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SubjectRE: [PATCH v2 2/3] dmaengine: imx-sdma: add memcpy interface
Date
> -----Original Message-----
> From: Sascha Hauer [mailto:s.hauer@pengutronix.de]
> Sent: 2018年7月13日 14:16
> To: Robin Gong <yibin.gong@nxp.com>
> Cc: vkoul@kernel.org; dan.j.williams@intel.com; shawnguo@kernel.org; Fabio
> Estevam <fabio.estevam@nxp.com>; linux@armlinux.org.uk;
> linux-arm-kernel@lists.infradead.org; kernel@pengutronix.de;
> dmaengine@vger.kernel.org; linux-kernel@vger.kernel.org; dl-linux-imx
> <linux-imx@nxp.com>
> 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@nxp.com>
> > ---
> > 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. So I will remove the comment '/* align with sdma->dma_device.copy_align: 4bytes */'
In v3. Besides, I have found another bug which introduced by my virt-dma patch. Will send
V3 later.
>
> > +
> > + param = BD_DONE | BD_EXTD | BD_CONT;
> > + /* last bd */
> > + if (!len) {
> > + param |= BD_INTR;
> > + param |= BD_LAST;
> > + param &= ~BD_CONT;
> > + }
> > +
> > + dev_dbg(sdma->dev, "entry %d: count: %zd dma: 0x%x %s%s\n",
> > + i, count, bd->buffer_addr,
> > + param & BD_WRAP ? "wrap" : "",
> > + param & BD_INTR ? " intr" : "");
> > +
> > + bd->mode.status = param;
> > + } while (len);
> > +
>
> --
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