diff options
| author | Douglas Anderson | 2023-07-25 11:02:26 -0700 |
|---|---|---|
| committer | Mark Brown | 2023-07-26 12:47:19 +0100 |
| commit | 138d73b627c71bf2b2f61502dc6c1137b9656434 (patch) | |
| tree | 67c47d624e6f1a804614c255d6bc06308a3b9b54 /drivers/spi | |
| parent | 916a4edf3daed845b1e5d6cf0578a7e43c6f520e (diff) | |
spi: spi-qcom-qspi: Fallback to PIO for xfers that aren't multiples of 4 bytes
The Qualcomm QSPI driver appears to require that any reads using DMA
are a mutliple of 4 bytes. If this isn't true then the controller will
clobber any extra bytes in memory following the last word. Let's
detect this and falback to PIO.
This fixes problems reported by slub_debug=FZPUA, which would complain
about "kmalloc Redzone overwritten". One such instance said:
0xffffff80c29d541a-0xffffff80c29d541b @offset=21530. First byte 0x0 instead of 0xcc
Allocated in mtd_kmalloc_up_to+0x98/0xac age=36 cpu=3 pid=6658
Tracing through what was happening I saw that, while we often did DMA
tranfers of 0x1000 bytes, sometimes we'd end up doing ones of 0x41a
bytes. Those 0x41a byte transfers were the problem.
NOTE: a future change will enable the SPI "mem ops" to help avoid this
case, but it still seems good to add the extra check in the transfer.
Fixes: b5762d95607e ("spi: spi-qcom-qspi: Add DMA mode support")
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Vijaya Krishna Nivarthi <quic_vnivarth@quicinc.com>
Reviewed-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230725110226.1.Ia2f980fc7cd0b831e633391f0bb1272914d8f381@changeid
Signed-off-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to 'drivers/spi')
| -rw-r--r-- | drivers/spi/spi-qcom-qspi.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/drivers/spi/spi-qcom-qspi.c b/drivers/spi/spi-qcom-qspi.c index 9b3092e22942..db1dd133762e 100644 --- a/drivers/spi/spi-qcom-qspi.c +++ b/drivers/spi/spi-qcom-qspi.c @@ -357,10 +357,22 @@ static int qcom_qspi_setup_dma_desc(struct qcom_qspi *ctrl, for (i = 0; i < sgt->nents; i++) { dma_ptr_sg = sg_dma_address(sgt->sgl + i); + dma_len_sg = sg_dma_len(sgt->sgl + i); if (!IS_ALIGNED(dma_ptr_sg, QSPI_ALIGN_REQ)) { dev_warn_once(ctrl->dev, "dma_address not aligned to %d\n", QSPI_ALIGN_REQ); return -EAGAIN; } + /* + * When reading with DMA the controller writes to memory 1 word + * at a time. If the length isn't a multiple of 4 bytes then + * the controller can clobber the things later in memory. + * Fallback to PIO to be safe. + */ + if (ctrl->xfer.dir == QSPI_READ && (dma_len_sg & 0x03)) { + dev_warn_once(ctrl->dev, "fallback to PIO for read of size %#010x\n", + dma_len_sg); + return -EAGAIN; + } } for (i = 0; i < sgt->nents; i++) { |