On Mi, 2019-09-11 at 16:49 +0200, Philipp Puschmann wrote: > BD_DONE flag marks ownership of the buffer. When 1 SDMA owns the buffer, > when 0 ARM owns it. When processing the buffers in > sdma_update_channel_loop the ownership of the currently processed buffer > was set to SDMA again before running the callback function of the the > buffer and while the sdma script may be running in parallel. So there was > the possibility to get the buffer overwritten by SDMA before it has been > processed by kernel leading to kind of random errors in the upper layers, > e.g. bluetooth. > > It may be further a good idea to make the status struct member volatile or > access it using writel or similar to rule out that the compiler sets the > BD_DONE flag before the callback routine has finished. > > Signed-off-by: Philipp Puschmann <philipp.puschm...@emlix.com> > --- > drivers/dma/imx-sdma.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c > index a01f4b5d793c..1abb14ff394d 100644 > --- a/drivers/dma/imx-sdma.c > +++ b/drivers/dma/imx-sdma.c > @@ -802,7 +802,6 @@ static void sdma_update_channel_loop(struct sdma_channel > *sdmac) > */ > > desc->chn_real_count = bd->mode.count; > - bd->mode.status |= BD_DONE; > bd->mode.count = desc->period_len; > desc->buf_ptail = desc->buf_tail; > desc->buf_tail = (desc->buf_tail + 1) % desc->num_bd; > @@ -817,6 +816,8 @@ static void sdma_update_channel_loop(struct sdma_channel > *sdmac) > dmaengine_desc_get_callback_invoke(&desc->vd.tx, NULL); > spin_lock(&sdmac->vc.lock);
To address your comment from the second paragraph of the commit message there should be a dma_wmb() here before changing the status flag. Regards, Lucas > + bd->mode.status |= BD_DONE; > + > if (error) > sdmac->status = old_status; > }
