Messages in this thread | | | Date | Wed, 26 Jul 2023 11:36:23 +0530 | Subject | Re: [PATCH 1/2] spi: spi-qcom-qspi: Fallback to PIO for xfers that aren't multiples of 4 bytes | From | Vijaya Krishna Nivarthi <> |
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On 7/25/2023 11:32 PM, Douglas Anderson wrote: > 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>
Thank you for the fix,
Vijay/
> --- > > drivers/spi/spi-qcom-qspi.c | 12 ++++++++++++ > 1 file changed, 12 insertions(+) > > diff --git a/drivers/spi/spi-qcom-qspi.c b/drivers/spi/spi-qcom-qspi.c > index a0ad9802b606..39b4d8a8107a 100644 > --- a/drivers/spi/spi-qcom-qspi.c > +++ b/drivers/spi/spi-qcom-qspi.c > @@ -355,10 +355,22 @@ 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++) {
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