On Mon, 17 Sep 2018 17:13:32 +0300
Jarkko Nikula <jarkko.nikula@xxxxxxxxxxxxxxx> wrote:
> On 09/17/2018 04:36 PM, Boris Brezillon wrote:
> > As documented in spi-mem.h, spi_mem_op->data.buf.{in,out} must be
> > DMA-able, and commit 4120f8d158ef ("mtd: spi-nor: Use the spi_mem_xx()
> > API") failed to follow this rule as buffers passed to
> > ->{read,write}_reg() are usually placed on the stack.
> >
> > Fix that by allocating a scratch buffer and copying the data in there
> > before passing it to the spi-mem layer.
> >
> > Fixes: 4120f8d158ef ("mtd: spi-nor: Use the spi_mem_xx() API")
> > Reported-by: Jarkko Nikula <jarkko.nikula@xxxxxxxxxxxxxxx>
> > Cc: <stable@xxxxxxxxxxxxxxx>
> > Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxx>
> > ---
> > Note that the ->{read,write}() path is still buggy since nothing
> > guarantees that buffers passed by the MTD layer to the SPI NOR layer
> > are DMA-able, but this is a long-standing issue which we'll have to
> > address at the spi-nor level (this layer can choose the bounce buffer
> > size based on nor->page_size).
> > ---
> > drivers/mtd/devices/m25p80.c | 24 +++++++++++++++++++++---
> > 1 file changed, 21 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/mtd/devices/m25p80.c b/drivers/mtd/devices/m25p80.c
> > index cbfafc453274..3b7fafa4bbd6 100644
> > --- a/drivers/mtd/devices/m25p80.c
> > +++ b/drivers/mtd/devices/m25p80.c
> > @@ -39,14 +39,22 @@ static int m25p80_read_reg(struct spi_nor *nor, u8 code, u8 *val, int len)
> > struct spi_mem_op op = SPI_MEM_OP(SPI_MEM_OP_CMD(code, 1),
> > SPI_MEM_OP_NO_ADDR,
> > SPI_MEM_OP_NO_DUMMY,
> > - SPI_MEM_OP_DATA_IN(len, val, 1));
> > + SPI_MEM_OP_DATA_IN(len, NULL, 1));
> > + void *scratchbuf;
> > int ret;
> >
> > + scratchbuf = kmemdup(val, len, GFP_KERNEL);
> > + if (!scratchbuf)
> > + return -ENOMEM;
> > +
> > + op.data.buf.in = scratchbuf;
> > ret = spi_mem_exec_op(flash->spimem, &op);
> > if (ret < 0)
> > dev_err(&flash->spimem->spi->dev, "error %d reading %x\n", ret,
> > code);
> >
> > + kfree(scratchbuf);
> > +
>
> Actually this makes things even worse: "unrecognized JEDEC id bytes: b1,
> 74, 01" since we don't copy scratchbuf to original buffer and kmemdup
> before bus read is needless :-)
True :-).
I'll fix that and send a v2.
