Re: [PATCH 2/2] dmaengine: fsl-edma: add per-channel IOMMU support via iommu-map

[Frank Li]

On Wed, Sep 16, 2026 at 11:55:26PM +0800, Peng Fan (OSS) wrote:
> From: Peng Fan <peng.fan@xxxxxxx>
>
> Add iommu-map support so that each eDMA channel can be individually
> mapped to an IOMMU stream ID.
>
> At probe time, fsl_edma_init_chan_iommu() prepares per-channel devices
> by initializing DMA masks and bus pointers so of_dma_configure_id()
> can be called later.
>
> At xlate time, fsl_edma_chan_configure_iommu() looks up the allocated
> channel index in iommu-map. If an entry exists, it calls
> of_dma_configure_id() to attach the IOMMU domain and sets chan_dma_dev
> so dmaengine_get_dma_device() returns the per-channel device.
> Channels without a matching entry operate in bypass mode.
>
> Also switch fsl_edma_prep_slave_dma() and fsl_edma_unprep_slave_dma()
> to use dmaengine_get_dma_device() for DMA resource mapping.
>
> Assisted-by: Claude:claude-opus-4-6
> Signed-off-by: Peng Fan <peng.fan@xxxxxxx>
> ---
>  drivers/dma/fsl-edma-common.c |  6 ++--
>  drivers/dma/fsl-edma-common.h |  1 +
>  drivers/dma/fsl-edma-main.c   | 76 ++++++++++++++++++++++++++++++++++++++++++-
>  3 files changed, 80 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/dma/fsl-edma-common.c b/drivers/dma/fsl-edma-common.c
> index bb7531c456dfa..58a92ff4ddbe7 100644
> --- a/drivers/dma/fsl-edma-common.c
> +++ b/drivers/dma/fsl-edma-common.c
> @@ -283,8 +283,10 @@ int fsl_edma_resume(struct dma_chan *chan)
>
>  static void fsl_edma_unprep_slave_dma(struct fsl_edma_chan *fsl_chan)
>  {
> +	struct device *dev = dmaengine_get_dma_device(&fsl_chan->vchan.chan);
> +
>  	if (fsl_chan->dma_dir != DMA_NONE)
> -		dma_unmap_resource(fsl_chan->vchan.chan.device->dev,
> +		dma_unmap_resource(dev,
>  				   fsl_chan->dma_dev_addr,
>  				   fsl_chan->dma_dev_size,
>  				   fsl_chan->dma_dir, 0);
> @@ -294,7 +296,7 @@ static void fsl_edma_unprep_slave_dma(struct fsl_edma_chan *fsl_chan)
>  static bool fsl_edma_prep_slave_dma(struct fsl_edma_chan *fsl_chan,
>  				    enum dma_transfer_direction dir)
>  {
> -	struct device *dev = fsl_chan->vchan.chan.device->dev;
> +	struct device *dev = dmaengine_get_dma_device(&fsl_chan->vchan.chan);
>  	enum dma_data_direction dma_dir;
>  	phys_addr_t addr = 0;
>  	u32 size = 0;
> diff --git a/drivers/dma/fsl-edma-common.h b/drivers/dma/fsl-edma-common.h
> index 205a964890948..85487763e05ab 100644
> --- a/drivers/dma/fsl-edma-common.h
> +++ b/drivers/dma/fsl-edma-common.h
> @@ -264,6 +264,7 @@ struct fsl_edma_engine {
>  	int			txirq_16_31;
>  	int			errirq;
>  	bool			big_endian;
> +	bool			has_iommu_map;
>  	struct edma_regs	regs;
>  	u64			chan_masked;
>  	struct fsl_edma_chan	chans[] __counted_by(n_chans);
> diff --git a/drivers/dma/fsl-edma-main.c b/drivers/dma/fsl-edma-main.c
> index d9fb717b5b53c..eabb0086fc9de 100644
> --- a/drivers/dma/fsl-edma-main.c
> +++ b/drivers/dma/fsl-edma-main.c
> @@ -16,6 +16,7 @@
>  #include <linux/interrupt.h>
>  #include <linux/clk.h>
>  #include <linux/of.h>
> +#include <linux/of_device.h>
>  #include <linux/of_dma.h>
>  #include <linux/dma-mapping.h>
>  #include <linux/pm_runtime.h>
> @@ -24,6 +25,7 @@
>
>  #include "fsl-edma-common.h"
>
> +static int fsl_edma_chan_configure_iommu(struct fsl_edma_chan *fsl_chan);

is possible move function here to avoid forware declear?

