linux-kernel - Re: [PATCH 1/3] DMAENGINE: generic slave channel control

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Date:	Mon, 19 Jul 2010 14:36:16 -0700
From:	Dan Williams <dan.j.williams@...el.com>
To:	Linus Walleij <linus.ml.walleij@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	Linus Walleij <linus.walleij@...ricsson.com>,
	vinod.koul@...el.com
Subject: Re: [PATCH 1/3] DMAENGINE: generic slave channel control

On Wed, Jul 14, 2010 at 4:11 PM, Linus Walleij
<linus.ml.walleij@...il.com> wrote:
> Ping on this subject, I have the PL08x driver depending on this
> so if it's not OK I have to rewrite that patch soonish.
>
> Also the DMA for PrimeCells use it so I would like to respin that
> patch series using this generic control if it is accepted.
>
> As mentions something like this will be needed for us anyway,
> so in case it's not OK I'll likely go for more or less the same
> struct, just that it is for DMA40 and its clients solely, then on
> top of that a PrimeCell interface more or less redefining the
> same things again or wrapping it.
>

I think it looks ok, I just want to get one other dmaslave driver
author to nod that dma_slave_config has the right amount of fields.  I
initially put too much into dma_async_tx_descriptor.  I'll take this
as is if we don't get feedback, but that would remove my hesitation.

The recently submitted intel_mid driver [1] seems to have a similar structure:

+/**
+ * struct intel_mid_dma_slave - DMA slave structure
+ *
+ * @dma_dev: DMA master client
+ * @tx_reg: physical address of data register used for
+ *     memory-to-peripheral transfers
+ * @rx_reg: physical address of data register used for
+ *     peripheral-to-memory transfers
+ * @tx_width: tx register width
+ * @rx_width: rx register width
+ * @dirn: DMA trf direction
+
+ * @cfg_hi: Platform-specific initializer for the CFG_HI register
+ * @cfg_lo: Platform-specific initializer for the CFG_LO register
+
+ * @ tx_width: width of src and dstn
+ * @ hs_mode: SW or HW handskaking mode
+ * @ cfg_mode: Mode configuration, DMA mem to mem to dev & mem
+ */
+struct intel_mid_dma_slave {
+       enum dma_data_direction         dirn;
+       enum intel_mid_dma_width        src_width; /*width of DMA src txn*/
+       enum intel_mid_dma_width        dst_width; /*width of DMA dst txn*/
+       enum intel_mid_dma_hs_mode      hs_mode;  /*handshaking*/
+       enum intel_mid_dma_mode         cfg_mode; /*mode configuration*/
+       enum intel_mid_dma_msize        src_msize; /*size if src burst*/
+       enum intel_mid_dma_msize        dst_msize; /*size of dst burst*/
+       dma_async_tx_callback           callback; /*callback function*/
+       void                            *callback_param; /*param for callback*/
+       unsigned int            device_instance; /*0, 1 for periphral instance*/
+};
+

Vinod, would you consider switching to dma_slave_config [2] for this
information, or at a minimum wrapping dma_slave_config with your
intel_mid specific fields?

--
Dan

[1]: http://marc.info/?l=linux-kernel&m=127687775404278&w=2
[2]: http://marc.info/?l=linux-kernel&m=127777055428648&w=2
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