine available in Allwinner's NFC IP.

Randomization is useful to support modern NAND chips which are sensitive to
repeated patterns. On such NANDs you might experience an unexpectedly high
number of bitflips when you repeat the same pattern all over a given NAND
block.
Randomizing input data mitigate this problem by avoiding such repeated
patterns.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
---
 drivers/mtd/nand/sunxi_nand.c | 287 ++++++++++++++++++++++++++++++++++++++----
 1 file changed, 261 insertions(+), 26 deletions(-)

diff --git a/drivers/mtd/nand/sunxi_nand.c b/drivers/mtd/nand/sunxi_nand.c
index 1bbcc0c..43f25327f 100644
--- a/drivers/mtd/nand/sunxi_nand.c
+++ b/drivers/mtd/nand/sunxi_nand.c
@@ -60,6 +60,7 @@
 #define NFC_REG_ECC_ERR_CNT(x)	((0x0040 + (x)) & ~0x3)
 #define NFC_REG_USER_DATA(x)	(0x0050 + ((x) * 4))
 #define NFC_REG_SPARE_AREA	0x00A0
+#define NFC_REG_PAT_ID		0x00A4
 #define NFC_RAM0_BASE		0x0400
 #define NFC_RAM1_BASE		0x0800
 
@@ -539,6 +540,174 @@ static void sunxi_nfc_cmd_ctrl(struct mtd_info *mtd, int dat,
 	sunxi_nfc_wait_int(nfc, NFC_CMD_INT_FLAG, 0);
 }
 
+/* These seed values have been extracted from Allwinner's BSP */
+static const u16 sunxi_nfc_randomizer_page_seeds[] = {
+	0x2b75, 0x0bd0, 0x5ca3, 0x62d1, 0x1c93, 0x07e9, 0x2162, 0x3a72,
+	0x0d67, 0x67f9, 0x1be7, 0x077d, 0x032f, 0x0dac, 0x2716, 0x2436,
+	0x7922, 0x1510, 0x3860, 0x5287, 0x480f, 0x4252, 0x1789, 0x5a2d,
+	0x2a49, 0x5e10, 0x437f, 0x4b4e, 0x2f45, 0x216e, 0x5cb7, 0x7130,
+	0x2a3f, 0x60e4, 0x4dc9, 0x0ef0, 0x0f52, 0x1bb9, 0x6211, 0x7a56,
+	0x226d, 0x4ea7, 0x6f36, 0x3692, 0x38bf, 0x0c62, 0x05eb, 0x4c55,
+	0x60f4, 0x728c, 0x3b6f, 0x2037, 0x7f69, 0x0936, 0x651a, 0x4ceb,
+	0x6218, 0x79f3, 0x383f, 0x18d9, 0x4f05, 0x5c82, 0x2912, 0x6f17,
+	0x6856, 0x5938, 0x1007, 0x61ab, 0x3e7f, 0x57c2, 0x542f, 0x4f62,
+	0x7454, 0x2eac, 0x7739, 0x42d4, 0x2f90, 0x435a, 0x2e52, 0x2064,
+	0x637c, 0x66ad, 0x2c90, 0x0bad, 0x759c, 0x0029, 0x0986, 0x7126,
+	0x1ca7, 0x1605, 0x386a, 0x27f5, 0x1380, 0x6d75, 0x24c3, 0x0f8e,
+	0x2b7a, 0x1418, 0x1fd1, 0x7dc1, 0x2d8e, 0x43af, 0x2267, 0x7da3,
+	0x4e3d, 0x1338, 0x50db, 0x454d, 0x764d, 0x40a3, 0x42e6, 0x262b,
+	0x2d2e, 0x1aea, 0x2e17, 0x173d, 0x3a6e, 0x71bf, 0x25f9, 0x0a5d,
+	0x7c57, 0x0fbe, 0x46ce, 0x4939, 0x6b17, 0x37bb, 0x3e91, 0x76db,
+};
+
+/*
+ * sunxi_nfc_randomizer_ecc512_seeds and sunxi_nfc_randomizer_ecc1024_seeds
+ * have been generated using
+ * sunxi_nfc_randomizer_step(seed, (step_size * 8) + 15), which is what
+ * the randomizer engine does internally before de/scrambling OOB data.
+ *
+ * Those tables are statically defined to avoid calculating randomizer state
+ * at runtime.
+ */
+static const u16 sunxi_nfc_randomizer_ecc512_seeds[] = {
+	0x3346, 0x367f, 0x1f18, 0x769a, 0x4f64, 0x068c, 0x2ef1, 0x6b64,
+	0x28a9, 0x15d7, 0x30f8, 0x3659, 0x53db, 0x7c5f, 0x71d4, 0x4409,
+	0x26eb, 0x03cc, 0x655d, 0x47d4, 0x4daa, 0x0877, 0x712d, 0x3617,
+	0x3264, 0x49aa, 0x7f9e, 0x588e, 0x4fbc, 0x7176, 0x7f91, 0x6c6d,
+	0x4b95, 0x5fb7, 0x3844, 0x4037, 0x0184, 0x081b, 0x0ee8, 0x5b91,
+	0x293d, 0x1f71, 0x0e6f, 0x402b, 0x5122, 0x1e52, 0x22be, 0x3d2d,
+	0x75bc, 0x7c60, 0x6291, 0x1a2f, 0x61d4, 0x74aa, 0x4140, 0x29ab,
+	0x472d, 0x2852, 0x017e, 0x15e8, 0x5ec2, 0x17cf, 0x7d0f, 0x06b8,
+	0x117a, 0x6b94, 0x789b, 0x3126, 0x6ac5, 0x5be7, 0x150f, 0x51f8,
+	0x7889, 0x0aa5, 0x663d, 0x77e8, 0x0b87, 0x3dcb, 0x360d, 0x218b,
+	0x512f, 0x7dc9, 0x6a4d, 0x630a, 0x3547, 0x1dd2, 0x5aea, 0x69a5,
+	0x7bfa, 0x5e4f, 0x1519, 0x6430, 0x3a0e, 0x5eb3, 0x5425, 0x0c7a,
+	0x5540, 0x3670, 0x63c1, 0x31e9, 0x5a39, 0x2de7, 0x5979, 0x2891,
+	0x1562, 0x014b, 0x5b05, 0x2756, 0x5a34, 0x13aa, 0x6cb5, 0x2c36,
+	0x5e72, 0x1306, 0x0861, 0x15ef, 0x1ee8, 0x5a37, 0x7ac4, 0x45dd,
+	0x44c4, 0x7266, 0x2f41, 0x3ccc, 0x045e, 0x7d40, 0x7c66, 0x0fa0,
+};
+
+static const u16 sunxi_nfc_randomizer_ecc1024_seeds[] = {
+	0x2cf5, 0x35f1, 0x63a4, 0x5274, 0x2bd2, 0x778b, 0x7285, 0x32b6,
+	0x6a5c, 0x70d6, 0x757d, 0x6769, 0x5375, 0x1e81, 0x0cf3, 0x3982,
+	0x6787, 0x042a, 0x6c49, 0x1925, 0x56a8, 0x40a9, 0x063e, 0x7bd9,
+	0x4dbf, 0x55ec, 0x672e, 0x7334, 0x5185, 0x4d00, 0x232a, 0x7e07,
+	0x445d, 0x6b92, 0x528f, 0x4255, 0x53ba, 0x7d82, 0x2a2e, 0x3a4e,
+	0x75eb, 0x450c, 0x6844, 0x1b5d, 0x581a, 0x4cc6, 0x0379, 0x37b2,
+	0x419f, 0x0e92, 0x6b27, 0x5624, 0x01e3, 0x07c1, 0x44a5, 0x130c,
+	0x13e8, 0x5910, 0x0876, 0x60c5, 0x54e3, 0x5b7f, 0x2269, 0x509f,
+	0x7665, 0x36fd, 0x3e9a, 0x0579, 0x6295, 0x14ef, 0x0a81, 0x1bcc,
+	0x4b16, 0x64db, 0x0514, 0x4f07, 0x0591, 0x3576, 0x6853, 0x0d9e,
+	0x259f, 0x38b7, 0x64fb, 0x3094, 0x4693, 0x6ddd, 0x29bb, 0x0bc8,
+	0x3f47, 0x490e, 0x0c0e, 0x7933, 0x3c9e, 0x5840, 0x398d, 0x3e68,
+	0x4af1, 0x71f5, 0x57cf, 0x1121, 0x64eb, 0x3579, 0x15ac, 0x584d,
+	0x5f2a, 0x47e2, 0x6528, 0x6eac, 0x196e, 0x6b96, 0x0450, 0x0179,
+	0x609c, 0x06e1, 0x4626, 0x42c7, 0x273e, 0x486f, 0x0705, 0x1601,
+	0x145b, 0x407e, 0x062b, 0x57a5, 0x53f9, 0x5659, 0x4410, 0x3ccd,
+};
+
+static u16 sunxi_nfc_randomizer_step(u16 state, int count)
+{
+	state &= 0x7fff;
+
+	/*
+	 * This loop is just a simple implementation of a Fibonacci LFSR using
+	 * the x16 + x15 + 1 polynomial.
+	 */
+	while (count--)
+		state = ((state >> 1) |
+			 (((state ^ (state >> 1)) & 1) << 14)) & 0x7fff;
+
+	return state;
+}
+
+static u16 sunxi_nfc_randomizer_state(struct mtd_info *mtd, int page, bool ecc)
+{
+	const u16 *seeds = sunxi_nfc_randomizer_page_seeds;
+	int mod = mtd->erasesize / mtd->writesize;
+
+	if (mod > ARRAY_SIZE(sunxi_nfc_randomizer_page_seeds))
+		mod = ARRAY_SIZE(sunxi_nfc_randomizer_page_seeds);
+
+	if (ecc) {
+		if (mtd->ecc_step_size == 512)
+			seeds = sunxi_nfc_randomizer_ecc512_seeds;
+		else
+			seeds = sunxi_nfc_randomizer_ecc1024_seeds;
+	}
+
+	return seeds[page % mod];
+}
+
+static void sunxi_nfc_randomizer_config(struct mtd_info *mtd,
+					int page, bool ecc)
+{
+	struct nand_chip *nand = mtd->priv;
+	struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);
+	u32 ecc_ctl = readl(nfc->regs + NFC_REG_ECC_CTL);
+	u16 state;
+
+	if (!(nand->options & NAND_NEED_SCRAMBLING))
+		return;
+
+	ecc_ctl = readl(nfc->regs + NFC_REG_ECC_CTL);
+	state = sunxi_nfc_randomizer_state(mtd, page, ecc);
+	ecc_ctl = readl(nfc->regs + NFC_REG_ECC_CTL) & ~NFC_RANDOM_SEED_MSK;
+	writel(ecc_ctl | NFC_RANDOM_SEED(state), nfc->regs + NFC_REG_ECC_CTL);
+}
+
+static void sunxi_nfc_randomizer_enable(struct mtd_info *mtd)
+{
+	struct nand_chip *nand = mtd->priv;
+	struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);
+
+	if (!(nand->options & NAND_NEED_SCRAMBLING))
+		return;
+
+	writel(readl(nfc->regs + NFC_REG_ECC_CTL) | NFC_RANDOM_EN,
+	       nfc->regs + NFC_REG_ECC_CTL);
+}
+
+static void sunxi_nfc_randomizer_disable(struct mtd_info *mtd)
+{
+	struct nand_chip *nand = mtd->priv;
+	struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);
+
+	if (!(nand->options & NAND_NEED_SCRAMBLING))
+		return;
+
+	writel(readl(nfc->regs + NFC_REG_ECC_CTL) & ~NFC_RANDOM_EN,
+	       nfc->regs + NFC_REG_ECC_CTL);
+}
+
+static void sunxi_nfc_randomize_bbm(struct mtd_info *mtd, int page, u8 *bbm)
+{
+	u16 state = sunxi_nfc_randomizer_state(mtd, page, true);
+
+	bbm[0] ^= state;
+	bbm[1] ^= sunxi_nfc_randomizer_step(state, 8);
+}
+
+static void sunxi_nfc_randomizer_write_buf(struct mtd_info *mtd,
+					   const uint8_t *buf, int len,
+					   bool ecc, int page)
+{
+	sunxi_nfc_randomizer_config(mtd, page, ecc);
+	sunxi_nfc_randomizer_enable(mtd);
+	sunxi_nfc_write_buf(mtd, buf, len);
+	sunxi_nfc_randomizer_disable(mtd);
+}
+
+static void sunxi_nfc_randomizer_read_buf(struct mtd_info *mtd, uint8_t *buf,
+					  int len, bool ecc, int page)
+{
+	sunxi_nfc_randomizer_config(mtd, page, ecc);
+	sunxi_nfc_randomizer_enable(mtd);
+	sunxi_nfc_read_buf(mtd, buf, len);
+	sunxi_nfc_randomizer_disable(mtd);
+}
+
 static void sunxi_nfc_hw_ecc_enable(struct mtd_info *mtd)
 {
 	struct nand_chip *nand = mtd->priv;
@@ -575,18 +744,20 @@ static int sunxi_nfc_hw_ecc_read_chunk(struct mtd_info *mtd,
 				       u8 *data, int data_off,
 				       u8 *oob, int oob_off,
 				       int *cur_off,
-				       unsigned int *max_bitflips)
+				       unsigned int *max_bitflips,
+				       bool bbm, int page)
 {
 	struct nand_chip *nand = mtd->priv;
 	struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);
 	struct nand_ecc_ctrl *ecc = &nand->ecc;
+	int raw_mode = 0;
 	u32 status;
 	int ret;
 
