Re: [PATCH v4 24/25] dmaengine: sdxi: MSI/MSI-X vector allocation and mapping

[Frank Li <Frank.li@oss.nxp.com>]

On Tue, Nov 03, 2026 at 08:50:05PM -0600, Nathan Lynch wrote:
> Request MSI/MSI-X vectors for the error log interrupt and up to one
> interrupt per supported client context. Reserve vector 0 for the error log
> and track the remaining allocated vectors with an IDA.
>
> Introduce sdxi_alloc_vector() and sdxi_free_vector() which are thin
> wrappers around the IDA that tracks the allocated vector range.
>
> Introduce sdxi_vector_to_irq() which invokes a new get_irq() bus op to
> translate the device-relative index to the Linux IRQ number for use
> with request_irq() etc. For PCI this dispatches to pci_irq_vector().
>
> Co-developed-by: Wei Huang <wei.huang2@amd.com>
> Signed-off-by: Wei Huang <wei.huang2@amd.com>
> Signed-off-by: Nathan Lynch <nathan.lynch@amd.com>
> ---

Reviewed-by: Frank Li <Frank.Li@nxp.com>

>  drivers/dma/sdxi/device.c |  3 +++
>  drivers/dma/sdxi/pci.c    | 30 ++++++++++++++++++++++++++-
>  drivers/dma/sdxi/sdxi.h   | 53 +++++++++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 85 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/dma/sdxi/device.c b/drivers/dma/sdxi/device.c
> index 8786be71d3e3..30c4e687cedf 100644
> --- a/drivers/dma/sdxi/device.c
> +++ b/drivers/dma/sdxi/device.c
> @@ -11,6 +11,7 @@
>  #include <linux/dma-mapping.h>
>  #include <linux/dmapool.h>
>  #include <linux/export.h>
> +#include <linux/idr.h>
>  #include <linux/iopoll.h>
>  #include <linux/jiffies.h>
>  #include <linux/limits.h>
> @@ -437,6 +438,7 @@ int sdxi_register(struct device *dev, const struct sdxi_bus_ops *ops)
>
>  	sdxi->dev = dev;
>  	sdxi->bus_ops = ops;
> +	ida_init(&sdxi->vectors);
>  	xa_init_flags(&sdxi->client_cxts, XA_FLAGS_ALLOC1);
>  	dev_set_drvdata(dev, sdxi);
>
> @@ -459,6 +461,7 @@ void sdxi_unregister(struct device *dev)
>  	/* Stop/reset is best effort if the hardware cannot be quiesced. */
>  	sdxi_dev_stop(sdxi);
>  	sdxi_client_cxts_exit(sdxi);
> +	ida_destroy(&sdxi->vectors);
>  }
>  EXPORT_SYMBOL_NS_GPL(sdxi_unregister, "SDXI");
>
> diff --git a/drivers/dma/sdxi/pci.c b/drivers/dma/sdxi/pci.c
> index d196ab5cf6f1..ef978ca22db1 100644
> --- a/drivers/dma/sdxi/pci.c
> +++ b/drivers/dma/sdxi/pci.c
> @@ -31,8 +31,9 @@ static int sdxi_pci_init(struct sdxi_dev *sdxi)
>  {
>  	struct pci_dev *pdev = sdxi_to_pci_dev(sdxi);
>  	struct device *dev = &pdev->dev;
> +	u32 cap1_max_cxt;
>  	u64 cap1;
> -	int ret;
> +	int vecs, ret;
>
>  	ret = pcim_enable_device(pdev);
>  	if (ret)
> @@ -63,6 +64,27 @@ static int sdxi_pci_init(struct sdxi_dev *sdxi)
>  	sdxi->has_mailbox = pdev->is_virtfn ||
>  		pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_SRIOV);
>
> +	/*
> +	 * Allocate the minimum required set of vectors plus one for
> +	 * each client context supported by the function.
> +	 *
> +	 * pci_alloc_irq_vectors() handles calling pci_free_irq_vectors()
> +	 * automatically despite not being called pcim_*. See
> +	 * pci_setup_msi_context().
> +	 */
> +	cap1_max_cxt = FIELD_GET(SDXI_MMIO_CAP1_MAX_CXT,
> +				 sdxi_read64(sdxi, SDXI_MMIO_CAP1));
> +	vecs = pci_alloc_irq_vectors(pdev, SDXI_MIN_VECTORS,
> +				     SDXI_MIN_VECTORS + cap1_max_cxt,
> +				     PCI_IRQ_MSI | PCI_IRQ_MSIX);
> +	if (vecs < 0)
> +		return dev_err_probe(dev, vecs,
> +				     "failed to allocate MSIs (max_cxt=%u)\n",
