On 2020/11/5 下午8:22, Alexander Lobakin wrote:
From: Jason Wang <jasowang@xxxxxxxxxx>
Date: Thu, 5 Nov 2020 11:10:24 +0800
Hi Jason,
On 2020/11/4 下午11:31, 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;
I wonder it could be the right time to introduce dma_dev for virtio
instead of depending on something magic via parent.
This patch are meant to hit RC window and stable trees as a fix of
the bug that is present since v5.8-rc1. So any new features are out
of scope of this particular fix.
Right.
The idea of DMAing through "dev->parent" is that "virtioX" itself is a
logical dev, not the real one, but its parent *is*. This logic is used
across the whole tree -- every subsystem creates its own logical device,
but drivers should always use the backing PCI/platform/etc. devices for
DMA operations, which represent the real hardware.
Yes, so what I meant is to use different variables for DMA and
hierarchy. So it's the responsibility of the lower layer to pass a
correct "dma_dev" to the upper layer instead of depending parent.
Anyway for this patch.
Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
Thanks
(Btw I don't even notice that there's transport specific code in virtio
console, it's better to avoid it)
Thanks
Thanks,
Al
/* Increase device refcnt to avoid freeing it */
get_device(buf->dev);
