Hi all, On 11/16/20 10:19 AM, Christoph Hellwig wrote: > I just noticed this showing up in Linus' tree and I'm not happy. > > This whole model of the DMA subdevices in remoteproc is simply broken. > > We really need to change the virtio code pass an expicit DMA device ( > similar to what e.g. the USB and RDMA code does), instead of faking up > devices with broken adhoc inheritance of DMA properties and magic poking > into device parent relationships. For your formation I started some stuff on my side to be able to declare the virtio device in DT as a remoteproc child node. https://lkml.org/lkml/2020/4/16/1817 Quite big refactoring, but could be a way to answer... Regards, Arnaud > > Bjorn, I thought you were going to look into this a while ago? > > > 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: >> >> [ 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; >> >> /* Increase device refcnt to avoid freeing it */ >> get_device(buf->dev); >> -- >> 2.29.2 >> >> > ---end quoted text--- >
