spi: spi-qpic-snand: use correct CW_PER_PAGE value for OOB write

[ Upstream commit 6bc8292 ]

The qcom_spi_program_oob() function uses only the last codeword to write
the OOB data into the flash, but it sets the CW_PER_PAGE field in the
CFG0 register as it would use all codewords.

It seems that this confuses the hardware somehow, and any access to the
flash fails with a timeout error after the function is called. The problem
can be easily reproduced with the following commands:

    # dd if=/dev/zero bs=2176 count=1 > /tmp/test.bin
    1+0 records in
    1+0 records out
    # flash_erase /dev/mtd4 0 0
    Erasing 128 Kibyte @ 0 -- 100 % complete
    # nandwrite -O /dev/mtd4 /tmp/test.bin
    Writing data to block 0 at offset 0x0
    # nanddump -o /dev/mtd4 >/dev/null
    ECC failed: 0
    ECC corrected: 0
    Number of bad blocks: 0
    Number of bbt blocks: 0
    Block size 131072, page size 2048, OOB size 128
    Dumping data starting at 0x00000000 and ending at 0x00020000...
    [   33.197605] qcom_snand 79b0000.spi: failure to read oob
    libmtd: error!: MEMREADOOB64 ioctl failed for mtd4, offset 0 (eraseblock 0)
            error 110 (Operation timed out)
    [   35.277582] qcom_snand 79b0000.spi: failure in submitting cmd descriptor
    libmtd: error!: cannot read 2048 bytes from mtd4 (eraseblock 0, offset 2048)
            error 110 (Operation timed out)
    nanddump: error!: mtd_read

Change the code to use the correct CW_PER_PAGE value to avoid this.

Fixes: 7304d19 ("spi: spi-qpic: add driver for QCOM SPI NAND flash Interface")
Signed-off-by: Gabor Juhos <j4g8y7@gmail.com>
Link: https://patch.msgid.link/20250801-qpic-snand-oob-cwpp-fix-v1-1-f5a41b86af2e@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: juhosg

drivers/spi/spi-qpic-snand.c

@@ -1185,7 +1185,7 @@ static int qcom_spi_program_oob(struct qcom_nand_controller *snandc,
 	u32 cfg0, cfg1, ecc_bch_cfg, ecc_buf_cfg;
 
 	cfg0 = (ecc_cfg->cfg0 & ~CW_PER_PAGE_MASK) |
-	       FIELD_PREP(CW_PER_PAGE_MASK, num_cw - 1);
+	       FIELD_PREP(CW_PER_PAGE_MASK, 0);
 	cfg1 = ecc_cfg->cfg1;
 	ecc_bch_cfg = ecc_cfg->ecc_bch_cfg;
 	ecc_buf_cfg = ecc_cfg->ecc_buf_cfg;