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SubjectRe: [PATCH 6/7 v2] dma: sh: provide a migration path for slave drivers to stop using .private
Hi Vinod

On Mon, 16 Jul 2012, Vinod Koul wrote:

> On Thu, 2012-07-05 at 12:29 +0200, Guennadi Liakhovetski wrote:
> > This patch extends the sh dmaengine driver to support the preferred channel
> > selection and configuration method, instead of using the "private" field
> > from struct dma_chan. We add a standard filter function to be used by
> > slave drivers instead of implementing their own ones, and add support for
> > the DMA_SLAVE_CONFIG control operation, which must accompany the new
> > channel selection method. We still support the legacy .private channel
> > allocation method to cater for a smooth driver migration.
> There seem to be two things done in this patch, one is to provide a
> filter function for people to use for channel filtering, and second the
> removal of .private. It would be good to split these two.

No, please, see the patch description. This patch only provides a filter
function. It does _not_ remove the use of .private yet. First all client
drivers have to be ported over to use the new filter + slave-config
scheme, only then will the driver be able to drop support for .private.

> > Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
> > ---
> > drivers/dma/sh/shdma-base.c | 114 +++++++++++++++++++++++++++++++++---------
> > drivers/dma/sh/shdma.c | 5 +-
> > include/linux/sh_dma.h | 2 +
> > include/linux/shdma-base.h | 2 +-
> > 4 files changed, 95 insertions(+), 28 deletions(-)
> >
> > diff --git a/drivers/dma/sh/shdma-base.c b/drivers/dma/sh/shdma-base.c
> > index 73db282..0c34c73 100644
> > --- a/drivers/dma/sh/shdma-base.c
> > +++ b/drivers/dma/sh/shdma-base.c
> > @@ -171,6 +171,65 @@ static struct shdma_desc *shdma_get_desc(struct shdma_chan *schan)
> > return NULL;
> > }
> >
> > +static int shdma_setup_slave(struct shdma_chan *schan, int slave_id)
> > +{
> > + struct shdma_dev *sdev = to_shdma_dev(schan->dma_chan.device);
> > + const struct shdma_ops *ops = sdev->ops;
> > + int ret;
> > +
> > + if (slave_id < 0 || slave_id >= slave_num)
> > + return -EINVAL;
> > +
> > + if (test_and_set_bit(slave_id, shdma_slave_used))
> > + return -EBUSY;
> > +
> > + ret = ops->set_slave(schan, slave_id, false);
> > + if (ret < 0) {
> > + clear_bit(slave_id, shdma_slave_used);
> > + return ret;
> > + }
> > +
> > + schan->slave_id = slave_id;
> > +
> > + return 0;
> > +}
> > +
> > +/*
> > + * This is the standard shdma filter function to be used as a replacement to the
> > + * "old" method, using the .private pointer. If for some reason you allocate a
> > + * channel without slave data, use something like ERR_PTR(-EINVAL) as a filter
> > + * parameter. If this filter is used, the slave driver, after calling
> > + * dma_request_channel(), will also have to call dmaengine_slave_config() with
> > + * .slave_id, .direction, and either .src_addr or .dst_addr set.
> > + * NOTE: this filter doesn't support multiple DMAC drivers with the DMA_SLAVE
> > + * capability! If this becomes a requirement, hardware glue drivers, using this
> > + * services would have to provide their own filters, which first would check
> > + * the device driver, similar to how other DMAC drivers, e.g., sa11x0-dma.c, do
> > + * this, and only then, in case of a match, call this common filter.
> > + */
> > +bool shdma_chan_filter(struct dma_chan *chan, void *arg)
> > +{
> > + struct shdma_chan *schan = to_shdma_chan(chan);
> > + struct shdma_dev *sdev = to_shdma_dev(schan->dma_chan.device);
> > + const struct shdma_ops *ops = sdev->ops;
> > + int slave_id = (int)arg;
> > + int ret;
> > +
> > + if (slave_id < 0)
> > + /* No slave requested - arbitrary channel */
> > + return true;
> > +
> > + if (slave_id >= slave_num)
> > + return false;
> > +
> > + ret = ops->set_slave(schan, slave_id, true);
> > + if (ret < 0)
> > + return false;
> > +
> > + return true;
> > +}
> > +EXPORT_SYMBOL(shdma_chan_filter);
> > +
> > static int shdma_alloc_chan_resources(struct dma_chan *chan)
> > {
> > struct shdma_chan *schan = to_shdma_chan(chan);
> > @@ -185,21 +244,10 @@ static int shdma_alloc_chan_resources(struct dma_chan *chan)
> > * never runs concurrently with itself or free_chan_resources.
> > */
> > if (slave) {
> > - if (slave->slave_id < 0 || slave->slave_id >= slave_num) {
> > - ret = -EINVAL;
> > - goto evalid;
> > - }
> > -
> > - if (test_and_set_bit(slave->slave_id, shdma_slave_used)) {
> > - ret = -EBUSY;
> > - goto etestused;
> > - }
> > -
> > - ret = ops->set_slave(schan, slave->slave_id);
> > + /* Legacy mode: .private is set in filter */
> > + ret = shdma_setup_slave(schan, slave->slave_id);
> > if (ret < 0)
> > goto esetslave;
> > -
> > - schan->slave_id = slave->slave_id;
> > } else {
> > schan->slave_id = -EINVAL;
> > }
> > @@ -228,8 +276,6 @@ edescalloc:
> > if (slave)
> > esetslave:
> > clear_bit(slave->slave_id, shdma_slave_used);
> > -etestused:
> > -evalid:
> > chan->private = NULL;
> you missed this one

Please, see above.

