[PATCH V2 03/14] i3c: mipi-i3c-hci: Factor out DMA mapping from queuing path

[Frank Li]

On Wed, Mar 04, 2026 at 08:16:54PM +0200, Adrian Hunter wrote:
> Prepare for fixing a race in the DMA ring enqueue path when handling
> parallel transfers.  Move all DMA mapping out of hci_dma_queue_xfer()
> and into a new helper that performs the mapping up front.
>
> This refactoring allows the upcoming fix to extend the spinlock coverage
> around the enqueue operation without performing DMA mapping under the
> spinlock.
>
> No functional change is intended in this patch.
>
> Fixes: 9ad9a52cce282 ("i3c/master: introduce the mipi-i3c-hci driver")
> Cc: stable at vger.kernel.org
> Signed-off-by: Adrian Hunter <adrian.hunter at intel.com>
> ---

Reviewed-by: Frank Li <Frank.Li at nxp.com>
>
>
> Changes in V2:
>
> 	New patch split out from "i3c: mipi-i3c-hci: Fix race in DMA ring
> 	enqueue for parallel xfers"
>
>
>  drivers/i3c/master/mipi-i3c-hci/dma.c | 49 ++++++++++++++++++---------
>  1 file changed, 33 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/i3c/master/mipi-i3c-hci/dma.c b/drivers/i3c/master/mipi-i3c-hci/dma.c
> index b903a2da1fd1..ba451f026386 100644
> --- a/drivers/i3c/master/mipi-i3c-hci/dma.c
> +++ b/drivers/i3c/master/mipi-i3c-hci/dma.c
> @@ -439,6 +439,33 @@ static void hci_dma_unmap_xfer(struct i3c_hci *hci,
>  	}
>  }
>
> +static struct i3c_dma *hci_dma_map_xfer(struct device *dev, struct hci_xfer *xfer)
> +{
> +	enum dma_data_direction dir = xfer->rnw ? DMA_FROM_DEVICE : DMA_TO_DEVICE;
> +	bool need_bounce = device_iommu_mapped(dev) && xfer->rnw && (xfer->data_len & 3);
> +
> +	return i3c_master_dma_map_single(dev, xfer->data, xfer->data_len, need_bounce, dir);
> +}
> +
> +static int hci_dma_map_xfer_list(struct i3c_hci *hci, struct device *dev,
> +				 struct hci_xfer *xfer_list, int n)
> +{
> +	for (int i = 0; i < n; i++) {
> +		struct hci_xfer *xfer = xfer_list + i;
> +
> +		if (!xfer->data)
> +			continue;
> +
> +		xfer->dma = hci_dma_map_xfer(dev, xfer);
> +		if (!xfer->dma) {
> +			hci_dma_unmap_xfer(hci, xfer_list, i);
> +			return -ENOMEM;
> +		}
> +	}
> +
> +	return 0;
> +}
> +
>  static int hci_dma_queue_xfer(struct i3c_hci *hci,
>  			      struct hci_xfer *xfer_list, int n)
>  {
> @@ -446,6 +473,11 @@ static int hci_dma_queue_xfer(struct i3c_hci *hci,
>  	struct hci_rh_data *rh;
>  	unsigned int i, ring, enqueue_ptr;
>  	u32 op1_val, op2_val;
> +	int ret;
> +
> +	ret = hci_dma_map_xfer_list(hci, rings->sysdev, xfer_list, n);
> +	if (ret)
> +		return ret;
>
>  	/* For now we only use ring 0 */
>  	ring = 0;
> @@ -456,9 +488,6 @@ static int hci_dma_queue_xfer(struct i3c_hci *hci,
>  	for (i = 0; i < n; i++) {
>  		struct hci_xfer *xfer = xfer_list + i;
>  		u32 *ring_data = rh->xfer + rh->xfer_struct_sz * enqueue_ptr;
> -		enum dma_data_direction dir = xfer->rnw ? DMA_FROM_DEVICE :
> -							  DMA_TO_DEVICE;
> -		bool need_bounce;
>
>  		/* store cmd descriptor */
>  		*ring_data++ = xfer->cmd_desc[0];
> @@ -477,18 +506,6 @@ static int hci_dma_queue_xfer(struct i3c_hci *hci,
>
>  		/* 2nd and 3rd words of Data Buffer Descriptor Structure */
>  		if (xfer->data) {
> -			need_bounce = device_iommu_mapped(rings->sysdev) &&
> -				      xfer->rnw &&
> -				      xfer->data_len != ALIGN(xfer->data_len, 4);
> -			xfer->dma = i3c_master_dma_map_single(rings->sysdev,
> -							      xfer->data,
> -							      xfer->data_len,
> -							      need_bounce,
> -							      dir);
> -			if (!xfer->dma) {
> -				hci_dma_unmap_xfer(hci, xfer_list, i);
> -				return -ENOMEM;
> -			}
>  			*ring_data++ = lower_32_bits(xfer->dma->addr);
>  			*ring_data++ = upper_32_bits(xfer->dma->addr);
>  		} else {
> @@ -511,7 +528,7 @@ static int hci_dma_queue_xfer(struct i3c_hci *hci,
>  		op2_val = rh_reg_read(RING_OPERATION2);
>  		if (enqueue_ptr == FIELD_GET(RING_OP2_CR_DEQ_PTR, op2_val)) {
>  			/* the ring is full */
> -			hci_dma_unmap_xfer(hci, xfer_list, i + 1);
> +			hci_dma_unmap_xfer(hci, xfer_list, n);
>  			return -EBUSY;
>  		}
>  	}
> --
> 2.51.0
>
>
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