Hi Laurent, Dave,

On Mon, 2020-05-04 at 12:26 +0300, Laurent Pinchart wrote:
> From: Dave Stevenson <dave.stevenson@raspberrypi.org>
> 
> vchiq on Pi4 is no longer under the soc node, therefore it
> doesn't get the dma-ranges for the VPU.

This is not true in upstream's device-tree, and AFAIK, from a HW perspective,
the VPU interface didn't change interconnects, it's still connected to /soc
(highlighted by the fact that it has its DMA limitations).

Why did you found the need to move vchiq into /scb downstream?

> Switch to using the configuration of the old dma controller as
> that will set the dma-ranges correctly.

Ultimately, this is no different than copying DMA constraints from, say, the
I2C bus controller. The fact that this is a DMA controller has nothing to with
VPU's view of the system's memory (which dma-ranges symbolizes).

BTW, Laurent, I learned all about DMA trough one of your talks, it really
helped to set everything in place at the time :).

Regards,
Nicolas

> Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.org>
> Signed-off-by: Jacopo Mondi <jacopo@jmondi.org>
> ---
>  .../interface/vchiq_arm/vchiq_arm.c             | 17 ++++++++++++++---
>  1 file changed, 14 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> index 15ccd624aaab..d1a556f16499 100644
> --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> @@ -2719,6 +2719,7 @@ vchiq_register_child(struct platform_device *pdev, const
> char *name)
>  {
>  	struct platform_device_info pdevinfo;
>  	struct platform_device *child;
> +	struct device_node *np;
>  
>  	memset(&pdevinfo, 0, sizeof(pdevinfo));
>  
> @@ -2734,10 +2735,20 @@ vchiq_register_child(struct platform_device *pdev,
> const char *name)
>  	}
>  
>  	/*
> -	 * We want the dma-ranges etc to be copied from the parent VCHIQ device
> -	 * to be passed on to the children too.
> +	 * We want the dma-ranges etc to be copied from a device with the
> +	 * correct dma-ranges for the VPU.
> +	 * VCHIQ on Pi4 is now under scb which doesn't get those dma-ranges.
> +	 * Take the "dma" node as going to be suitable as it sees the world
> +	 * through the same eyes as the VPU.
>  	 */
> -	of_dma_configure(&new_dev->dev, pdev->dev.of_node, true);
> +	np = of_find_node_by_path("dma");
> +	if (!np)
> +		np = pdev->dev.of_node;
> +
> +	of_dma_configure(&child->dev, np, true);
> +
> +	if (np != pdev->dev.of_node)
> +		of_node_put(np);
>  
>  	return child;
>  }