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



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