Thanks
Guennadi

> > return ret;
> > }
> > @@ -587,22 +633,40 @@ static int shdma_control(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
> > struct shdma_chan *schan = to_shdma_chan(chan);
> > struct shdma_dev *sdev = to_shdma_dev(chan->device);
> > const struct shdma_ops *ops = sdev->ops;
> > + struct dma_slave_config *config;
> > unsigned long flags;
> > -
> > - /* Only supports DMA_TERMINATE_ALL */
> > - if (cmd != DMA_TERMINATE_ALL)
> > - return -ENXIO;
> > + int ret;
> >
> > if (!chan)
> > return -EINVAL;
> >
> > - spin_lock_irqsave(&schan->chan_lock, flags);
> > -
> > - ops->halt_channel(schan);
> > -
> > - spin_unlock_irqrestore(&schan->chan_lock, flags);
> > + switch (cmd) {
> > + case DMA_TERMINATE_ALL:
> > + spin_lock_irqsave(&schan->chan_lock, flags);
> > + ops->halt_channel(schan);
> > + spin_unlock_irqrestore(&schan->chan_lock, flags);
> >
> > - shdma_chan_ld_cleanup(schan, true);
> > + shdma_chan_ld_cleanup(schan, true);
> > + break;
> > + case DMA_SLAVE_CONFIG:
> > + /*
> > + * So far only .slave_id is used, but the slave drivers are
> > + * encouraged to also set a transfer direction and an address.
> > + */
> > + if (!arg)
> > + return -EINVAL;
> > + /*
> > + * We could lock this, but you shouldn't be configuring the
> > + * channel, while using it...
> > + */
> > + config = (struct dma_slave_config*)arg;
> > + ret = shdma_setup_slave(schan, config->slave_id);
> > + if (ret < 0)
> > + return ret;
> > + break;
> > + default:
> > + return -ENXIO;
> > + }
> >
> > return 0;
> > }
> > diff --git a/drivers/dma/sh/shdma.c b/drivers/dma/sh/shdma.c
> > index 9a10d8b..027c9be 100644
> > --- a/drivers/dma/sh/shdma.c
> > +++ b/drivers/dma/sh/shdma.c
> > @@ -320,7 +320,7 @@ static const struct sh_dmae_slave_config *dmae_find_slave(
> > }
> >
> > static int sh_dmae_set_slave(struct shdma_chan *schan,
> > - int slave_id)
> > + int slave_id, bool try)
> > {
> > struct sh_dmae_chan *sh_chan = container_of(schan, struct sh_dmae_chan,
> > shdma_chan);
> > @@ -328,7 +328,8 @@ static int sh_dmae_set_slave(struct shdma_chan *schan,
> > if (!cfg)
> > return -ENODEV;
> >
> > - sh_chan->config = cfg;
> > + if (!try)
> > + sh_chan->config = cfg;
> >
> > return 0;
> > }
> > diff --git a/include/linux/sh_dma.h b/include/linux/sh_dma.h
> > index 4e83f3e..b64d6be 100644
> > --- a/include/linux/sh_dma.h
> > +++ b/include/linux/sh_dma.h
> > @@ -99,4 +99,6 @@ struct sh_dmae_pdata {
> > #define CHCR_TE 0x00000002
> > #define CHCR_IE 0x00000004
> >
> > +bool shdma_chan_filter(struct dma_chan *chan, void *arg);
> > +
> > #endif
> > diff --git a/include/linux/shdma-base.h b/include/linux/shdma-base.h
> > index 6263ad2..93f9821 100644
> > --- a/include/linux/shdma-base.h
> > +++ b/include/linux/shdma-base.h
> > @@ -93,7 +93,7 @@ struct shdma_ops {
> > dma_addr_t (*slave_addr)(struct shdma_chan *);
> > int (*desc_setup)(struct shdma_chan *, struct shdma_desc *,
> > dma_addr_t, dma_addr_t, size_t *);
> > - int (*set_slave)(struct shdma_chan *, int);
> > + int (*set_slave)(struct shdma_chan *, int, bool);
> > void (*setup_xfer)(struct shdma_chan *, int);
> > void (*start_xfer)(struct shdma_chan *, struct shdma_desc *);
> > struct shdma_desc *(*embedded_desc)(void *, int);
>
>
> --
> ~Vinod
>

---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
http://www.open-technology.de/


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