On Wed, Jun 08, 2016 at 09:51:57AM +0100, Jon Hunter wrote: > Hi Peter, > > On 07/06/16 18:38, Peter Griffin wrote: > > There is no point calculating the residue if there is > > no txstate to store the value. > > > > Signed-off-by: Peter Griffin <peter.griffin@xxxxxxxxxx> > > --- > > drivers/dma/tegra20-apb-dma.c | 2 +- > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c > > index 01e316f..7f4af8c 100644 > > --- a/drivers/dma/tegra20-apb-dma.c > > +++ b/drivers/dma/tegra20-apb-dma.c > > @@ -814,7 +814,7 @@ static enum dma_status tegra_dma_tx_status(struct dma_chan *dc, > > unsigned int residual; > > > > ret = dma_cookie_status(dc, cookie, txstate); > > - if (ret == DMA_COMPLETE) > > + if (ret == DMA_COMPLETE || !txstate) > > return ret; > > Thanks for reporting this. I agree that we should not do this, however, > looking at the code for Tegra, I am wondering if this could change the > actual state that is returned. Looking at dma_cookie_status() it will > call dma_async_is_complete() which will return either DMA_COMPLETE or > DMA_IN_PROGRESS. It could be possible that the actual state for the > DMA transfer in the tegra driver is DMA_ERROR, so I am wondering if we > should do something like the following ... This one is stopping code execution when residue is not valid. Do notice that it check for DMA_COMPLETE OR txstate. In other cases, wit will return 'that' state when txstate is NULL. I am going to apply this. > > diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c > index 01e316f73559..45edab7418d0 100644 > --- a/drivers/dma/tegra20-apb-dma.c > +++ b/drivers/dma/tegra20-apb-dma.c > @@ -822,13 +822,8 @@ static enum dma_status tegra_dma_tx_status(struct dma_chan *dc, > /* Check on wait_ack desc status */ > list_for_each_entry(dma_desc, &tdc->free_dma_desc, node) { > if (dma_desc->txd.cookie == cookie) { > - residual = dma_desc->bytes_requested - > - (dma_desc->bytes_transferred % > - dma_desc->bytes_requested); > - dma_set_residue(txstate, residual); > ret = dma_desc->dma_status; > - spin_unlock_irqrestore(&tdc->lock, flags); > - return ret; > + goto found; > } > } > > @@ -836,17 +831,23 @@ static enum dma_status tegra_dma_tx_status(struct dma_chan *dc, > list_for_each_entry(sg_req, &tdc->pending_sg_req, node) { > dma_desc = sg_req->dma_desc; > if (dma_desc->txd.cookie == cookie) { > - residual = dma_desc->bytes_requested - > - (dma_desc->bytes_transferred % > - dma_desc->bytes_requested); > - dma_set_residue(txstate, residual); > ret = dma_desc->dma_status; > - spin_unlock_irqrestore(&tdc->lock, flags); > - return ret; > + goto found; > } > } > > - dev_dbg(tdc2dev(tdc), "cookie %d does not found\n", cookie); > + dev_warn(tdc2dev(tdc), "cookie %d not found\n", cookie); > + spin_unlock_irqrestore(&tdc->lock, flags); > + return ret; > + > +found: > + if (txstate) { > + residual = dma_desc->bytes_requested - > + (dma_desc->bytes_transferred % > + dma_desc->bytes_requested); > + dma_set_residue(txstate, residual); > + } > + I feel this optimizes stuff, which seems okay. Feel free to send as proper patch. > spin_unlock_irqrestore(&tdc->lock, flags); > return ret; > } > > Cheers > Jon > > -- > nvpublic -- ~Vinod -- To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html