On Fri, Jul 20, 2018 at 09:40:51AM +0000, Robin Gong wrote: > > -----Original Message----- > > From: Sascha Hauer [mailto:s.hauer@xxxxxxxxxxxxxx] > > Sent: 2018年7月13日 14:16 > > To: Robin Gong <yibin.gong@xxxxxxx> > > Cc: vkoul@xxxxxxxxxx; dan.j.williams@xxxxxxxxx; shawnguo@xxxxxxxxxx; Fabio > > Estevam <fabio.estevam@xxxxxxx>; linux@xxxxxxxxxxxxxxx; > > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; kernel@xxxxxxxxxxxxxx; > > dmaengine@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; dl-linux-imx > > <linux-imx@xxxxxxx> > > Subject: Re: [PATCH v2 2/3] dmaengine: imx-sdma: add memcpy interface > > > > On Fri, Jul 13, 2018 at 09:08:46PM +0800, Robin Gong wrote: > > > Add MEMCPY capability for imx-sdma driver. > > > > > > Signed-off-by: Robin Gong <yibin.gong@xxxxxxx> > > > --- > > > drivers/dma/imx-sdma.c | 95 > > > ++++++++++++++++++++++++++++++++++++++++++++++++-- > > > 1 file changed, 92 insertions(+), 3 deletions(-) > > > > > > @@ -1318,6 +1347,63 @@ static struct sdma_desc > > *sdma_transfer_init(struct sdma_channel *sdmac, > > > return NULL; > > > } > > > > > > +static struct dma_async_tx_descriptor *sdma_prep_memcpy( > > > + struct dma_chan *chan, dma_addr_t dma_dst, > > > + dma_addr_t dma_src, size_t len, unsigned long flags) { > > > + struct sdma_channel *sdmac = to_sdma_chan(chan); > > > + struct sdma_engine *sdma = sdmac->sdma; > > > + int channel = sdmac->channel; > > > + size_t count; > > > + int i = 0, param; > > > + struct sdma_buffer_descriptor *bd; > > > + struct sdma_desc *desc; > > > + > > > + if (!chan || !len) > > > + return NULL; > > > + > > > + dev_dbg(sdma->dev, "memcpy: %pad->%pad, len=%zu, channel=%d.\n", > > > + &dma_src, &dma_dst, len, channel); > > > + > > > + desc = sdma_transfer_init(sdmac, DMA_MEM_TO_MEM, > > > + len / SDMA_BD_MAX_CNT + 1); > > > + if (!desc) > > > + return NULL; > > > + > > > + do { > > > + count = min_t(size_t, len, SDMA_BD_MAX_CNT); > > > + bd = &desc->bd[i]; > > > + bd->buffer_addr = dma_src; > > > + bd->ext_buffer_addr = dma_dst; > > > + bd->mode.count = count; > > > + desc->chn_count += count; > > > + /* align with sdma->dma_device.copy_align: 4bytes */ > > > + bd->mode.command = 0; > > > + > > > + dma_src += count; > > > + dma_dst += count; > > > + len -= count; > > > + i++; > > > > NACK. > > > > Please actually look at your code and find out where you do unaligned DMA > > accesses. Hint: What happens when this loop body is executed more than > > once? > > > > Sascha > Actually internal sdma script has already take such 'align' matter like below: > Burst with words if source/dest address and data length are all aligned with words, burst with > Byte if not. If that's the case why did you add the DMAENGINE_ALIGN_4_BYTES flag in the first place? Also, if the SDMA script falls back to byte copy when necessary, doing so probably has performance impacts, so I wonder why you don't just cut 'count' to something that is four byte aligned. Sascha -- Pengutronix e.K. | | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | -- 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
