Subject: [RFC/PATCH] dma: of: Make of_dma_simple_xlate match on DMA device and channel ID

From: [email-masked] (Laurent Pinchart)
Date: Thu, 16 May 2013 13:30:25 +0200

Hi Lars-Peter,

On Wednesday 15 May 2013 16:52:03 Lars-Peter Clausen wrote:
> On 05/15/2013 03:55 PM, Laurent Pinchart wrote:
> > On Wednesday 15 May 2013 15:39:09 Lars-Peter Clausen wrote:
> >> On 05/15/2013 03:27 PM, Laurent Pinchart wrote:
> >>> When translating a DT DMA channel specifier, the most common use case is
> >>> to match the DMA channel based on the channel DMA engine and channel ID.
> >>> Modify the of_dma_simple_xlate() function to do so, simplifying the API
> >>> for DMA engine drivers.
> >>> 
> >>> There is no need to check the DMA cells count in the filter function as
> >>> the check is already performed by the caller in of_dma_get_controller().
> >>> 
> >>> Signed-off-by: Laurent Pinchart <[email-masked]>
> >> 
> >> Hi,
> >> 
> >> I've submitted a very similar patch some time ago, see
> >> https://lkml.org/lkml/2013/3/25/250
> > 
> > Thanks. So my patch makes at least some sense :-)
> > 
> > I had the impression that this is what omap-dma needs as well, hence the
> > modification to the existing xlate function. I'm fine with a separate
> > function as well if the current code covers different use cases.
> 
> My first attempt was to modify simple_xlate function, but I think it didn't
> work for all users (some of which aren't applied yet), so I added a separate
> function.

OK. Do you plan to push your patch to mainline ? You can add my

Tested-by: Laurent Pinchart <[email-masked]>
Acked-by: Laurent Pinchart <[email-masked]>