>  static void fsl_edma_synchronize(struct dma_chan *chan)
>  {
>  	struct fsl_edma_chan *fsl_chan = to_fsl_edma_chan(chan);
> @@ -298,7 +300,7 @@ static struct dma_chan *fsl_edma3_xlate(struct of_phandle_args *dma_spec,
>  	struct dma_chan *chan, *_chan;
>  	struct fsl_edma_chan *fsl_chan;
>  	bool b_chmux;
> -	int i;
> +	int i, ret;
>
>  	if (dma_spec->args_count != 3)
>  		return NULL;
> @@ -332,6 +334,12 @@ static struct dma_chan *fsl_edma3_xlate(struct of_phandle_args *dma_spec,
>  		fsl_chan->is_remote = dma_spec->args[2] & FSL_EDMA_REMOTE;
>  		fsl_chan->is_multi_fifo = dma_spec->args[2] & FSL_EDMA_MULTI_FIFO;
>
> +		if (fsl_edma->has_iommu_map) {

should has_iommu_map be per channel? How about some channel use iommu
but some not?

> +			ret = fsl_edma_chan_configure_iommu(fsl_chan);
> +			if (ret)
> +				return NULL;
> +		}
> +
>  		chan = dma_get_slave_channel(chan);
>  		chan->device->privatecnt++;
>  		return chan;
> @@ -695,6 +703,70 @@ static int fsl_edma3_attach_pd(struct platform_device *pdev, struct fsl_edma_eng
>  	return -EINVAL;
>  }
>
> +/**
> + * fsl_edma_init_chan_iommu - prepare per-channel devices for IOMMU
> + * @pdev: the eDMA platform device
> + * @fsl_edma: the eDMA engine instance
> + *
> + * Must be called after dmaenginem_async_device_register() so that each
> + * channel's chan->dev->device is already registered.
> + *
> + * Initialize DMA mask and bus on each channel device so that
> + * of_dma_configure_id() can be called later at xlate time.
> + */
> +static void fsl_edma_init_chan_iommu(struct platform_device *pdev,
> +				    struct fsl_edma_engine *fsl_edma)
> +{
> +	int i;
> +
> +	if (!of_property_present(pdev->dev.of_node, "iommu-map"))
> +		return;
> +
> +	for (i = 0; i < fsl_edma->n_chans; i++) {
> +		struct fsl_edma_chan *fsl_chan = &fsl_edma->chans[i];
> +		struct device *dev;
> +
> +		if (fsl_edma->chan_masked & BIT(i))
> +			continue;
> +
> +		dev = &fsl_chan->vchan.chan.dev->device;

use new API vchan_chan_dev()

> +		dev->coherent_dma_mask = pdev->dev.coherent_dma_mask;
> +		dev->dma_mask = &dev->coherent_dma_mask;
> +		dev->bus = pdev->dev.bus;

I think these information should be set even without iommu.

> +	}
> +
> +	fsl_edma->has_iommu_map = true;
> +}
> +
> +static int fsl_edma_chan_configure_iommu(struct fsl_edma_chan *fsl_chan)
> +{
> +	struct device *dev = &fsl_chan->vchan.chan.dev->device;

use new API vchan_chan_dev()

> +	struct device_node *np = fsl_chan->edma->dma_dev.dev->of_node;
> +	struct of_phandle_args iommu_spec = {};
> +	u32 chan_id = fsl_chan - fsl_chan->edma->chans;
> +	int ret;
> +
> +	if (fsl_chan->vchan.chan.dev->chan_dma_dev)
> +		return 0;
> +
> +	ret = of_map_iommu_id(np, chan_id, &iommu_spec);
> +	if (ret || !iommu_spec.np)
> +		return 0;
> +	of_node_put(iommu_spec.np);
> +
> +	ret = of_dma_configure_id(dev, np, true, &chan_id);
> +	if (ret) {
> +		dev_err(dev, "DMA configure failed for ch%u: %d\n",
> +			chan_id, ret);

use dev_err_probe() to avoid print error when defer probe

Frank
> +		return ret;
> +	}
> +
> +	fsl_chan->vchan.chan.dev->chan_dma_dev = true;
> +	dev_dbg(dev, "ch%u: IOMMU domain configured\n", chan_id);
> +
> +	return 0;
> +}
> +
>  static int fsl_edma_probe(struct platform_device *pdev)
>  {
>  	struct device_node *np = pdev->dev.of_node;
> @@ -882,6 +954,8 @@ static int fsl_edma_probe(struct platform_device *pdev)
>  		return dev_err_probe(&pdev->dev, ret,
>  				     "Can't register Freescale eDMA engine.\n");
>
> +	fsl_edma_init_chan_iommu(pdev, fsl_edma);
> +
>  	ret = devm_of_dma_controller_register(&pdev->dev, np,
>  			drvdata->dmamuxs ? fsl_edma_xlate : fsl_edma3_xlate,
>  			fsl_edma);
>
> --
> 2.34.1
>