 	if (*cur_off != data_off)
 		nand->cmdfunc(mtd, NAND_CMD_RNDOUT, data_off, -1);
 
-	sunxi_nfc_read_buf(mtd, NULL, ecc->size);
+	sunxi_nfc_randomizer_read_buf(mtd, NULL, ecc->size, false, page);
 
 	if (data_off + ecc->size != oob_off)
 		nand->cmdfunc(mtd, NAND_CMD_RNDOUT, oob_off, -1);
@@ -595,25 +766,54 @@ static int sunxi_nfc_hw_ecc_read_chunk(struct mtd_info *mtd,
 	if (ret)
 		return ret;
 
+	sunxi_nfc_randomizer_enable(mtd);
 	writel(NFC_DATA_TRANS | NFC_DATA_SWAP_METHOD | NFC_ECC_OP,
 	       nfc->regs + NFC_REG_CMD);
 
 	ret = sunxi_nfc_wait_int(nfc, NFC_CMD_INT_FLAG, 0);
+	sunxi_nfc_randomizer_disable(mtd);
 	if (ret)
 		return ret;
 
+	*cur_off = oob_off + ecc->bytes + 4;
+
 	status = readl(nfc->regs + NFC_REG_ECC_ST);
+	if (status & NFC_ECC_PAT_FOUND(0)) {
+		u8 pattern = 0xff;
+
+		if (unlikely(!(readl(nfc->regs + NFC_REG_PAT_ID) & 0x1)))
+			pattern = 0x0;
+
+		memset(data, pattern, ecc->size);
+		memset(oob, pattern, ecc->bytes + 4);
+
+		return 1;
+	}
+
 	ret = NFC_ECC_ERR_CNT(0, readl(nfc->regs + NFC_REG_ECC_ERR_CNT(0)));
 
 	memcpy_fromio(data, nfc->regs + NFC_RAM0_BASE, ecc->size);
 
 	nand->cmdfunc(mtd, NAND_CMD_RNDOUT, oob_off, -1);
-	sunxi_nfc_read_buf(mtd, oob, ecc->bytes + 4);
+	sunxi_nfc_randomizer_read_buf(mtd, oob, ecc->bytes + 4, true, page);
 
 	if (status & NFC_ECC_ERR(0)) {
+		/*
+		 * Re-read the data with the randomizer disabled to identify
+		 * bitflips in erased pages.
+		 */
+		if (nand->options & NAND_NEED_SCRAMBLING) {
+			nand->cmdfunc(mtd, NAND_CMD_RNDOUT, data_off, -1);
+			nand->read_buf(mtd, data, ecc->size);
+			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 {
 		/*
 		 * The engine protects 4 bytes of OOB data per chunk.
@@ -621,6 +821,10 @@ static int sunxi_nfc_hw_ecc_read_chunk(struct mtd_info *mtd,
 		 */
 		sunxi_nfc_user_data_to_buf(readl(nfc->regs + NFC_REG_USER_DATA(0)),
 					   oob);
+
+		/* De-randomize the Bad Block Marker. */
+		if (bbm && nand->options & NAND_NEED_SCRAMBLING)
+			sunxi_nfc_randomize_bbm(mtd, page, oob);
 	}
 
 	if (ret < 0) {
@@ -630,13 +834,12 @@ static int sunxi_nfc_hw_ecc_read_chunk(struct mtd_info *mtd,
 		*max_bitflips = max_t(unsigned int, *max_bitflips, ret);
 	}
 
-	*cur_off = oob_off + ecc->bytes + 4;
-
-	return 0;
+	return raw_mode;
 }
 
 static void sunxi_nfc_hw_ecc_read_extra_oob(struct mtd_info *mtd,
-					    u8 *oob, int *cur_off)
+					    u8 *oob, int *cur_off,
+					    bool randomize, int page)
 {
 	struct nand_chip *nand = mtd->priv;
 	struct nand_ecc_ctrl *ecc = &nand->ecc;
@@ -650,7 +853,11 @@ static void sunxi_nfc_hw_ecc_read_extra_oob(struct mtd_info *mtd,
 		nand->cmdfunc(mtd, NAND_CMD_RNDOUT,
 			      offset + mtd->writesize, -1);
 
-	sunxi_nfc_read_buf(mtd, oob + offset, len);
+	if (!randomize)
+		sunxi_nfc_read_buf(mtd, oob + offset, len);
+	else
+		sunxi_nfc_randomizer_read_buf(mtd, oob + offset, len,
+					      false, page);
 
