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Date: Wed, 15 May 2013 15:39:09 +0200
From: Lars-Peter Clausen <lars@...afoo.de>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>
CC: linux-kernel@...r.kernel.org, Vinod Koul <vinod.koul@...el.com>,
Dan Williams <djbw@...com>,
Russell King <rmk+kernel@....linux.org.uk>,
Peter Ujfalusi <peter.ujfalusi@...com>
Subject: Re: [RFC/PATCH] dma: of: Make of_dma_simple_xlate match on DMA device
and channel ID
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 <laurent.pinchart@...asonboard.com>
Hi,
I've submitted a very similar patch some time ago, see
https://lkml.org/lkml/2013/3/25/250
- Lars
> ---
> 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)
--
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