Re: [PATCH v2] mtd: devices: m25p80: Make sure the buffer passed in op is DMA-able

[Boris Brezillon <boris.brezillon@xxxxxxxxxxx>]

On Tue, 18 Sep 2018 10:59:17 +0300
Jarkko Nikula <jarkko.nikula@xxxxxxxxxxxxxxx> wrote:

> On 09/17/2018 05:31 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 around.
> > 
> > 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).
> > 
> > Changes in v2:
> > - Copy the data from scratchbuf in the ->read_reg() path
> > ---
> >   drivers/mtd/devices/m25p80.c | 26 +++++++++++++++++++++++---
> >   1 file changed, 23 insertions(+), 3 deletions(-)
> >   
> Tested-by: Jarkko Nikula <jarkko.nikula@xxxxxxxxxxxxxxx>
> Reviewed-by: Jarkko Nikula <jarkko.nikula@xxxxxxxxxxxxxxx>

Queued to mtd/master. Thanks for testing and reviewing the patch.

Regards,

Boris


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