> >>> ---
> >>> 
> >>>  drivers/dma/of-dma.c   | 39 +++++++++++++++++++++++++++++++--------
> >>>  drivers/dma/omap-dma.c |  8 +-------
> >>>  include/linux/of_dma.h |  5 -----
> >>>  3 files changed, 32 insertions(+), 20 deletions(-)
> >>> 
> >>> I've implemented this function while working on a DMA engine driver, and
> >>> realized that it wasn't specific to my driver at all. As I'm new to the
> >>> DMA engine API, I'd appreciate feedback on whether this change makes
> >>> sense, or if I should instead keep the existing of_dma_simple_xlate()
> >>> function and create a separate simple xlate helper.
> >>> 
> >>> diff --git a/drivers/dma/of-dma.c b/drivers/dma/of-dma.c
> >>> index 7aa0864..702a45d 100644
> >>> --- a/drivers/dma/of-dma.c
> >>> +++ b/drivers/dma/of-dma.c
> >>> @@ -202,6 +202,27 @@ struct dma_chan
> >>> *of_dma_request_slave_channel(struct
> >>> device_node *np,
> >>> 
> >>>  	return NULL;
> >>>  
> >>>  }
> >>> 
> >>> +struct of_dma_filter_args {
> >>> +	struct dma_device *device;
> >>> +	unsigned int chan_id;
> >>> +};
> >>> +
> >>> +/**
> >>> + * of_dma_simple_xlate_filter - Channel filter function for
> >>> of_dma_simple_xlate + * @dma_chan:	pointer to candidate DMA channel
> >>> + * @param:	pointer to filter parameter
> >>> + *
> >>> + * Filter out candidate DMA channels that don't match the channel ID or
> >>> + * DMA engine device passed as arguments.
> >>> + */
> >>> +static bool of_dma_simple_xlate_filter(struct dma_chan *chan, void
> >>> *param)
> >>> +{
> >>> +	struct of_dma_filter_args *fargs = param;
> >>> +
> >>> +	return (chan->device == fargs->device) &&
> >>> +	       (chan->chan_id == fargs->chan_id);
> >>> +}
> >>> +
> >>> 
> >>>  /**
> >>>  
> >>>   * of_dma_simple_xlate - Simple DMA engine translation function
> >>>   * @dma_spec:	pointer to DMA specifier as found in the device tree
> >>> 
> >>> @@ -216,16 +237,18 @@ struct dma_chan
> >>> *of_dma_request_slave_channel(struct
> >>> device_node *np,>
> >>> 
> >>>  struct dma_chan *of_dma_simple_xlate(struct of_phandle_args *dma_spec,
> >>>  
> >>>  						struct of_dma *ofdma)
> >>>  
> >>>  {
> >>> 
> >>> -	int count = dma_spec->args_count;
> >>> -	struct of_dma_filter_info *info = ofdma->of_dma_data;
> >>> +	struct dma_device *dev = ofdma->of_dma_data;
> >>> +	struct of_dma_filter_args fargs;
> >>> +	dma_cap_mask_t cap;
> >>> 
> >>> -	if (!info || !info->filter_fn)
> >>> -		return NULL;
> >>> +	/* There's no need to specify matching caps as we're going to match a
> >>> +	 * specific DMA channel anyway.
> >>> +	 */
> >>> +	dma_cap_zero(cap);
> >>> 
> >>> -	if (count != 1)
> >>> -		return NULL;
> >>> +	fargs.device = dev;
> >>> +	fargs.chan_id = dma_spec->args[0];
> >>> 
> >>> -	return dma_request_channel(info->dma_cap, info->filter_fn,
> >>> -			&dma_spec->args[0]);
> >>> +	return dma_request_channel(cap, of_dma_simple_xlate_filter, &fargs);
> >>> 
> >>>  }
> >>>  EXPORT_SYMBOL_GPL(of_dma_simple_xlate);
> >>> 
> >>> diff --git a/drivers/dma/omap-dma.c b/drivers/dma/omap-dma.c
> >>> index ec3fc4f..7e7ff06 100644
> >>> --- a/drivers/dma/omap-dma.c
> >>> +++ b/drivers/dma/omap-dma.c
> >>> @@ -69,10 +69,6 @@ static const unsigned es_bytes[] = {
> >>> 
> >>>  	[OMAP_DMA_DATA_TYPE_S32] = 4,
> >>>  
> >>>  };
> >>> 
> >>> -static struct of_dma_filter_info omap_dma_info = {
> >>> -	.filter_fn = omap_dma_filter_fn,
> >>> -};
> >>> -
> >>> 
> >>>  static inline struct omap_dmadev *to_omap_dma_dev(struct dma_device *d)
> >>>  {
> >>>  
> >>>  	return container_of(d, struct omap_dmadev, ddev);
> >>> 
> >>> @@ -641,11 +637,9 @@ static int omap_dma_probe(struct platform_device
> >>> *pdev)>
> >>> 
> >>>  	platform_set_drvdata(pdev, od);
> >>>  	if (pdev->dev.of_node) {
> >>> 
> >>> -		omap_dma_info.dma_cap = od->ddev.cap_mask;
> >>> -
> >>> 
> >>>  		/* Device-tree DMA controller registration */
> >>>  		rc = of_dma_controller_register(pdev->dev.of_node,
> >>> 
> >>> -				of_dma_simple_xlate, &omap_dma_info);
> >>> +				of_dma_simple_xlate, &od->ddev);
> >>> 
> >>>  		if (rc) {
> >>>  		
> >>>  			pr_warn("OMAP-DMA: failed to register DMA controller\n");
> >>>  			dma_async_device_unregister(&od->ddev);
> >>> 
> >>> diff --git a/include/linux/of_dma.h b/include/linux/of_dma.h
> >>> index 364dda7..3c0d9ac 100644
> >>> --- a/include/linux/of_dma.h
> >>> +++ b/include/linux/of_dma.h
> >>> @@ -27,11 +27,6 @@ struct of_dma {
> >>> 
> >>>  	void			*of_dma_data;
> >>>  
> >>>  };
> >>> 
> >>> -struct of_dma_filter_info {
> >>> -	dma_cap_mask_t	dma_cap;
> >>> -	dma_filter_fn	filter_fn;
> >>> -};
> >>> -
> >>> 
> >>>  #ifdef CONFIG_OF
> >>>  extern int of_dma_controller_register(struct device_node *np,
> >>>  
> >>>  		struct dma_chan *(*of_dma_xlate)
-- 
Regards,

Laurent Pinchart