 	*cur_off = mtd->oobsize + mtd->writesize;
 }
@@ -663,7 +870,8 @@ static inline u32 sunxi_nfc_buf_to_user_data(const u8 *buf)
 static int sunxi_nfc_hw_ecc_write_chunk(struct mtd_info *mtd,
 					const u8 *data, int data_off,
 					const u8 *oob, int oob_off,
-					int *cur_off)
+					int *cur_off, bool bbm,
+					int page)
 {
 	struct nand_chip *nand = mtd->priv;
 	struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);
@@ -673,11 +881,20 @@ static int sunxi_nfc_hw_ecc_write_chunk(struct mtd_info *mtd,
 	if (data_off != *cur_off)
 		nand->cmdfunc(mtd, NAND_CMD_RNDIN, data_off, -1);
 
-	sunxi_nfc_write_buf(mtd, data, ecc->size);
+	sunxi_nfc_randomizer_write_buf(mtd, data, ecc->size, false, page);
 
 	/* Fill OOB data in */
-	writel(sunxi_nfc_buf_to_user_data(oob),
-	       nfc->regs + NFC_REG_USER_DATA(0));
+	if ((nand->options & NAND_NEED_SCRAMBLING) && bbm) {
+		u8 user_data[4];
+
+		memcpy(user_data, oob, 4);
+		sunxi_nfc_randomize_bbm(mtd, page, user_data);
+		writel(sunxi_nfc_buf_to_user_data(user_data),
+		       nfc->regs + NFC_REG_USER_DATA(0));
+	} else {
+		writel(sunxi_nfc_buf_to_user_data(oob),
+		       nfc->regs + NFC_REG_USER_DATA(0));
+	}
 
 	if (data_off + ecc->size != oob_off)
 		nand->cmdfunc(mtd, NAND_CMD_RNDIN, oob_off, -1);
@@ -686,11 +903,13 @@ static int sunxi_nfc_hw_ecc_write_chunk(struct mtd_info *mtd,
 	if (ret)
 		return ret;
 
+	sunxi_nfc_randomizer_enable(mtd);
 	writel(NFC_DATA_TRANS | NFC_DATA_SWAP_METHOD |
 	       NFC_ACCESS_DIR | NFC_ECC_OP,
 	       nfc->regs + NFC_REG_CMD);
 
 	ret = sunxi_nfc_wait_int(nfc, NFC_CMD_INT_FLAG, 0);
+	sunxi_nfc_randomizer_disable(mtd);
 	if (ret)
 		return ret;
 
@@ -700,7 +919,8 @@ static int sunxi_nfc_hw_ecc_write_chunk(struct mtd_info *mtd,
 }
 
 static void sunxi_nfc_hw_ecc_write_extra_oob(struct mtd_info *mtd,
-					     u8 *oob, int *cur_off)
+					     u8 *oob, int *cur_off,
+					     int page)
 {
 	struct nand_chip *nand = mtd->priv;
 	struct nand_ecc_ctrl *ecc = &nand->ecc;
@@ -714,7 +934,7 @@ static void sunxi_nfc_hw_ecc_write_extra_oob(struct mtd_info *mtd,
 		nand->cmdfunc(mtd, NAND_CMD_RNDIN,
 			      offset + mtd->writesize, -1);
 
-	sunxi_nfc_write_buf(mtd, oob + offset, len);
+	sunxi_nfc_randomizer_write_buf(mtd, oob + offset, len, false, page);
 
 	*cur_off = mtd->oobsize + mtd->writesize;
 }
@@ -726,6 +946,7 @@ static int sunxi_nfc_hw_ecc_read_page(struct mtd_info *mtd,
 	struct nand_ecc_ctrl *ecc = &chip->ecc;
 	unsigned int max_bitflips = 0;
 	int ret, i, cur_off = 0;
+	bool raw_mode = false;
 
 	sunxi_nfc_hw_ecc_enable(mtd);
 
@@ -737,13 +958,17 @@ static int sunxi_nfc_hw_ecc_read_page(struct mtd_info *mtd,
 
 		ret = sunxi_nfc_hw_ecc_read_chunk(mtd, data, data_off, oob,
 						  oob_off + mtd->writesize,
-						  &cur_off, &max_bitflips);
-		if (ret)
+						  &cur_off, &max_bitflips,
+						  !i, page);
+		if (ret < 0)
 			return ret;
+		else if (ret)
+			raw_mode = true;
 	}
 
 	if (oob_required)
-		sunxi_nfc_hw_ecc_read_extra_oob(mtd, chip->oob_poi, &cur_off);
+		sunxi_nfc_hw_ecc_read_extra_oob(mtd, chip->oob_poi, &cur_off,
+						!raw_mode, page);
 
 	sunxi_nfc_hw_ecc_disable(mtd);
 
@@ -768,13 +993,14 @@ static int sunxi_nfc_hw_ecc_write_page(struct mtd_info *mtd,
 
 		ret = sunxi_nfc_hw_ecc_write_chunk(mtd, data, data_off, oob,
 						   oob_off + mtd->writesize,
-						   &cur_off);
+						   &cur_off, !i, page);
 		if (ret)
 			return ret;
 	}
 
-	if (oob_required)
-		sunxi_nfc_hw_ecc_write_extra_oob(mtd, chip->oob_poi, &cur_off);
+	if (oob_required || (chip->options & NAND_NEED_SCRAMBLING))
+		sunxi_nfc_hw_ecc_write_extra_oob(mtd, chip->oob_poi,
+						 &cur_off, page);
 
 	sunxi_nfc_hw_ecc_disable(mtd);
 
@@ -789,6 +1015,7 @@ static int sunxi_nfc_hw_syndrome_ecc_read_page(struct mtd_info *mtd,
 	struct nand_ecc_ctrl *ecc = &chip->ecc;
 	unsigned int max_bitflips = 0;
 	int ret, i, cur_off = 0;
+	bool raw_mode = false;
 
 	sunxi_nfc_hw_ecc_enable(mtd);
 
@@ -800,13 +1027,16 @@ static int sunxi_nfc_hw_syndrome_ecc_read_page(struct mtd_info *mtd,
 
 		ret = sunxi_nfc_hw_ecc_read_chunk(mtd, data, data_off, oob,
 						  oob_off, &cur_off,
-						  &max_bitflips);
-		if (ret)
+						  &max_bitflips, !i, page);
+		if (ret < 0)
 			return ret;
+		else if (ret)
+			raw_mode = true;
 	}
 
 	if (oob_required)
-		sunxi_nfc_hw_ecc_read_extra_oob(mtd, chip->oob_poi, &cur_off);
+		sunxi_nfc_hw_ecc_read_extra_oob(mtd, chip->oob_poi, &cur_off,
+						!raw_mode, page);
 
 	sunxi_nfc_hw_ecc_disable(mtd);
 
@@ -830,13 +1060,15 @@ static int sunxi_nfc_hw_syndrome_ecc_write_page(struct mtd_info *mtd,
 		const u8 *oob = chip->oob_poi + (i * (ecc->bytes + 4));
 
 		ret = sunxi_nfc_hw_ecc_write_chunk(mtd, data, data_off,
-						   oob, oob_off, &cur_off);
+						   oob, oob_off, &cur_off,
+						   false, page);
 		if (ret)
 			return ret;
 	}
 
-	if (oob_required)
-		sunxi_nfc_hw_ecc_write_extra_oob(mtd, chip->oob_poi, &cur_off);
+	if (oob_required || (chip->options & NAND_NEED_SCRAMBLING))
+		sunxi_nfc_hw_ecc_write_extra_oob(mtd, chip->oob_poi,
+						 &cur_off, page);
 
 	sunxi_nfc_hw_ecc_disable(mtd);
 
@@ -1347,6 +1579,9 @@ static int sunxi_nand_chip_init(struct device *dev, struct sunxi_nfc *nfc,
 	if (nand->bbt_options & NAND_BBT_USE_FLASH)
 		nand->bbt_options |= NAND_BBT_NO_OOB;
 
+	if (nand->options & NAND_NEED_SCRAMBLING)
+		nand->options |= NAND_NO_SUBPAGE_WRITE;
+
 	ret = sunxi_nand_chip_init_timings(chip, np);
 	if (ret) {
 		dev_err(dev, "could not configure chip timings: %d\n", ret);
-- 
2.1.4

[PATCH v2 3/3] mtd: nand: sunxi: add randomizer support

[Boris Brezillon]

Add support for the randomizer engine available in Allwinner's NFC IP.