> +				     cap1_max_cxt);
> +
> +	sdxi->nr_vectors = vecs;
> +	dev_dbg(sdxi->dev, "allocated %u vectors\n", sdxi->nr_vectors);
> +
>  	pci_set_master(pdev);
>  	return 0;
>  }
> @@ -86,9 +108,15 @@ static int sdxi_pci_reset(struct sdxi_dev *sdxi)
>  	return err;
>  }
>
> +static int sdxi_pci_get_irq(struct sdxi_dev *sdxi, unsigned int nr)
> +{
> +	return pci_irq_vector(sdxi_to_pci_dev(sdxi), nr);
> +}
> +
>  static const struct sdxi_bus_ops sdxi_pci_ops = {
>  	.init = sdxi_pci_init,
>  	.reset = sdxi_pci_reset,
> +	.get_irq = sdxi_pci_get_irq,
>  };
>
>  static int sdxi_pci_probe(struct pci_dev *pdev,
> diff --git a/drivers/dma/sdxi/sdxi.h b/drivers/dma/sdxi/sdxi.h
> index aaa43eab00b3..07044d837d9a 100644
> --- a/drivers/dma/sdxi/sdxi.h
> +++ b/drivers/dma/sdxi/sdxi.h
> @@ -8,8 +8,10 @@
>  #ifndef DMA_SDXI_H
>  #define DMA_SDXI_H
>
> +#include <linux/bug.h>
>  #include <linux/compiler_types.h>
>  #include <linux/dev_printk.h>
> +#include <linux/idr.h>
>  #include <linux/io.h>
>  #include <linux/types.h>
>  #include <linux/xarray.h>
> @@ -25,6 +27,18 @@
>  #define L1_CXT_CTRL_PTR_SHIFT		6
>  #define L1_CXT_AKEY_PTR_SHIFT		12
>
> +enum {
> +	/* Reserve vector 0 for the error log interrupt. */
> +	SDXI_ERROR_VECTOR = 0,
> +
> +	/*
> +	 * Request at least one vector to account for the error log
> +	 * interrupt. Increment this if the driver gains more
> +	 * dedicated interrupts (e.g. one for the admin context).
> +	 */
> +	SDXI_MIN_VECTORS = 1,
> +};
> +
>  struct sdxi_dev;
>
>  /**
> @@ -41,6 +55,10 @@ struct sdxi_bus_ops {
>  	 * @reset: Bus-specific recovery when the native stop sequence fails.
>  	 */
>  	int (*reset)(struct sdxi_dev *sdxi);
> +	/**
> +	 * @get_irq: Map device interrupt index to Linux IRQ number.
> +	 */
> +	int (*get_irq)(struct sdxi_dev *sdxi, unsigned int index);
>  };
>
>  struct sdxi_dev {
> @@ -61,6 +79,9 @@ struct sdxi_dev {
>
>  	struct dma_pool *cxt_ctl_pool;
>
> +	unsigned int nr_vectors;
> +	struct ida vectors;
> +
>  	struct sdxi_cxt *admin_cxt;
>  	struct xarray client_cxts; /* context id -> (struct sdxi_cxt *) */
>
> @@ -69,6 +90,38 @@ struct sdxi_dev {
>  	const struct sdxi_bus_ops *bus_ops;
>  };
>
> +/**
> + * sdxi_alloc_vector() - Allocate an interrupt vector.
> + *
> + * A vector that will have the same lifetime as the device does not
> + * need to be released explicitly. Otherwise the vector must be
> + * released with sdxi_free_vector().
> + */
> +static inline int sdxi_alloc_vector(struct sdxi_dev *sdxi)
> +{
> +	return ida_alloc_range(&sdxi->vectors, SDXI_MIN_VECTORS,
> +			       sdxi->nr_vectors - 1, GFP_KERNEL);
> +}
> +
> +/**
> + * sdxi_free_vector() - Release a previously allocated index.
> + */
> +static inline void sdxi_free_vector(struct sdxi_dev *sdxi, unsigned int nr)
> +{
> +	ida_free(&sdxi->vectors, nr);
> +}
> +
> +/**
> + * sdxi_vector_to_irq() - Translate an allocated interrupt vector to
> + *                        Linux IRQ number suitable for passing to
> + *                        request_irq() et al.
> + */
> +static inline int sdxi_vector_to_irq(struct sdxi_dev *sdxi, unsigned int nr)
> +{
> +	WARN_ON_ONCE(!ida_exists(&sdxi->vectors, nr));
> +	return sdxi->bus_ops->get_irq(sdxi, nr);
> +}
> +
>  int sdxi_register(struct device *dev, const struct sdxi_bus_ops *ops);
>  void sdxi_unregister(struct device *dev);
>
>
> --
> 2.56.0
>