Messages in this thread | | | Date | Tue, 6 Jul 2010 14:37:19 +0200 | Subject | Re: [PATCH 1/3] DMAENGINE: generic slave channel control | From | Linus Walleij <> |
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Hi Dan,
any thoughts on this? Personally I really like this abstraction from my experience with embedded DMA controllers, but I don't have your wide experience of DMA hardware.
Yours, Linus Walleij
2010/6/29 Linus Walleij <linus.walleij@stericsson.com>: > This adds an interface to the DMAengine to make it possible to > reconfigure a slave channel at runtime. We add a few foreseen > config parameters to the passed struct, with a void * pointer > for custom per-device or per-platform runtime slave data. > > Signed-off-by: Linus Walleij <linus.walleij@stericsson.com> > --- > include/linux/dmaengine.h | 48 +++++++++++++++++++++++++++++++++++++++++++++ > 1 files changed, 48 insertions(+), 0 deletions(-) > > diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h > index 5204f01..e2601bd 100644 > --- a/include/linux/dmaengine.h > +++ b/include/linux/dmaengine.h > @@ -114,11 +114,17 @@ enum dma_ctrl_flags { > * @DMA_TERMINATE_ALL: terminate all ongoing transfers > * @DMA_PAUSE: pause ongoing transfers > * @DMA_RESUME: resume paused transfer > + * @DMA_SLAVE_CONFIG: this command is only implemented by DMA controllers > + * that need to runtime reconfigure the slave channels (as opposed to passing > + * configuration data in statically from the platform). An additional > + * argument of struct dma_slave_config must be passed in with this > + * command. > */ > enum dma_ctrl_cmd { > DMA_TERMINATE_ALL, > DMA_PAUSE, > DMA_RESUME, > + DMA_SLAVE_CONFIG, > }; > > /** > @@ -199,6 +205,48 @@ struct dma_chan_dev { > atomic_t *idr_ref; > }; > > +/** > + * struct dma_slave_config - dma slave channel runtime config > + * @addr: this is the physical address where DMA slave data should be > + * read (RX) or written (TX) > + * @addr_width: this is the width of the source (RX) or target > + * (TX) register where DMA data shall be read/written, in bytes. > + * legal values: 1, 2, 4, 8. > + * @direction: whether the data shall go in or out on this slave > + * channel, right now. > + * @maxburst: the maximum number of words (note: words, as in units > + * of the addr_width member, not bytes) that can be sent in one burst > + * to the device. Typically something like half the FIFO depth on > + * I/O peripherals so you don't overflow it. > + * @private_config: if you need to pass in specialized configuration > + * at runtime, apart from the generic things supported in this > + * struct, you provide it in this pointer and dereference it inside > + * your dmaengine driver to get the proper configuration bits out. > + * > + * This struct is passed in as configuration data to a DMA engine > + * in order to set up a certain channel for DMA transport at runtime. > + * The DMA device/engine has to provide support for an additional > + * command in the channel config interface, DMA_SLAVE_CONFIG > + * and this struct will then be passed in as an argument to the > + * DMA engine device_control() function. > + * > + * The rationale for adding configuration information to this struct > + * is as follows: if it is likely that most DMA slave controllers in > + * the world will support the configuration option, then make it > + * generic. If not, if it is fixed so that it be sent in static from > + * the platform data, then prefer to do that. Else, if it is neither > + * fixed, not generic enough (such as bus mastership on some CPU > + * family and whatnot) then pass it in the private_config member > + * and dereference it to some per-device struct in your driver. > + */ > +struct dma_slave_config { > + dma_addr_t addr; > + u8 addr_width:4; > + enum dma_data_direction direction; > + int maxburst; > + void *private_config; > +}; > + > static inline const char *dma_chan_name(struct dma_chan *chan) > { > return dev_name(&chan->dev->device); > -- > 1.7.0.1 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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