Randomization is useful to support modern NAND chips which are sensitive to
repeated patterns. On such NANDs you might experience an unexpectedly high
number of bitflips when you repeat the same pattern all over a given NAND
block.
Randomizing input data mitigate this problem by avoiding such repeated
patterns.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
---
 drivers/mtd/nand/sunxi_nand.c | 287 ++++++++++++++++++++++++++++++++++++++----
 1 file changed, 261 insertions(+), 26 deletions(-)

diff --git a/drivers/mtd/nand/sunxi_nand.c b/drivers/mtd/nand/sunxi_nand.c
index 1bbcc0c..43f25327f 100644
--- a/drivers/mtd/nand/sunxi_nand.c
+++ b/drivers/mtd/nand/sunxi_nand.c
@@ -60,6 +60,7 @@
 #define NFC_REG_ECC_ERR_CNT(x)	((0x0040 + (x)) & ~0x3)
 #define NFC_REG_USER_DATA(x)	(0x0050 + ((x) * 4))
 #define NFC_REG_SPARE_AREA	0x00A0
+#define NFC_REG_PAT_ID		0x00A4
 #define NFC_RAM0_BASE		0x0400
 #define NFC_RAM1_BASE		0x0800
 
@@ -539,6 +540,174 @@ static void sunxi_nfc_cmd_ctrl(struct mtd_info *mtd, int dat,
 	sunxi_nfc_wait_int(nfc, NFC_CMD_INT_FLAG, 0);
 }
 
+/* These seed values have been extracted from Allwinner's BSP */
+static const u16 sunxi_nfc_randomizer_page_seeds[] = {
+	0x2b75, 0x0bd0, 0x5ca3, 0x62d1, 0x1c93, 0x07e9, 0x2162, 0x3a72,
+	0x0d67, 0x67f9, 0x1be7, 0x077d, 0x032f, 0x0dac, 0x2716, 0x2436,
+	0x7922, 0x1510, 0x3860, 0x5287, 0x480f, 0x4252, 0x1789, 0x5a2d,
+	0x2a49, 0x5e10, 0x437f, 0x4b4e, 0x2f45, 0x216e, 0x5cb7, 0x7130,
+	0x2a3f, 0x60e4, 0x4dc9, 0x0ef0, 0x0f52, 0x1bb9, 0x6211, 0x7a56,
+	0x226d, 0x4ea7, 0x6f36, 0x3692, 0x38bf, 0x0c62, 0x05eb, 0x4c55,
+	0x60f4, 0x728c, 0x3b6f, 0x2037, 0x7f69, 0x0936, 0x651a, 0x4ceb,
+	0x6218, 0x79f3, 0x383f, 0x18d9, 0x4f05, 0x5c82, 0x2912, 0x6f17,
+	0x6856, 0x5938, 0x1007, 0x61ab, 0x3e7f, 0x57c2, 0x542f, 0x4f62,
+	0x7454, 0x2eac, 0x7739, 0x42d4, 0x2f90, 0x435a, 0x2e52, 0x2064,
+	0x637c, 0x66ad, 0x2c90, 0x0bad, 0x759c, 0x0029, 0x0986, 0x7126,
+	0x1ca7, 0x1605, 0x386a, 0x27f5, 0x1380, 0x6d75, 0x24c3, 0x0f8e,
+	0x2b7a, 0x1418, 0x1fd1, 0x7dc1, 0x2d8e, 0x43af, 0x2267, 0x7da3,
+	0x4e3d, 0x1338, 0x50db, 0x454d, 0x764d, 0x40a3, 0x42e6, 0x262b,
+	0x2d2e, 0x1aea, 0x2e17, 0x173d, 0x3a6e, 0x71bf, 0x25f9, 0x0a5d,
+	0x7c57, 0x0fbe, 0x46ce, 0x4939, 0x6b17, 0x37bb, 0x3e91, 0x76db,
+};
+
+/*
+ * sunxi_nfc_randomizer_ecc512_seeds and sunxi_nfc_randomizer_ecc1024_seeds
+ * have been generated using
+ * sunxi_nfc_randomizer_step(seed, (step_size * 8) + 15), which is what
+ * the randomizer engine does internally before de/scrambling OOB data.
+ *
+ * Those tables are statically defined to avoid calculating randomizer state
+ * at runtime.
+ */
+static const u16 sunxi_nfc_randomizer_ecc512_seeds[] = {
+	0x3346, 0x367f, 0x1f18, 0x769a, 0x4f64, 0x068c, 0x2ef1, 0x6b64,
+	0x28a9, 0x15d7, 0x30f8, 0x3659, 0x53db, 0x7c5f, 0x71d4, 0x4409,
+	0x26eb, 0x03cc, 0x655d, 0x47d4, 0x4daa, 0x0877, 0x712d, 0x3617,
+	0x3264, 0x49aa, 0x7f9e, 0x588e, 0x4fbc, 0x7176, 0x7f91, 0x6c6d,
+	0x4b95, 0x5fb7, 0x3844, 0x4037, 0x0184, 0x081b, 0x0ee8, 0x5b91,
+	0x293d, 0x1f71, 0x0e6f, 0x402b, 0x5122, 0x1e52, 0x22be, 0x3d2d,
+	0x75bc, 0x7c60, 0x6291, 0x1a2f, 0x61d4, 0x74aa, 0x4140, 0x29ab,
+	0x472d, 0x2852, 0x017e, 0x15e8, 0x5ec2, 0x17cf, 0x7d0f, 0x06b8,
+	0x117a, 0x6b94, 0x789b, 0x3126, 0x6ac5, 0x5be7, 0x150f, 0x51f8,
+	0x7889, 0x0aa5, 0x663d, 0x77e8, 0x0b87, 0x3dcb, 0x360d, 0x218b,
+	0x512f, 0x7dc9, 0x6a4d, 0x630a, 0x3547, 0x1dd2, 0x5aea, 0x69a5,
+	0x7bfa, 0x5e4f, 0x1519, 0x6430, 0x3a0e, 0x5eb3, 0x5425, 0x0c7a,
+	0x5540, 0x3670, 0x63c1, 0x31e9, 0x5a39, 0x2de7, 0x5979, 0x2891,
+	0x1562, 0x014b, 0x5b05, 0x2756, 0x5a34, 0x13aa, 0x6cb5, 0x2c36,
+	0x5e72, 0x1306, 0x0861, 0x15ef, 0x1ee8, 0x5a37, 0x7ac4, 0x45dd,
+	0x44c4, 0x7266, 0x2f41, 0x3ccc, 0x045e, 0x7d40, 0x7c66, 0x0fa0,
+};
+
+static const u16 sunxi_nfc_randomizer_ecc1024_seeds[] = {
+	0x2cf5, 0x35f1, 0x63a4, 0x5274, 0x2bd2, 0x778b, 0x7285, 0x32b6,
+	0x6a5c, 0x70d6, 0x757d, 0x6769, 0x5375, 0x1e81, 0x0cf3, 0x3982,
+	0x6787, 0x042a, 0x6c49, 0x1925, 0x56a8, 0x40a9, 0x063e, 0x7bd9,
+	0x4dbf, 0x55ec, 0x672e, 0x7334, 0x5185, 0x4d00, 0x232a, 0x7e07,
+	0x445d, 0x6b92, 0x528f, 0x4255, 0x53ba, 0x7d82, 0x2a2e, 0x3a4e,
+	0x75eb, 0x450c, 0x6844, 0x1b5d, 0x581a, 0x4cc6, 0x0379, 0x37b2,
+	0x419f, 0x0e92, 0x6b27, 0x5624, 0x01e3, 0x07c1, 0x44a5, 0x130c,
+	0x13e8, 0x5910, 0x0876, 0x60c5, 0x54e3, 0x5b7f, 0x2269, 0x509f,
+	0x7665, 0x36fd, 0x3e9a, 0x0579, 0x6295, 0x14ef, 0x0a81, 0x1bcc,
+	0x4b16, 0x64db, 0x0514, 0x4f07, 0x0591, 0x3576, 0x6853, 0x0d9e,
+	0x259f, 0x38b7, 0x64fb, 0x3094, 0x4693, 0x6ddd, 0x29bb, 0x0bc8,
+	0x3f47, 0x490e, 0x0c0e, 0x7933, 0x3c9e, 0x5840, 0x398d, 0x3e68,
+	0x4af1, 0x71f5, 0x57cf, 0x1121, 0x64eb, 0x3579, 0x15ac, 0x584d,
+	0x5f2a, 0x47e2, 0x6528, 0x6eac, 0x196e, 0x6b96, 0x0450, 0x0179,
+	0x609c, 0x06e1, 0x4626, 0x42c7, 0x273e, 0x486f, 0x0705, 0x1601,
+	0x145b, 0x407e, 0x062b, 0x57a5, 0x53f9, 0x5659, 0x4410, 0x3ccd,
+};
+
+static u16 sunxi_nfc_randomizer_step(u16 state, int count)
+{
+	state &= 0x7fff;
+
+	/*
+	 * This loop is just a simple implementation of a Fibonacci LFSR using
+	 * the x16 + x15 + 1 polynomial.
+	 */
+	while (count--)
+		state = ((state >> 1) |
+			 (((state ^ (state >> 1)) & 1) << 14)) & 0x7fff;
+
+	return state;
+}
+
+static u16 sunxi_nfc_randomizer_state(struct mtd_info *mtd, int page, bool ecc)
+{
+	const u16 *seeds = sunxi_nfc_randomizer_page_seeds;
+	int mod = mtd->erasesize / mtd->writesize;
+
+	if (mod > ARRAY_SIZE(sunxi_nfc_randomizer_page_seeds))
+		mod = ARRAY_SIZE(sunxi_nfc_randomizer_page_seeds);
+
+	if (ecc) {
+		if (mtd->ecc_step_size == 512)
+			seeds = sunxi_nfc_randomizer_ecc512_seeds;
+		else
+			seeds = sunxi_nfc_randomizer_ecc1024_seeds;
+	}
+
+	return seeds[page % mod];
+}
+
+static void sunxi_nfc_randomizer_config(struct mtd_info *mtd,
+					int page, bool ecc)
+{
+	struct nand_chip *nand = mtd->priv;
+	struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);
+	u32 ecc_ctl = readl(nfc->regs + NFC_REG_ECC_CTL);
+	u16 state;
+
+	if (!(nand->options & NAND_NEED_SCRAMBLING))
+		return;
+
+	ecc_ctl = readl(nfc->regs + NFC_REG_ECC_CTL);
+	state = sunxi_nfc_randomizer_state(mtd, page, ecc);
+	ecc_ctl = readl(nfc->regs + NFC_REG_ECC_CTL) & ~NFC_RANDOM_SEED_MSK;
+	writel(ecc_ctl | NFC_RANDOM_SEED(state), nfc->regs + NFC_REG_ECC_CTL);
+}
+
+static void sunxi_nfc_randomizer_enable(struct mtd_info *mtd)
+{
+	struct nand_chip *nand = mtd->priv;
+	struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);
+
+	if (!(nand->options & NAND_NEED_SCRAMBLING))
+		return;
+
+	writel(readl(nfc->regs + NFC_REG_ECC_CTL) | NFC_RANDOM_EN,
+	       nfc->regs + NFC_REG_ECC_CTL);
+}
+
+static void sunxi_nfc_randomizer_disable(struct mtd_info *mtd)
+{
+	struct nand_chip *nand = mtd->priv;
+	struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);
+
+	if (!(nand->options & NAND_NEED_SCRAMBLING))
+		return;
+
+	writel(readl(nfc->regs + NFC_REG_ECC_CTL) & ~NFC_RANDOM_EN,
+	       nfc->regs + NFC_REG_ECC_CTL);
+}
+
+static void sunxi_nfc_randomize_bbm(struct mtd_info *mtd, int page, u8 *bbm)
+{
+	u16 state = sunxi_nfc_randomizer_state(mtd, page, true);
+
+	bbm[0] ^= state;
+	bbm[1] ^= sunxi_nfc_randomizer_step(state, 8);
+}
+
+static void sunxi_nfc_randomizer_write_buf(struct mtd_info *mtd,
+					   const uint8_t *buf, int len,
+					   bool ecc, int page)
+{
+	sunxi_nfc_randomizer_config(mtd, page, ecc);
+	sunxi_nfc_randomizer_enable(mtd);
+	sunxi_nfc_write_buf(mtd, buf, len);
+	sunxi_nfc_randomizer_disable(mtd);
+}
+
+static void sunxi_nfc_randomizer_read_buf(struct mtd_info *mtd, uint8_t *buf,
+					  int len, bool ecc, int page)
+{
+	sunxi_nfc_randomizer_config(mtd, page, ecc);
+	sunxi_nfc_randomizer_enable(mtd);
+	sunxi_nfc_read_buf(mtd, buf, len);
+	sunxi_nfc_randomizer_disable(mtd);
+}
+
 static void sunxi_nfc_hw_ecc_enable(struct mtd_info *mtd)
 {
 	struct nand_chip *nand = mtd->priv;
@@ -575,18 +744,20 @@ static int sunxi_nfc_hw_ecc_read_chunk(struct mtd_info *mtd,
 				       u8 *data, int data_off,
 				       u8 *oob, int oob_off,
 				       int *cur_off,
-				       unsigned int *max_bitflips)
+				       unsigned int *max_bitflips,
+				       bool bbm, int page)
 {
 	struct nand_chip *nand = mtd->priv;
 	struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);
 	struct nand_ecc_ctrl *ecc = &nand->ecc;
+	int raw_mode = 0;
 	u32 status;
 	int ret;
 
