[PATCH v4] mtd: gpmi: add NAND write verify support

[Huang Shijie]

Add NAND write verify support in gpmi-nand driver.

This patch fixes a kernel crash when we select
CONFIG_MTD_NAND_VERIFY_WRITE=y, and do some write tests:

root at freescale /$ dd if=/dev/zero of=/dev/mtd0 bs=128k count=1
[   41.070000] Unable to handle kernel NULL pointer dereference at virtual addr0
[   41.080000] pgd = c77ac000
[   41.080000] [00000000] *pgd=4773c831, *pte=00000000, *ppte=00000000
[   41.090000] Internal error: Oops: 17 [#1] ARM
[   41.090000] Modules linked in:
[   41.090000] CPU: 0    Not tainted (3.6.0-rc1-next-20120809-00002-ga25d017-d)
[   41.090000] PC is at nand_verify_buf+0x18/0x5c
[   41.090000] LR is at nand_write_page+0xc0/0x140
[   41.090000] pc : [<c023e7d4>]    lr : [<c023fcfc>]    psr: 20000013
[   41.090000] sp : c7779de4  ip : 00000000  fp : c6e60000
[   41.090000] r10: 00000000  r9 : 00020000  r8 : 00000000
[   41.090000] r7 : 00000000  r6 : c6e60000  r5 : c762cb10  r4 : 00000000
[   41.090000] r3 : c762c8a8  r2 : 00000800  r1 : c6e60000  r0 : 00000000
[   41.090000] Flags: nzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
[   41.090000] Control: 0005317f  Table: 477ac000  DAC: 00000015
[   41.090000] Process dd (pid: 427, stack limit = 0xc7778270)
[   41.090000] Stack: (0xc7779de4 to 0xc777a000)
	...

	The crash log is fetched from Fabio's patch. thanks to Fabio's hard work.

Cc: <stable at vger.kernel.org>
Reported-by: Fabio Estevam <fabio.estevam at freescale.com>
Signed-off-by: Huang Shijie <shijie8 at gmail.com>
---
v3 --> v4:
    [1] add credit to Fabio.

v2 --> v3:
    [1] free the verify_buf when we exit.

v1 --> v2:
    [1] use the mtd->writesize to allocate the verify buffer.
    [2] add new field `verify_buf` in gpmi_nand_data{}

    tested this patch on imx6q-arm2 board.
---
 drivers/mtd/nand/gpmi-nand/gpmi-nand.c |   25 +++++++++++++++++++++++++
 drivers/mtd/nand/gpmi-nand/gpmi-nand.h |    1 +
 2 files changed, 26 insertions(+), 0 deletions(-)

diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
index 8c0d2f0..e1e4c51 100644
--- a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
+++ b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
@@ -1512,12 +1512,34 @@ static int gpmi_pre_bbt_scan(struct gpmi_nand_data  *this)
 	return nand_boot_init(this);
 }
 
+static int gpmi_verify_buf(struct mtd_info *mtd, const uint8_t *buf, int len)
+{
+	struct nand_chip *chip = mtd->priv;
+	struct gpmi_nand_data *this = chip->priv;
+	int ret;
+
+	ret = chip->ecc.read_page(mtd, chip, this->verify_buf, 0, 0);
+	if (ret)
+		return -EFAULT;
+	if (memcmp(buf, this->verify_buf, len))
+		return -EFAULT;
+	return 0;
+}
+
 static int gpmi_scan_bbt(struct mtd_info *mtd)
 {
 	struct nand_chip *chip = mtd->priv;
 	struct gpmi_nand_data *this = chip->priv;
 	int ret;
 
+	/*
+	 * We have gotten the right page size now, use it to allocate
+	 * the proper verify buffer.
+	 */
+	this->verify_buf = kzalloc(mtd->writesize, GFP_KERNEL);
+	if (!this->verify_buf)
+		return -ENOMEM;
+
 	/* Prepare for the BBT scan. */
 	ret = gpmi_pre_bbt_scan(this);
 	if (ret)
@@ -1531,6 +1553,8 @@ void gpmi_nfc_exit(struct gpmi_nand_data *this)
 {
 	nand_release(&this->mtd);
 	gpmi_free_dma_buffer(this);
+	kfree(this->verify_buf);
+	this->verify_buf = NULL;
 }
 
 static int __devinit gpmi_nfc_init(struct gpmi_nand_data *this)
@@ -1556,6 +1580,7 @@ static int __devinit gpmi_nfc_init(struct gpmi_nand_data *this)
 	chip->read_byte		= gpmi_read_byte;
 	chip->read_buf		= gpmi_read_buf;
 	chip->write_buf		= gpmi_write_buf;
+	chip->verify_buf	= gpmi_verify_buf;
 	chip->ecc.read_page	= gpmi_ecc_read_page;
 	chip->ecc.write_page	= gpmi_ecc_write_page;
 	chip->ecc.read_oob	= gpmi_ecc_read_oob;
diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-nand.h b/drivers/mtd/nand/gpmi-nand/gpmi-nand.h
index 1547a60..8ddf115 100644
--- a/drivers/mtd/nand/gpmi-nand/gpmi-nand.h
+++ b/drivers/mtd/nand/gpmi-nand/gpmi-nand.h
@@ -144,6 +144,7 @@ struct gpmi_nand_data {
 	/* MTD / NAND */
 	struct nand_chip	nand;
 	struct mtd_info		mtd;
+	uint8_t			*verify_buf;
 
 	/* General-use Variables */
 	int			current_chip;
-- 
1.7.4.4