On Wed, Jul 11, 2018 at 07:05:23AM +0000, Robin Gong wrote: > > > > -----Original Message----- > > From: Sascha Hauer [mailto:s.hauer@xxxxxxxxxxxxxx] > > Sent: 2018年7月11日 15:01 > > 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 v1 1/4] dmaengine: imx-sdma: add memcpy interface > > > > On Wed, Jul 11, 2018 at 06:56:18AM +0000, Robin Gong wrote: > > > > > > > -----Original Message----- > > > > From: Sascha Hauer [mailto:s.hauer@xxxxxxxxxxxxxx] > > > > Sent: 2018年7月11日 14:25 > > > > 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 v1 1/4] dmaengine: imx-sdma: add memcpy > > > > interface > > > > > > > > On Wed, Jul 11, 2018 at 12:23:10AM +0800, Robin Gong wrote: > > > > > Add MEMCPY support, meanwhile, add SDMA_BD_MAX_CNT instead of > > > > > '0xffff'. > > > > > > > > > > Signed-off-by: Robin Gong <yibin.gong@xxxxxxx> > > > > > --- > > > > > +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) > > > > > + goto err_out; > > > > > + > > > > > + do { > > > > > + count = min_t(size_t, len, SDMA_BD_MAX_CNT); > > > > > > > > When len is bigger than 0xffff you initialize count to 0xffff... > > > In this case, the data will be split into several bds, for example, If > > > the total count is 0x10000, two bd used then. One is for 0xffff, > > > Another is for the last 1 > > > > And you are doing byte size DMA? Wouldn't word size accesses be more > > optimal? > > > > Sascha > Default is words, and I'll force the buswidth to word and set into BD. > sdma->dma_device.copy_align = DMAENGINE_ALIGN_4_BYTES; So guess which alignment the second transfer has when the first has the size 0xffff. 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