 	if (*cur_off != data_off)
 		nand->cmdfunc(mtd, NAND_CMD_RNDOUT, data_off, -1);
 
-	sunxi_nfc_read_buf(mtd, NULL, ecc->size);
+	sunxi_nfc_randomizer_read_buf(mtd, NULL, ecc->size, false, page);
 
 	if (data_off + ecc->size != oob_off)
 		nand->cmdfunc(mtd, NAND_CMD_RNDOUT, oob_off, -1);
@@ -595,25 +766,54 @@ static int sunxi_nfc_hw_ecc_read_chunk(struct mtd_info *mtd,
 	if (ret)
 		return ret;
 
+	sunxi_nfc_randomizer_enable(mtd);
 	writel(NFC_DATA_TRANS | NFC_DATA_SWAP_METHOD | NFC_ECC_OP,
 	       nfc->regs + NFC_REG_CMD);
 
 	ret = sunxi_nfc_wait_int(nfc, NFC_CMD_INT_FLAG, 0);
+	sunxi_nfc_randomizer_disable(mtd);
 	if (ret)
 		return ret;
 
+	*cur_off = oob_off + ecc->bytes + 4;
+
 	status = readl(nfc->regs + NFC_REG_ECC_ST);
+	if (status & NFC_ECC_PAT_FOUND(0)) {
+		u8 pattern = 0xff;
+
+		if (unlikely(!(readl(nfc->regs + NFC_REG_PAT_ID) & 0x1)))
+			pattern = 0x0;
+
+		memset(data, pattern, ecc->size);
+		memset(oob, pattern, ecc->bytes + 4);
+
+		return 1;
+	}
+
 	ret = NFC_ECC_ERR_CNT(0, readl(nfc->regs + NFC_REG_ECC_ERR_CNT(0)));
 
 	memcpy_fromio(data, nfc->regs + NFC_RAM0_BASE, ecc->size);
 
 	nand->cmdfunc(mtd, NAND_CMD_RNDOUT, oob_off, -1);
-	sunxi_nfc_read_buf(mtd, oob, ecc->bytes + 4);
+	sunxi_nfc_randomizer_read_buf(mtd, oob, ecc->bytes + 4, true, page);
 
 	if (status & NFC_ECC_ERR(0)) {
+		/*
+		 * Re-read the data with the randomizer disabled to identify
+		 * bitflips in erased pages.
+		 */
+		if (nand->options & NAND_NEED_SCRAMBLING) {
+			nand->cmdfunc(mtd, NAND_CMD_RNDOUT, data_off, -1);
+			nand->read_buf(mtd, data, ecc->size);
+			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 {
 		/*
 		 * The engine protects 4 bytes of OOB data per chunk.
@@ -621,6 +821,10 @@ static int sunxi_nfc_hw_ecc_read_chunk(struct mtd_info *mtd,
 		 */
 		sunxi_nfc_user_data_to_buf(readl(nfc->regs + NFC_REG_USER_DATA(0)),
 					   oob);
+
+		/* De-randomize the Bad Block Marker. */
+		if (bbm && nand->options & NAND_NEED_SCRAMBLING)
+			sunxi_nfc_randomize_bbm(mtd, page, oob);
 	}
 
 	if (ret < 0) {
@@ -630,13 +834,12 @@ static int sunxi_nfc_hw_ecc_read_chunk(struct mtd_info *mtd,
 		*max_bitflips = max_t(unsigned int, *max_bitflips, ret);
 	}
 
-	*cur_off = oob_off + ecc->bytes + 4;
-
-	return 0;
+	return raw_mode;
 }
 
 static void sunxi_nfc_hw_ecc_read_extra_oob(struct mtd_info *mtd,
-					    u8 *oob, int *cur_off)
+					    u8 *oob, int *cur_off,
+					    bool randomize, int page)
 {
 	struct nand_chip *nand = mtd->priv;
 	struct nand_ecc_ctrl *ecc = &nand->ecc;
@@ -650,7 +853,11 @@ static void sunxi_nfc_hw_ecc_read_extra_oob(struct mtd_info *mtd,
 		nand->cmdfunc(mtd, NAND_CMD_RNDOUT,
 			      offset + mtd->writesize, -1);
 
-	sunxi_nfc_read_buf(mtd, oob + offset, len);
+	if (!randomize)
+		sunxi_nfc_read_buf(mtd, oob + offset, len);
+	else
+		sunxi_nfc_randomizer_read_buf(mtd, oob + offset, len,
+					      false, page);
 
 	*cur_off = mtd->oobsize + mtd->writesize;
 }
@@ -663,7 +870,8 @@ static inline u32 sunxi_nfc_buf_to_user_data(const u8 *buf)
 static int sunxi_nfc_hw_ecc_write_chunk(struct mtd_info *mtd,
 					const u8 *data, int data_off,
 					const u8 *oob, int oob_off,
-					int *cur_off)
+					int *cur_off, bool bbm,
+					int page)
 {
 	struct nand_chip *nand = mtd->priv;
 	struct sunxi_nfc *nfc = to_sunxi_nfc(nand->controller);
@@ -673,11 +881,20 @@ static int sunxi_nfc_hw_ecc_write_chunk(struct mtd_info *mtd,
 	if (data_off != *cur_off)
 		nand->cmdfunc(mtd, NAND_CMD_RNDIN, data_off, -1);
 
-	sunxi_nfc_write_buf(mtd, data, ecc->size);
+	sunxi_nfc_randomizer_write_buf(mtd, data, ecc->size, false, page);
 
