Re: [PATCH v4 11/25] dmaengine: sdxi: Start functions on probe, stop on remove

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

On Tue, Nov 03, 2026 at 08:49:52PM -0600, Nathan Lynch wrote:
> Activate the function after administrative context setup, polling for
> GSV_ACTIVE or GSV_ERROR with a one-second timeout. Stop the function during
> PCI removal.
>
> 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>
> ---
>  drivers/dma/sdxi/device.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++-
>  drivers/dma/sdxi/pci.c    |  1 +
>  drivers/dma/sdxi/sdxi.h   |  1 +
>  3 files changed, 54 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/dma/sdxi/device.c b/drivers/dma/sdxi/device.c
> index f9787d7190d4..d5a5b8d43391 100644
> --- a/drivers/dma/sdxi/device.c
> +++ b/drivers/dma/sdxi/device.c
> @@ -212,6 +212,36 @@ static int sdxi_dev_stop(struct sdxi_dev *sdxi)
>  	return sdxi->bus_ops->reset ? sdxi->bus_ops->reset(sdxi) : -EIO;
>  }
>
> +/*
> + * Activate a stopped function. GSRV_ACTIVE takes it through the
> + * transient GSV_INIT state to GSV_ACTIVE or GSV_ERROR. See SDXI 1.0
> + * 4.1.8.9.
> + */
> +static int sdxi_dev_start(struct sdxi_dev *sdxi)
> +{
> +	const unsigned long settled = BIT(SDXI_GSV_ACTIVE) | BIT(SDXI_GSV_ERROR);
> +	enum sdxi_fn_gsv gsv = sdxi_dev_gsv(sdxi);
> +
> +	if (gsv != SDXI_GSV_STOP) {
> +		dev_err(sdxi->dev,
> +			"start: MMIO_STS0.fn_gsv = %#x (%s) on entry\n",
> +			gsv, gsv_str(gsv));
> +		return -EBUSY;
> +	}
> +
> +	sdxi_write_fn_gsr(sdxi, SDXI_GSRV_ACTIVE);
> +
> +	if (sdxi_dev_gsv_poll(sdxi, gsv, BIT(gsv) & settled) ||
> +	    gsv != SDXI_GSV_ACTIVE) {
> +		dev_err(sdxi->dev,
> +			"start: MMIO_STS0.fn_gsv = %#x (%s) after activate\n",
> +			gsv, gsv_str(gsv));
> +		return -EIO;
> +	}
> +
> +	return 0;
> +}
> +
>  /* Stop the function and discard inherited MMIO configuration. */
>  static int sdxi_fn_prepare(struct sdxi_dev *sdxi)
>  {
> @@ -361,7 +391,20 @@ static int sdxi_fn_activate(struct sdxi_dev *sdxi)
>  	if (err)
>  		return err;
>
> -	return 0;
> +	/*
> +	 * SDXI 1.0 4.1.8.9: Set MMIO_CTL0.fn_gsr to GSRV_ACTIVE and
> +	 * wait for MMIO_STS0.fn_gsv to reach GSV_ACTIVE or GSV_ERROR.
> +	 *
> +	 * We haven't queued any descriptors to the admin context at
> +	 * this point, so the admin context jump start (SDXI 1.0
> +	 * 4.1.8.10.b) is accomplished later when other
> +	 * code starts client contexts.
> +	 */
> +	err = sdxi_dev_start(sdxi);
> +	if (err)
> +		sdxi_dev_stop(sdxi);

Suppose should stop() in start() before return error. Generally function
should cleanup resource that already allocated in the function before return
fail.

Frank
> +
> +	return err;
>  }
>
>  static int sdxi_device_init(struct sdxi_dev *sdxi)
> @@ -407,6 +450,14 @@ int sdxi_register(struct device *dev, const struct sdxi_bus_ops *ops)
>  }
>  EXPORT_SYMBOL_NS_GPL(sdxi_register, "SDXI");
>
> +void sdxi_unregister(struct device *dev)
> +{
> +	struct sdxi_dev *sdxi = dev_get_drvdata(dev);
> +
> +	sdxi_dev_stop(sdxi);
> +}
> +EXPORT_SYMBOL_NS_GPL(sdxi_unregister, "SDXI");
> +
>  MODULE_AUTHOR("Wei Huang");
>  MODULE_AUTHOR("Nathan Lynch");
>  MODULE_DESCRIPTION("SDXI core");
> diff --git a/drivers/dma/sdxi/pci.c b/drivers/dma/sdxi/pci.c
> index 6a293db69199..d196ab5cf6f1 100644
> --- a/drivers/dma/sdxi/pci.c
> +++ b/drivers/dma/sdxi/pci.c
> @@ -99,6 +99,7 @@ static int sdxi_pci_probe(struct pci_dev *pdev,
>
>  static void sdxi_pci_remove(struct pci_dev *pdev)
>  {
> +	sdxi_unregister(&pdev->dev);
>  	pci_disable_sriov(pdev);
>  }
>
> diff --git a/drivers/dma/sdxi/sdxi.h b/drivers/dma/sdxi/sdxi.h
> index 525473029987..631a605ea62f 100644
> --- a/drivers/dma/sdxi/sdxi.h
> +++ b/drivers/dma/sdxi/sdxi.h
> @@ -68,6 +68,7 @@ struct sdxi_dev {
>  };
>
>  int sdxi_register(struct device *dev, const struct sdxi_bus_ops *ops);
> +void sdxi_unregister(struct device *dev);
>
>  static inline u64 sdxi_read64(const struct sdxi_dev *sdxi, enum sdxi_reg reg)
>  {
>
> --
> 2.56.0
>