Am Dienstag, den 24.07.2018, 01:46 +0800 schrieb Robin Gong: > If multi-bds used in one transfer, all bds should be consisten > memory.To easily follow it, enlarge the dma pool size into 20 bds, > and it will report error if the number of bds is over than 20. For > dmatest, the max count for single transfer is NUM_BD * > SDMA_BD_MAX_CNT = 20 * 65535 = ~1.28MB. Both the commit message and the comment need a lot more care to actually tell what this commit is trying to achieve. Currently I don't follow at all. What does "consisten" mean? Do you mean BDs should be contiguous in memory? What do you gain by over-allocating each BD by a factor of 20? Regards, Lucas > Signed-off-by: Robin Gong <yibin.gong@xxxxxxx> > --- > drivers/dma/imx-sdma.c | 17 ++++++++++++++++- > 1 file changed, 16 insertions(+), 1 deletion(-) > > diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c > index b4ec2d2..5973489 100644 > --- a/drivers/dma/imx-sdma.c > +++ b/drivers/dma/imx-sdma.c > @@ -298,6 +298,15 @@ struct sdma_context_data { > > u32 scratch7; > } __attribute__ ((packed)); > > +/* > + * All bds in one transfer should be consitent on SDMA. To easily follow it,just > + * set the dma pool size as the enough bds. For example, in dmatest case, the > + * max 20 bds means the max for single transfer is NUM_BD * SDMA_BD_MAX_CNT = 20 > + * * 65535 = ~1.28MB. 20 bds supposed to be enough basically.If it's still not > + * enough in some specific cases, enlarge it here.Warning message would also > + * appear if the bd numbers is over than 20. > + */ > +#define NUM_BD 20 > > struct sdma_engine; > > @@ -1273,7 +1282,7 @@ static int sdma_alloc_chan_resources(struct dma_chan *chan) > > goto disable_clk_ahb; > > > sdmac->bd_pool = dma_pool_create("bd_pool", chan->device->dev, > > - sizeof(struct sdma_buffer_descriptor), > > + NUM_BD * sizeof(struct sdma_buffer_descriptor), > > 32, 0); > > > return 0; > @@ -1314,6 +1323,12 @@ static struct sdma_desc *sdma_transfer_init(struct sdma_channel *sdmac, > { > > struct sdma_desc *desc; > > > + if (bds > NUM_BD) { > > + dev_err(sdmac->sdma->dev, "%d bds exceed the max %d\n", > > + bds, NUM_BD); > > + goto err_out; > > + } > + > > desc = kzalloc((sizeof(*desc)), GFP_NOWAIT); > > if (!desc) > > goto err_out; -- 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