Re: [PATCH 07/15] accel/qda: Add memory manager for CB devices

[Dmitry Baryshkov]

On Tue, May 19, 2026 at 11:45:57AM +0530, Ekansh Gupta via B4 Relay wrote:
> From: Ekansh Gupta <ekansh.gupta@xxxxxxxxxxxxxxxx>
> 
> Introduce the QDA memory manager (qda_memory_manager) to track and
> manage the IOMMU devices that back each compute context bank (CB).
> 
> Each CB device registered on the qda-compute-cb bus is assigned a
> unique ID via an XArray and wrapped in a qda_iommu_device descriptor
> that records the device pointer and its stream ID. This registry
> allows the driver to look up the correct IOMMU domain for a given
> session when mapping DSP buffers.
> 
> The memory manager is initialised in qda_init_device() before CB
> devices are populated and torn down in qda_deinit_device() after they
> are destroyed, ensuring no dangling references remain in the XArray.
> 
> qda_cb.c is extended with qda_cb_setup_device(), which is called
> immediately after a CB device is registered on the bus. It allocates
> a qda_iommu_device, registers it with the memory manager, and stores
> it as the CB device's driver data so that qda_destroy_cb_device() can
> retrieve and unregister it during teardown.
> 
> Assisted-by: Claude:claude-4-6-sonnet
> Signed-off-by: Ekansh Gupta <ekansh.gupta@xxxxxxxxxxxxxxxx>
> ---
>  drivers/accel/qda/Makefile             |   1 +
>  drivers/accel/qda/qda_cb.c             |  47 ++++++++++++++
>  drivers/accel/qda/qda_drv.c            |  34 ++++++++++
>  drivers/accel/qda/qda_drv.h            |   5 ++
>  drivers/accel/qda/qda_memory_manager.c | 111 +++++++++++++++++++++++++++++++++
>  drivers/accel/qda/qda_memory_manager.h |  49 +++++++++++++++
>  drivers/accel/qda/qda_rpmsg.c          |   7 +++
>  7 files changed, 254 insertions(+)
> 
> @@ -61,14 +62,20 @@ static int qda_rpmsg_probe(struct rpmsg_device *rpdev)
>  	}
>  	qdev->dsp_name = label;
>  
> +	ret = qda_init_device(qdev);
> +	if (ret)
> +		return ret;
> +
>  	ret = qda_cb_populate(qdev, rpdev->dev.of_node);
>  	if (ret) {
>  		dev_err(qdev->dev, "Failed to populate child devices: %d\n", ret);
> +		qda_deinit_device(qdev);
>  		return ret;
>  	}
>  
>  	ret = qda_register_device(qdev);
>  	if (ret) {
> +		qda_deinit_device(qdev);
>  		qda_cb_unpopulate(qdev);

No, this is not how you unwind in the error case in the kernel. Follow
the established patterns.

>  		return ret;
>  	}
> 
> -- 
> 2.34.1
> 
> 

-- 
With best wishes
Dmitry