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    Subject[PATCH 4.14 21/67] mtd: spi-nor: Fix Cadence QSPI page fault kernel panic
    Date
    4.14-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    [ Upstream commit a6a66f80c85e8e20573ca03fabf32445954a88d5 ]

    The current Cadence QSPI driver caused a kernel panic sporadically
    when writing to QSPI. The problem was caused by writing more bytes
    than needed because the QSPI operated on 4 bytes at a time.
    <snip>
    [ 11.202044] Unable to handle kernel paging request at virtual address bffd3000
    [ 11.209254] pgd = e463054d
    [ 11.211948] [bffd3000] *pgd=2fffb811, *pte=00000000, *ppte=00000000
    [ 11.218202] Internal error: Oops: 7 [#1] SMP ARM
    [ 11.222797] Modules linked in:
    [ 11.225844] CPU: 1 PID: 1317 Comm: systemd-hwdb Not tainted 4.17.7-d0c45cd44a8f
    [ 11.235796] Hardware name: Altera SOCFPGA Arria10
    [ 11.240487] PC is at __raw_writesl+0x70/0xd4
    [ 11.244741] LR is at cqspi_write+0x1a0/0x2cc
    </snip>
    On a page boundary limit the number of bytes copied from the tx buffer
    to remain within the page.

    This patch uses a temporary buffer to hold the 4 bytes to write and then
    copies only the bytes required from the tx buffer.

    Reported-by: Adrian Amborzewicz <adrian.ambrozewicz@intel.com>
    Signed-off-by: Thor Thayer <thor.thayer@linux.intel.com>
    Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    drivers/mtd/spi-nor/cadence-quadspi.c | 19 ++++++++++++++++---
    1 file changed, 16 insertions(+), 3 deletions(-)

    diff --git a/drivers/mtd/spi-nor/cadence-quadspi.c b/drivers/mtd/spi-nor/cadence-quadspi.c
    index 8d89204b90d2..f22dd34f4f83 100644
    --- a/drivers/mtd/spi-nor/cadence-quadspi.c
    +++ b/drivers/mtd/spi-nor/cadence-quadspi.c
    @@ -625,9 +625,23 @@ static int cqspi_indirect_write_execute(struct spi_nor *nor,
    reg_base + CQSPI_REG_INDIRECTWR);

    while (remaining > 0) {
    + size_t write_words, mod_bytes;
    +
    write_bytes = remaining > page_size ? page_size : remaining;
    - iowrite32_rep(cqspi->ahb_base, txbuf,
    - DIV_ROUND_UP(write_bytes, 4));
    + write_words = write_bytes / 4;
    + mod_bytes = write_bytes % 4;
    + /* Write 4 bytes at a time then single bytes. */
    + if (write_words) {
    + iowrite32_rep(cqspi->ahb_base, txbuf, write_words);
    + txbuf += (write_words * 4);
    + }
    + if (mod_bytes) {
    + unsigned int temp = 0xFFFFFFFF;
    +
    + memcpy(&temp, txbuf, mod_bytes);
    + iowrite32(temp, cqspi->ahb_base);
    + txbuf += mod_bytes;
    + }

    ret = wait_for_completion_timeout(&cqspi->transfer_complete,
    msecs_to_jiffies
    @@ -638,7 +652,6 @@ static int cqspi_indirect_write_execute(struct spi_nor *nor,
    goto failwr;
    }

    - txbuf += write_bytes;
    remaining -= write_bytes;

    if (remaining > 0)
    --
    2.19.1


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