[PATCH 1/5] ARM: define the PrimeCell DMA API

[Dan Williams]

[ catching up on the patch backlog ]

On Mon, Mar 8, 2010 at 6:52 AM, Linus Walleij
<linus.walleij at stericsson.com> wrote:
> This patch extends the DMA engine with a PrimeCell superset with
> three functions: configure DMA channel, stop channel, and one for
> getting the number of bytes pending on a channel. These have been
> identified as the basic extensions needed to drive DMA on top of
> the PL011 and PL180 PrimeCells.
>
> Signed-off-by: Linus Walleij <linus.walleij at stericsson.com>
> ---
>  include/linux/amba/dma.h |   44 ++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 44 insertions(+), 0 deletions(-)
>  create mode 100644 include/linux/amba/dma.h
>
> diff --git a/include/linux/amba/dma.h b/include/linux/amba/dma.h
> new file mode 100644
> index 0000000..13196af
> --- /dev/null
> +++ b/include/linux/amba/dma.h
> @@ -0,0 +1,44 @@
> +/*
> + *  linux/include/amba/dma.h
> + *
> + *  Copyright (C) 2010 ST-Ericsson AB
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +#if !defined(AMBA_DMA_H) && defined(CONFIG_DMADEVICES)
> +#define AMBA_DMA_H
> +
> +/**
> + * struct amba_dma_channel_request - this struct is passed in as
> + * configuration data to a DMA engine in order to set up a certain
> + * channel for DMA transport. Anything the DMA engine needs to
> + * know about the PrimeCell shall be passed through this struct.
> + * The DMA engine has to provide an additional function:
> + * dma_set_ambaconfig() in order for it to work with PrimeCells.
> + * @addr: this is the physical address where DMA 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.
> + */
> +struct amba_dma_channel_config {
> +       dma_addr_t addr;
> +       u8 addr_width:4;
> +};
> +
> +/*
> + * The following are extensions to the DMA engine framework
> + * that are needed to use the engine with PrimeCells. We need
> + * to configure devices and be able to stop transfers and
> + * retrieve the number of bytes left on the channel for some
> + * RX transfers when we don't know where and how the transfer
> + * will occur.
> + */
> +void dma_set_ambaconfig(struct dma_chan *chan,
> +                       struct amba_dma_channel_config *config);
> +void dma_stop_channel(struct dma_chan *chan);
> +u32 dma_get_channel_bytes_left(struct dma_chan *chan);

I question if these last two can be generically promoted to dmaengine?
 I already discussed a potential dma_get_channel_bytes() synonym with
Guennadi [1] (wrap ->device_is_tx_complete()), and dma_stop_channel()
looks like it could wrap ->device_terminate_all().

Thoughts?

--
Dan

[1]: http://marc.info/?l=linux-kernel&m=126324913710421&w=2