On Wed, Nov 04, 2020 at 03:31:36PM +0000, Alexander Lobakin wrote:
> Since commit 086d08725d34 ("remoteproc: create vdev subdevice with
> specific dma memory pool"), every remoteproc has a DMA subdevice
> ("remoteprocX#vdevYbuffer") for each virtio device, which inherits
> DMA capabilities from the corresponding platform device. This allowed
> to associate different DMA pools with each vdev, and required from
> virtio drivers to perform DMA operations with the parent device
> (vdev->dev.parent) instead of grandparent (vdev->dev.parent->parent).
>
> virtio_rpmsg_bus was already changed in the same merge cycle with
> commit d999b622fcfb ("rpmsg: virtio: allocate buffer from parent"),
> but virtio_console did not. In fact, operations using the grandparent
> worked fine while the grandparent was the platform device, but since
> commit c774ad010873 ("remoteproc: Fix and restore the parenting
> hierarchy for vdev") this was changed, and now the grandparent device
> is the remoteproc device without any DMA capabilities.
> So, starting v5.8-rc1 the following warning is observed:
>
> [ 2.483925] ------------[ cut here ]------------
> [ 2.489148] WARNING: CPU: 3 PID: 101 at kernel/dma/mapping.c:427 0x80e7eee8
> [ 2.489152] Modules linked in: virtio_console(+)
> [ 2.503737] virtio_rpmsg_bus rpmsg_core
> [ 2.508903]
> [ 2.528898] <Other modules, stack and call trace here>
> [ 2.913043]
> [ 2.914907] ---[ end trace 93ac8746beab612c ]---
> [ 2.920102] virtio-ports vport1p0: Error allocating inbufs
>
> kernel/dma/mapping.c:427 is:
>
> WARN_ON_ONCE(!dev->coherent_dma_mask);
>
> obviously because the grandparent now is remoteproc dev without any
> DMA caps:
You are correct.
>
> [ 3.104943] Parent: remoteproc0#vdev1buffer, grandparent: remoteproc0
>
> Fix this the same way as it was for virtio_rpmsg_bus, using just the
> parent device (vdev->dev.parent, "remoteprocX#vdevYbuffer") for DMA
> operations.
> This also allows now to reserve DMA pools/buffers for rproc serial
> via Device Tree.
>
> Fixes: c774ad010873 ("remoteproc: Fix and restore the parenting hierarchy for vdev")
> Cc: stable@xxxxxxxxxxxxxxx # 5.1+
> Signed-off-by: Alexander Lobakin <alobakin@xxxxx>
> ---
> drivers/char/virtio_console.c | 8 ++++----
> 1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> index a2da8f768b94..1836cc56e357 100644
> --- a/drivers/char/virtio_console.c
> +++ b/drivers/char/virtio_console.c
> @@ -435,12 +435,12 @@ static struct port_buffer *alloc_buf(struct virtio_device *vdev, size_t buf_size
> /*
> * Allocate DMA memory from ancestor. When a virtio
> * device is created by remoteproc, the DMA memory is
> - * associated with the grandparent device:
> - * vdev => rproc => platform-dev.
> + * associated with the parent device:
> + * virtioY => remoteprocX#vdevYbuffer.
> */
> - if (!vdev->dev.parent || !vdev->dev.parent->parent)
> + buf->dev = vdev->dev.parent;
> + if (!buf->dev)
> goto free_buf;
> - buf->dev = vdev->dev.parent->parent;
Reviewed-by: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
>
> /* Increase device refcnt to avoid freeing it */
> get_device(buf->dev);
> --
> 2.29.2
>
>
