linux-kernel - Re: [PATCH v2 13/16] remoteproc: look-up memory-device for virtio device allocation

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Date:   Wed, 13 Dec 2017 21:32:48 -0800
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Loic Pallardy <loic.pallardy@...com>
Cc:     ohad@...ery.com, linux-remoteproc@...r.kernel.org,
        linux-kernel@...r.kernel.org, arnaud.pouliquen@...com,
        benjamin.gaignard@...aro.org
Subject: Re: [PATCH v2 13/16] remoteproc: look-up memory-device for virtio
 device allocation

On Thu 30 Nov 08:46 PST 2017, Loic Pallardy wrote:

> This patch parse existing carveout list to find a memory area
> matching on "vdev<vdev_id>buffer" name.
> If found, memory device will be used as parent for vdev creation, else
> rproc platform device will be used as today.
> 
> Signed-off-by: Loic Pallardy <loic.pallardy@...com>
> ---
>  drivers/remoteproc/remoteproc_core.c   | 13 +++++++++++++
>  drivers/remoteproc/remoteproc_virtio.c |  2 +-
>  include/linux/remoteproc.h             |  1 +
>  3 files changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/remoteproc/remoteproc_core.c b/drivers/remoteproc/remoteproc_core.c
> index 6b5e2b2..9c12319 100644
> --- a/drivers/remoteproc/remoteproc_core.c
> +++ b/drivers/remoteproc/remoteproc_core.c
> @@ -583,8 +583,11 @@ static int rproc_handle_vdev(struct rproc *rproc, struct fw_rsc_vdev *rsc,
>  {
>  	struct device *dev = &rproc->dev;
>  	struct rproc_vdev *rvdev;
> +	struct device *memdev = dev->parent;
> +	struct rproc_mem_entry *carveout;
>  	int i, ret;
>  	static int index;
> +	char name[16];
>  
>  	/* make sure resource isn't truncated */
>  	if (sizeof(*rsc) + rsc->num_of_vrings * sizeof(struct fw_rsc_vdev_vring)
> @@ -637,6 +640,16 @@ static int rproc_handle_vdev(struct rproc *rproc, struct fw_rsc_vdev *rsc,
>  
>  	list_add_tail(&rvdev->node, &rproc->rvdevs);
>  
> +	/* Find associated registered carveout. */
> +	/* Try dedicated vdev buffer pool. */
> +	snprintf(name, sizeof(name), "vdev%dbuffer", rvdev->index);
> +	carveout = rproc_find_carveout_by_name(rproc, name);
> +
> +	if (carveout && carveout->memdev)
> +		memdev = &carveout->memdev->dev;
> +
> +	rvdev->dev = memdev;
> +
>  	rproc_add_subdev(rproc, &rvdev->subdev,
>  			 rproc_vdev_do_probe, rproc_vdev_do_remove);
>  
> diff --git a/drivers/remoteproc/remoteproc_virtio.c b/drivers/remoteproc/remoteproc_virtio.c
> index 2946348..1f7a444 100644
> --- a/drivers/remoteproc/remoteproc_virtio.c
> +++ b/drivers/remoteproc/remoteproc_virtio.c
> @@ -303,7 +303,7 @@ static void rproc_virtio_dev_release(struct device *dev)
>  int rproc_add_virtio_dev(struct rproc_vdev *rvdev, int id)
>  {
>  	struct rproc *rproc = rvdev->rproc;
> -	struct device *dev = &rproc->dev;
> +	struct device *dev = rvdev->dev;

This will cause the device structure to change shape based on there
being a match of a carveout or not.


I also think it's preferable to limit the life cycle of the allocations
in this memory region to a single start->stop cycle, rather than
boot->shutdown.

So I think it makes more sense to use the vdev->dev and
dmam_declare_coherent_memory on this. But as in the previous patch this
can't be a carveout that has been remapped already.


A somewhat unrelated topic to this is the ability to associate DT nodes
to rpmsg devices (I do this for the Qualcomm children), in this case we
would have a DT node per vdev under the remoteproc, perhaps it would
make more sense to introduce that and put the memory-region in that
node. Only thin that comes to mind is that we still need to match a
carveout in the resource table, in order to communicate the buffer
region to the remote side for your memory protection purposes.

Regards,
Bjorn