 	/* Fill OOB data in */
-	writel(sunxi_nfc_buf_to_user_data(oob),
-	       nfc->regs + NFC_REG_USER_DATA(0));
+	if ((nand->options & NAND_NEED_SCRAMBLING) && bbm) {
+		u8 user_data[4];
+
+		memcpy(user_data, oob, 4);
+		sunxi_nfc_randomize_bbm(mtd, page, user_data);
+		writel(sunxi_nfc_buf_to_user_data(user_data),
+		       nfc->regs + NFC_REG_USER_DATA(0));
+	} else {
+		writel(sunxi_nfc_buf_to_user_data(oob),
+		       nfc->regs + NFC_REG_USER_DATA(0));
+	}
 
 	if (data_off + ecc->size != oob_off)
 		nand->cmdfunc(mtd, NAND_CMD_RNDIN, oob_off, -1);
@@ -686,11 +903,13 @@ static int sunxi_nfc_hw_ecc_write_chunk(struct mtd_info *mtd,
 	if (ret)
 		return ret;
 
+	sunxi_nfc_randomizer_enable(mtd);
 	writel(NFC_DATA_TRANS | NFC_DATA_SWAP_METHOD |
 	       NFC_ACCESS_DIR | NFC_ECC_OP,
 	       nfc->regs + NFC_REG_CMD);
 
 	ret = sunxi_nfc_wait_int(nfc, NFC_CMD_INT_FLAG, 0);
+	sunxi_nfc_randomizer_disable(mtd);
 	if (ret)
 		return ret;
 
@@ -700,7 +919,8 @@ static int sunxi_nfc_hw_ecc_write_chunk(struct mtd_info *mtd,
 }
 
 static void sunxi_nfc_hw_ecc_write_extra_oob(struct mtd_info *mtd,
-					     u8 *oob, int *cur_off)
+					     u8 *oob, int *cur_off,
+					     int page)
 {
 	struct nand_chip *nand = mtd->priv;
 	struct nand_ecc_ctrl *ecc = &nand->ecc;
@@ -714,7 +934,7 @@ static void sunxi_nfc_hw_ecc_write_extra_oob(struct mtd_info *mtd,
 		nand->cmdfunc(mtd, NAND_CMD_RNDIN,
 			      offset + mtd->writesize, -1);
 
-	sunxi_nfc_write_buf(mtd, oob + offset, len);
+	sunxi_nfc_randomizer_write_buf(mtd, oob + offset, len, false, page);
 
 	*cur_off = mtd->oobsize + mtd->writesize;
 }
@@ -726,6 +946,7 @@ static int sunxi_nfc_hw_ecc_read_page(struct mtd_info *mtd,
 	struct nand_ecc_ctrl *ecc = &chip->ecc;
 	unsigned int max_bitflips = 0;
 	int ret, i, cur_off = 0;
+	bool raw_mode = false;
 
 	sunxi_nfc_hw_ecc_enable(mtd);
 
@@ -737,13 +958,17 @@ static int sunxi_nfc_hw_ecc_read_page(struct mtd_info *mtd,
 
 		ret = sunxi_nfc_hw_ecc_read_chunk(mtd, data, data_off, oob,
 						  oob_off + mtd->writesize,
-						  &cur_off, &max_bitflips);
-		if (ret)
+						  &cur_off, &max_bitflips,
+						  !i, page);
+		if (ret < 0)
 			return ret;
+		else if (ret)
+			raw_mode = true;
 	}
 
 	if (oob_required)
-		sunxi_nfc_hw_ecc_read_extra_oob(mtd, chip->oob_poi, &cur_off);
+		sunxi_nfc_hw_ecc_read_extra_oob(mtd, chip->oob_poi, &cur_off,
+						!raw_mode, page);
 
 	sunxi_nfc_hw_ecc_disable(mtd);
 
@@ -768,13 +993,14 @@ static int sunxi_nfc_hw_ecc_write_page(struct mtd_info *mtd,
 
 		ret = sunxi_nfc_hw_ecc_write_chunk(mtd, data, data_off, oob,
 						   oob_off + mtd->writesize,
-						   &cur_off);
+						   &cur_off, !i, page);
 		if (ret)
 			return ret;
 	}
 
-	if (oob_required)
-		sunxi_nfc_hw_ecc_write_extra_oob(mtd, chip->oob_poi, &cur_off);
+	if (oob_required || (chip->options & NAND_NEED_SCRAMBLING))
+		sunxi_nfc_hw_ecc_write_extra_oob(mtd, chip->oob_poi,
+						 &cur_off, page);
 
 	sunxi_nfc_hw_ecc_disable(mtd);
 
@@ -789,6 +1015,7 @@ static int sunxi_nfc_hw_syndrome_ecc_read_page(struct mtd_info *mtd,
 	struct nand_ecc_ctrl *ecc = &chip->ecc;
 	unsigned int max_bitflips = 0;
 	int ret, i, cur_off = 0;
+	bool raw_mode = false;
 
 	sunxi_nfc_hw_ecc_enable(mtd);
 
@@ -800,13 +1027,16 @@ static int sunxi_nfc_hw_syndrome_ecc_read_page(struct mtd_info *mtd,
 
 		ret = sunxi_nfc_hw_ecc_read_chunk(mtd, data, data_off, oob,
 						  oob_off, &cur_off,
-						  &max_bitflips);
-		if (ret)
+						  &max_bitflips, !i, page);
+		if (ret < 0)
 			return ret;
+		else if (ret)
+			raw_mode = true;
 	}
 
 	if (oob_required)
-		sunxi_nfc_hw_ecc_read_extra_oob(mtd, chip->oob_poi, &cur_off);
+		sunxi_nfc_hw_ecc_read_extra_oob(mtd, chip->oob_poi, &cur_off,
+						!raw_mode, page);
 
 	sunxi_nfc_hw_ecc_disable(mtd);
 
@@ -830,13 +1060,15 @@ static int sunxi_nfc_hw_syndrome_ecc_write_page(struct mtd_info *mtd,
 		const u8 *oob = chip->oob_poi + (i * (ecc->bytes + 4));
 
 		ret = sunxi_nfc_hw_ecc_write_chunk(mtd, data, data_off,
-						   oob, oob_off, &cur_off);
+						   oob, oob_off, &cur_off,
+						   false, page);
 		if (ret)
 			return ret;
 	}
 
-	if (oob_required)
-		sunxi_nfc_hw_ecc_write_extra_oob(mtd, chip->oob_poi, &cur_off);
+	if (oob_required || (chip->options & NAND_NEED_SCRAMBLING))
+		sunxi_nfc_hw_ecc_write_extra_oob(mtd, chip->oob_poi,
+						 &cur_off, page);
 
 	sunxi_nfc_hw_ecc_disable(mtd);
 
@@ -1347,6 +1579,9 @@ static int sunxi_nand_chip_init(struct device *dev, struct sunxi_nfc *nfc,
 	if (nand->bbt_options & NAND_BBT_USE_FLASH)
 		nand->bbt_options |= NAND_BBT_NO_OOB;
 
+	if (nand->options & NAND_NEED_SCRAMBLING)
+		nand->options |= NAND_NO_SUBPAGE_WRITE;
+
 	ret = sunxi_nand_chip_init_timings(chip, np);
 	if (ret) {
 		dev_err(dev, "could not configure chip timings: %d\n", ret);
-- 
2.1.4

Re: [PATCH v2 3/3] mtd: nand: sunxi: add randomizer support

[Brian Norris]

All three look good, so pushed to l2-mtd.git/next. One comment below:

On Wed, Dec 02, 2015 at 12:01:07PM +0100, Boris Brezillon wrote:

...

> +static u16 sunxi_nfc_randomizer_state(struct mtd_info *mtd, int page, bool ecc)
> +{
> +	const u16 *seeds = sunxi_nfc_randomizer_page_seeds;
> +	int mod = mtd->erasesize / mtd->writesize;

Richard suggested you use the mtd.h helper here. Patch below.

> +
> +	if (mod > ARRAY_SIZE(sunxi_nfc_randomizer_page_seeds))
> +		mod = ARRAY_SIZE(sunxi_nfc_randomizer_page_seeds);
> +
> +	if (ecc) {
> +		if (mtd->ecc_step_size == 512)
> +			seeds = sunxi_nfc_randomizer_ecc512_seeds;
> +		else
> +			seeds = sunxi_nfc_randomizer_ecc1024_seeds;
> +	}
> +
> +	return seeds[page % mod];
> +}

From: Brian Norris <computersforpeace@gmail.com>
Date: Fri, 22 Jan 2016 18:54:02 -0800
Subject: [PATCH] mtd: nand: sunxi: use mtd_div_by_ws() helper

Suggested-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
---
 drivers/mtd/nand/sunxi_nand.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/sunxi_nand.c b/drivers/mtd/nand/sunxi_nand.c
index 5f700719d5c2..b5ea6b312df0 100644
--- a/drivers/mtd/nand/sunxi_nand.c
+++ b/drivers/mtd/nand/sunxi_nand.c
@@ -624,7 +624,7 @@ static u16 sunxi_nfc_randomizer_step(u16 state, int count)
 static u16 sunxi_nfc_randomizer_state(struct mtd_info *mtd, int page, bool ecc)
 {
 	const u16 *seeds = sunxi_nfc_randomizer_page_seeds;
-	int mod = mtd->erasesize / mtd->writesize;
+	int mod = mtd_div_by_ws(mtd->erasesize, mtd);
 
 	if (mod > ARRAY_SIZE(sunxi_nfc_randomizer_page_seeds))
 		mod = ARRAY_SIZE(sunxi_nfc_randomizer_page_seeds);
-- 
2.7.0.rc3.207.g0ac5344

[PATCH v2 3/3] mtd: nand: sunxi: add randomizer support

[Brian Norris]

All three look good, so pushed to l2-mtd.git/next. One comment below:

On Wed, Dec 02, 2015 at 12:01:07PM +0100, Boris Brezillon wrote:

...

