Re: [PATCH 01/14] dma: sun6i-dma: Add burst case of 4

Jean-Francois Moine
2016-10-23T16:31:07Z

On Tue, 4 Oct 2016 18:55:54 +0200
Maxime Ripard <maxime.ripard-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org> wrote:

> On Tue, Oct 04, 2016 at 12:40:11PM +0200, Jean-Francois Moine wrote:
> > On Tue, 4 Oct 2016 11:46:14 +0200
> > Mylène Josserand <mylene.josserand-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org> wrote:
> >
> > > Add the case of a burst of 4 which is handled by the SoC.
> > >
> > > Signed-off-by: Mylène Josserand <mylene.josserand-wi1+55ScJUtKEb57/3fJTNBPR1lH4CV8@public.gmane.org>
> > > ---
> > > drivers/dma/sun6i-dma.c | 2 ++
> > > 1 file changed, 2 insertions(+)
> > >
> > > diff --git a/drivers/dma/sun6i-dma.c b/drivers/dma/sun6i-dma.c
> > > index 8346199..0485204 100644
> > > --- a/drivers/dma/sun6i-dma.c
> > > +++ b/drivers/dma/sun6i-dma.c
> > > @@ -240,6 +240,8 @@ static inline s8 convert_burst(u32 maxburst)
> > > switch (maxburst) {
> > > case 1:
> > > return 0;
> > > + case 4:
> > > + return 1;
> > > case 8:
> > > return 2;
> > > default:
> > > --
> > > 2.9.3
> >
> > This patch has already been rejected by Maxime in the threads
> > http://www.spinics.net/lists/dmaengine/msg08610.html
> > and
> > http://www.spinics.net/lists/dmaengine/msg08719.html
> >
> > I hope you will find the way he wants for this maxburst to be added.
>
> I was talking about something along these lines (not tested):

I wonder why you don't submit this yourself.

> -------8<---------
> diff --git a/drivers/dma/sun6i-dma.c b/drivers/dma/sun6i-dma.c
> index 83461994e418..573ac4608293 100644
> --- a/drivers/dma/sun6i-dma.c
> +++ b/drivers/dma/sun6i-dma.c
> @@ -240,6 +240,8 @@ static inline s8 convert_burst(u32 maxburst)
> switch (maxburst) {
> case 1:
> return 0;
> + case 4:
> + return 1;
> case 8:
> return 2;
> default:
> @@ -1110,11 +1112,19 @@ static int sun6i_dma_probe(struct platform_device *pdev)
> sdc->slave.dst_addr_widths = BIT(DMA_SLAVE_BUSWIDTH_1_BYTE) |
> BIT(DMA_SLAVE_BUSWIDTH_2_BYTES) |
> BIT(DMA_SLAVE_BUSWIDTH_4_BYTES);
> + sdc->slave.dst_bursts = BIT(1) | BIT(8);
> + sdc->slave.src_bursts = BIT(1) | BIT(8);
> sdc->slave.directions = BIT(DMA_DEV_TO_MEM) |
> BIT(DMA_MEM_TO_DEV);
> sdc->slave.residue_granularity = DMA_RESIDUE_GRANULARITY_BURST;
> sdc->slave.dev = &pdev->dev;
>
> + if (of_device_is_compatible(pdev->dev.of_node,
> + "allwinner,sun8i-h3-dma")) {
> + sdc->slave.dst_bursts |= BIT(4);
> + sdc->slave.src_bursts |= BIT(4);
> + }
> +
> sdc->pchans = devm_kcalloc(&pdev->dev, sdc->cfg->nr_max_channels,
> sizeof(struct sun6i_pchan), GFP_KERNEL);
> if (!sdc->pchans)
> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> index cc535a478bae..f7bbec24bb58 100644
> --- a/include/linux/dmaengine.h
> +++ b/include/linux/dmaengine.h
> @@ -673,6 +673,8 @@ struct dma_filter {
> * each type of direction, the dma controller should fill (1 <<
> * <TYPE>) and same should be checked by controller as well
> * @max_burst: max burst capability per-transfer
> + * @dst_bursts: bitfield of the available burst sizes for the destination
> + * @src_bursts: bitfield of the available burst sizes for the source

You did not define dst_bursts nor src_bursts.

> * @residue_granularity: granularity of the transfer residue reported
> * by tx_status
> * @device_alloc_chan_resources: allocate resources and return the
> @@ -800,6 +802,14 @@ struct dma_device {
> static inline int dmaengine_slave_config(struct dma_chan *chan,
> struct dma_slave_config *config)
> {
> + if (config->src_maxburst && config->device->src_bursts &&
> + !(BIT(config->src_maxburst) & config->device->src_bursts))

The maxburst may be as big as 4Kibytes, then, I am not sure that this
code will work!

> + return -EINVAL;
> +
> + if (config->dst_maxburst && config->device->dst_bursts &&
> + !(BIT(config->dst_maxburst) & config->device->dst_bursts))
> + return -EINVAL;
> +
> if (chan->device->device_config)
> return chan->device->device_config(chan, config);
> -------8<------------

Yes, I know that the burst size is always a power of 2.
The best way to check it would be to change the {src,dts}_maxburst to a
bitmap of the possible bursts as 0x0d for 1,4 and 8 bytes. But this
asks for a lot of changes...

--
Ken ar c'hentañ | ** Breizh ha Linux atav! **
Jef | http://moinejf.free.fr/
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