> +static u16 sunxi_nfc_randomizer_state(struct mtd_info *mtd, int page, bool ecc)
> +{
> +	const u16 *seeds = sunxi_nfc_randomizer_page_seeds;
> +	int mod = mtd->erasesize / mtd->writesize;

Richard suggested you use the mtd.h helper here. Patch below.

> +
> +	if (mod > ARRAY_SIZE(sunxi_nfc_randomizer_page_seeds))
> +		mod = ARRAY_SIZE(sunxi_nfc_randomizer_page_seeds);
> +
> +	if (ecc) {
> +		if (mtd->ecc_step_size == 512)
> +			seeds = sunxi_nfc_randomizer_ecc512_seeds;
> +		else
> +			seeds = sunxi_nfc_randomizer_ecc1024_seeds;
> +	}
> +
> +	return seeds[page % mod];
> +}

From: Brian Norris <computersforpeace@gmail.com>
Date: Fri, 22 Jan 2016 18:54:02 -0800
Subject: [PATCH] mtd: nand: sunxi: use mtd_div_by_ws() helper

Suggested-by: Richard Weinberger <richard@nod.at>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>
---
 drivers/mtd/nand/sunxi_nand.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/sunxi_nand.c b/drivers/mtd/nand/sunxi_nand.c
index 5f700719d5c2..b5ea6b312df0 100644
--- a/drivers/mtd/nand/sunxi_nand.c
+++ b/drivers/mtd/nand/sunxi_nand.c
@@ -624,7 +624,7 @@ static u16 sunxi_nfc_randomizer_step(u16 state, int count)
 static u16 sunxi_nfc_randomizer_state(struct mtd_info *mtd, int page, bool ecc)
 {
 	const u16 *seeds = sunxi_nfc_randomizer_page_seeds;
-	int mod = mtd->erasesize / mtd->writesize;
+	int mod = mtd_div_by_ws(mtd->erasesize, mtd);
 
 	if (mod > ARRAY_SIZE(sunxi_nfc_randomizer_page_seeds))
 		mod = ARRAY_SIZE(sunxi_nfc_randomizer_page_seeds);
-- 
2.7.0.rc3.207.g0ac5344

Re: [PATCH v2 3/3] mtd: nand: sunxi: add randomizer support

[Boris Brezillon]

Hi Brian,

On Fri, 22 Jan 2016 18:57:13 -0800
Brian Norris <computersforpeace@gmail.com> wrote:

> All three look good, so pushed to l2-mtd.git/next. One comment below:

Thanks.

> 
> On Wed, Dec 02, 2015 at 12:01:07PM +0100, Boris Brezillon wrote:
> 
> ...
> 
> > +static u16 sunxi_nfc_randomizer_state(struct mtd_info *mtd, int page, bool ecc)
> > +{
> > +	const u16 *seeds = sunxi_nfc_randomizer_page_seeds;
> > +	int mod = mtd->erasesize / mtd->writesize;
> 
> Richard suggested you use the mtd.h helper here. Patch below.

Yep, I forgot to do this change.

> 
> > +
> > +	if (mod > ARRAY_SIZE(sunxi_nfc_randomizer_page_seeds))
> > +		mod = ARRAY_SIZE(sunxi_nfc_randomizer_page_seeds);
> > +
> > +	if (ecc) {
> > +		if (mtd->ecc_step_size == 512)
> > +			seeds = sunxi_nfc_randomizer_ecc512_seeds;
> > +		else
> > +			seeds = sunxi_nfc_randomizer_ecc1024_seeds;
> > +	}
> > +
> > +	return seeds[page % mod];
> > +}
> 
> From: Brian Norris <computersforpeace@gmail.com>
> Date: Fri, 22 Jan 2016 18:54:02 -0800
> Subject: [PATCH] mtd: nand: sunxi: use mtd_div_by_ws() helper
> 
> Suggested-by: Richard Weinberger <richard@nod.at>
> Signed-off-by: Brian Norris <computersforpeace@gmail.com>

Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>

> ---
>  drivers/mtd/nand/sunxi_nand.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/nand/sunxi_nand.c b/drivers/mtd/nand/sunxi_nand.c
> index 5f700719d5c2..b5ea6b312df0 100644
> --- a/drivers/mtd/nand/sunxi_nand.c
> +++ b/drivers/mtd/nand/sunxi_nand.c
> @@ -624,7 +624,7 @@ static u16 sunxi_nfc_randomizer_step(u16 state, int count)
>  static u16 sunxi_nfc_randomizer_state(struct mtd_info *mtd, int page, bool ecc)
>  {
>  	const u16 *seeds = sunxi_nfc_randomizer_page_seeds;
> -	int mod = mtd->erasesize / mtd->writesize;
> +	int mod = mtd_div_by_ws(mtd->erasesize, mtd);

Just a comment (which should not prevent you from applying this patch).
Isn't it a bit overkill to cast the erasesize to a 64 bit value, and
then do a do_div on it. Shouldn't happen often though, because
->writesize_shift should be != 0 in most (all?) cases.

Another related remark: with the MLC/paired pages stuff I'll have to
retrieve this information (number of write units per erase block) quite
often, so maybe we should have a field (and/or an helper) for that.

Thanks,

Boris


-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

[PATCH v2 3/3] mtd: nand: sunxi: add randomizer support

[Boris Brezillon]

Hi Brian,

On Fri, 22 Jan 2016 18:57:13 -0800
Brian Norris <computersforpeace@gmail.com> wrote:

> All three look good, so pushed to l2-mtd.git/next. One comment below:

Thanks.

> 
> On Wed, Dec 02, 2015 at 12:01:07PM +0100, Boris Brezillon wrote:
> 
> ...
> 
> > +static u16 sunxi_nfc_randomizer_state(struct mtd_info *mtd, int page, bool ecc)
> > +{
> > +	const u16 *seeds = sunxi_nfc_randomizer_page_seeds;
> > +	int mod = mtd->erasesize / mtd->writesize;
> 
> Richard suggested you use the mtd.h helper here. Patch below.

Yep, I forgot to do this change.

> 
> > +
> > +	if (mod > ARRAY_SIZE(sunxi_nfc_randomizer_page_seeds))
> > +		mod = ARRAY_SIZE(sunxi_nfc_randomizer_page_seeds);
> > +
> > +	if (ecc) {
> > +		if (mtd->ecc_step_size == 512)
> > +			seeds = sunxi_nfc_randomizer_ecc512_seeds;
> > +		else
> > +			seeds = sunxi_nfc_randomizer_ecc1024_seeds;
> > +	}
> > +
> > +	return seeds[page % mod];
> > +}
> 
> From: Brian Norris <computersforpeace@gmail.com>
> Date: Fri, 22 Jan 2016 18:54:02 -0800
> Subject: [PATCH] mtd: nand: sunxi: use mtd_div_by_ws() helper
> 
> Suggested-by: Richard Weinberger <richard@nod.at>
> Signed-off-by: Brian Norris <computersforpeace@gmail.com>

Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>

> ---
>  drivers/mtd/nand/sunxi_nand.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/nand/sunxi_nand.c b/drivers/mtd/nand/sunxi_nand.c
> index 5f700719d5c2..b5ea6b312df0 100644
> --- a/drivers/mtd/nand/sunxi_nand.c
> +++ b/drivers/mtd/nand/sunxi_nand.c
> @@ -624,7 +624,7 @@ static u16 sunxi_nfc_randomizer_step(u16 state, int count)
>  static u16 sunxi_nfc_randomizer_state(struct mtd_info *mtd, int page, bool ecc)
>  {
>  	const u16 *seeds = sunxi_nfc_randomizer_page_seeds;
> -	int mod = mtd->erasesize / mtd->writesize;
> +	int mod = mtd_div_by_ws(mtd->erasesize, mtd);

Just a comment (which should not prevent you from applying this patch).
Isn't it a bit overkill to cast the erasesize to a 64 bit value, and
then do a do_div on it. Shouldn't happen often though, because
->writesize_shift should be != 0 in most (all?) cases.

Another related remark: with the MLC/paired pages stuff I'll have to
retrieve this information (number of write units per erase block) quite
often, so maybe we should have a field (and/or an helper) for that.

Thanks,

Boris


-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

Re: [PATCH v2 3/3] mtd: nand: sunxi: add randomizer support

[Brian Norris]

On Sat, Jan 23, 2016 at 09:18:44AM +0100, Boris Brezillon wrote:
> On Fri, 22 Jan 2016 18:57:13 -0800
> Brian Norris <computersforpeace@gmail.com> wrote:
> > 
> > From: Brian Norris <computersforpeace@gmail.com>
> > Date: Fri, 22 Jan 2016 18:54:02 -0800
> > Subject: [PATCH] mtd: nand: sunxi: use mtd_div_by_ws() helper
> > 
> > Suggested-by: Richard Weinberger <richard@nod.at>
> > Signed-off-by: Brian Norris <computersforpeace@gmail.com>
> 
> Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>

Applied.

> > ---
> >  drivers/mtd/nand/sunxi_nand.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/mtd/nand/sunxi_nand.c b/drivers/mtd/nand/sunxi_nand.c
> > index 5f700719d5c2..b5ea6b312df0 100644
> > --- a/drivers/mtd/nand/sunxi_nand.c
> > +++ b/drivers/mtd/nand/sunxi_nand.c
> > @@ -624,7 +624,7 @@ static u16 sunxi_nfc_randomizer_step(u16 state, int count)
> >  static u16 sunxi_nfc_randomizer_state(struct mtd_info *mtd, int page, bool ecc)
> >  {
> >  	const u16 *seeds = sunxi_nfc_randomizer_page_seeds;
> > -	int mod = mtd->erasesize / mtd->writesize;
> > +	int mod = mtd_div_by_ws(mtd->erasesize, mtd);
> 
> Just a comment (which should not prevent you from applying this patch).
> Isn't it a bit overkill to cast the erasesize to a 64 bit value, and
> then do a do_div on it. Shouldn't happen often though, because
> ->writesize_shift should be != 0 in most (all?) cases.

drivers/mtd/nand/ assumes power-of-2 dimensions for many things, so
probably.

> Another related remark: with the MLC/paired pages stuff I'll have to
> retrieve this information (number of write units per erase block) quite
> often, so maybe we should have a field (and/or an helper) for that.

Perhaps.

Brian

[PATCH v2 3/3] mtd: nand: sunxi: add randomizer support

[Brian Norris]

On Sat, Jan 23, 2016 at 09:18:44AM +0100, Boris Brezillon wrote:
> On Fri, 22 Jan 2016 18:57:13 -0800
> Brian Norris <computersforpeace@gmail.com> wrote:
> > 
> > From: Brian Norris <computersforpeace@gmail.com>
> > Date: Fri, 22 Jan 2016 18:54:02 -0800
> > Subject: [PATCH] mtd: nand: sunxi: use mtd_div_by_ws() helper
> > 
> > Suggested-by: Richard Weinberger <richard@nod.at>
> > Signed-off-by: Brian Norris <computersforpeace@gmail.com>
> 
> Acked-by: Boris Brezillon <boris.brezillon@free-electrons.com>

Applied.

> > ---
> >  drivers/mtd/nand/sunxi_nand.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/mtd/nand/sunxi_nand.c b/drivers/mtd/nand/sunxi_nand.c
> > index 5f700719d5c2..b5ea6b312df0 100644
> > --- a/drivers/mtd/nand/sunxi_nand.c
> > +++ b/drivers/mtd/nand/sunxi_nand.c
> > @@ -624,7 +624,7 @@ static u16 sunxi_nfc_randomizer_step(u16 state, int count)
> >  static u16 sunxi_nfc_randomizer_state(struct mtd_info *mtd, int page, bool ecc)
> >  {
> >  	const u16 *seeds = sunxi_nfc_randomizer_page_seeds;
> > -	int mod = mtd->erasesize / mtd->writesize;
> > +	int mod = mtd_div_by_ws(mtd->erasesize, mtd);
> 
> Just a comment (which should not prevent you from applying this patch).
> Isn't it a bit overkill to cast the erasesize to a 64 bit value, and
> then do a do_div on it. Shouldn't happen often though, because
> ->writesize_shift should be != 0 in most (all?) cases.

drivers/mtd/nand/ assumes power-of-2 dimensions for many things, so
probably.

> Another related remark: with the MLC/paired pages stuff I'll have to
> retrieve this information (number of write units per erase block) quite
> often, so maybe we should have a field (and/or an helper) for that.

Perhaps.

Brian

Re: [PATCH v2 0/3] mtd: nand: add randomizer support

[Boris Brezillon]

Hi Brian,

Anything blocking in this series?
I was expecting to get it into 4.5, but it's too late now. Could you
consider reviewing it (in order to take it into 4.6 if everything is
OK for you)?

The reason I'd like to get this into Linux rather quickly is because I
want to port the sunxi-nand driver to u-boot, and these randomizer
stuff are required on most sunxi boards.
IOW, u-boot users would not understand if I port a NAND driver that
appears to be useless for their board(s) :-/.

Thanks,

Boris

On Wed,  2 Dec 2015 12:01:04 +0100
Boris Brezillon <boris.brezillon@free-electrons.com> wrote:

> Hello,
> 
> This series is a proposal to add support for randomizers (either software
> or hardware) to NAND flash controller drivers.
> 
> The last patch is the sunxi HW randomizer implementation and is just given
> as an example (it won't apply on the MTD tree, because it depends on other
> stuff not yet posted on the MTD ML, but if you want a full overview of the
> NAND Flash controller driver you can take a look at this series [2]).
> 
> I can also provide a software implementation based on LFSR (Left Feedback
> Shift Register) algorithm, thought I haven't tested it yet, hence why it's
> not part of this series. Let me know if you're interested in this
> implementation.
> 
> This series depends on the "per-partition ECC" series [1], because I need
> the randomizer seed to be different depending on the partition (for the
> same reason I needed ECC config to be different for each partition: the
> bootrom config might not fit the NAND chip requirements).
> 
> I'd like to have feedback from both MTD maintainers and driver
> developers who might need to implement (or use) a randomizer in their
> system, so feel free to comment on this series.
> 
> Best Regards,
> 
> Boris
> 
> [1] https://lkml.org/lkml/2014/2/12/627
> [2] https://groups.google.com/forum/#!msg/linux-sunxi/s3lBb01I0Js/z2NoCFJ83g4J 
> 
> Changes since v1:
> - add some comments to explain how the sunxi randomizer works
> - fix a few minor bugs and coding style issues
> 
> Boris Brezillon (3):
>   mtd: nand: add NAND_NEED_SCRAMBLING option flag
>   mtd: nand: add NAND_NEED_SCRAMBLING flag to the H27UCG8T2ATR-BC
>     definition
>   mtd: nand: sunxi: add randomizer support
> 
>  drivers/mtd/nand/nand_ids.c   |   4 +-
>  drivers/mtd/nand/sunxi_nand.c | 287 ++++++++++++++++++++++++++++++++++++++----
>  include/linux/mtd/nand.h      |   6 +
>  3 files changed, 269 insertions(+), 28 deletions(-)
> 



-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

[PATCH v2 0/3] mtd: nand: add randomizer support

[Boris Brezillon]

Hi Brian,

Anything blocking in this series?
I was expecting to get it into 4.5, but it's too late now. Could you
consider reviewing it (in order to take it into 4.6 if everything is
OK for you)?

The reason I'd like to get this into Linux rather quickly is because I
want to port the sunxi-nand driver to u-boot, and these randomizer
stuff are required on most sunxi boards.
IOW, u-boot users would not understand if I port a NAND driver that
appears to be useless for their board(s) :-/.

Thanks,

Boris

On Wed,  2 Dec 2015 12:01:04 +0100
Boris Brezillon <boris.brezillon@free-electrons.com> wrote:

> Hello,
> 
> This series is a proposal to add support for randomizers (either software
> or hardware) to NAND flash controller drivers.
> 
> The last patch is the sunxi HW randomizer implementation and is just given
> as an example (it won't apply on the MTD tree, because it depends on other
> stuff not yet posted on the MTD ML, but if you want a full overview of the
> NAND Flash controller driver you can take a look at this series [2]).
> 
> I can also provide a software implementation based on LFSR (Left Feedback
> Shift Register) algorithm, thought I haven't tested it yet, hence why it's
> not part of this series. Let me know if you're interested in this
> implementation.
> 
> This series depends on the "per-partition ECC" series [1], because I need
> the randomizer seed to be different depending on the partition (for the
> same reason I needed ECC config to be different for each partition: the
> bootrom config might not fit the NAND chip requirements).
> 
> I'd like to have feedback from both MTD maintainers and driver
> developers who might need to implement (or use) a randomizer in their
> system, so feel free to comment on this series.
> 
> Best Regards,
> 
> Boris
> 
> [1] https://lkml.org/lkml/2014/2/12/627
> [2] https://groups.google.com/forum/#!msg/linux-sunxi/s3lBb01I0Js/z2NoCFJ83g4J 
> 
> Changes since v1:
> - add some comments to explain how the sunxi randomizer works
> - fix a few minor bugs and coding style issues
> 
> Boris Brezillon (3):
>   mtd: nand: add NAND_NEED_SCRAMBLING option flag
>   mtd: nand: add NAND_NEED_SCRAMBLING flag to the H27UCG8T2ATR-BC
>     definition
>   mtd: nand: sunxi: add randomizer support
> 
>  drivers/mtd/nand/nand_ids.c   |   4 +-
>  drivers/mtd/nand/sunxi_nand.c | 287 ++++++++++++++++++++++++++++++++++++++----
>  include/linux/mtd/nand.h      |   6 +
>  3 files changed, 269 insertions(+), 28 deletions(-)
> 



-- 
Boris Brezillon, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com