Re: virtio remoteproc device

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Apr 23, 2018 at 08:55:57AM +0000, Loic PALLARDY wrote:
> 
> 
> > -----Original Message-----
> > From: linux-remoteproc-owner@vger.kernel.org [mailto:linux-remoteproc-
> > owner@vger.kernel.org] On Behalf Of Anup Patel
> > Sent: Sunday, April 22, 2018 6:08 AM
> > To: Michael S. Tsirkin <mst@redhat.com>
> > Cc: linux-remoteproc@vger.kernel.org; Ohad Ben-Cohen
> > <ohad@wizery.com>; Bjorn Andersson <bjorn.andersson@linaro.org>;
> > virtualization@lists.linux-foundation.org
> > Subject: Re: virtio remoteproc device
> > 
> > On Fri, Apr 20, 2018 at 10:23 PM, Michael S. Tsirkin <mst@redhat.com>
> > wrote:
> > > Hello!
> > > I note the following in the serial console:
> > >
> > >       if (is_rproc_serial(vdev)) {
> > >                 /*
> > >                  * 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.
> > >                  */
> > >                 if (!vdev->dev.parent || !vdev->dev.parent->parent)
> > >                         goto free_buf;
> > >                 buf->dev = vdev->dev.parent->parent;
> > >
> > >                 /* Increase device refcnt to avoid freeing it */
> > >                 get_device(buf->dev);
> > >                 buf->buf = dma_alloc_coherent(buf->dev, buf_size, &buf->dma,
> > >                                               GFP_KERNEL);
> > >         }
> > >
> > > Added here:
> > >         commit 1b6370463e88b0c1c317de16d7b962acc1dab4f2
> > >         Author: Sjur Br�ndeland <sjur.brandeland@stericsson.com>
> > >         Date:   Fri Dec 14 14:40:51 2012 +1030
> > >
> > >     virtio_console: Add support for remoteproc serial
> > >
> > >
> > > I am not familiar with rproc so I have a question:
> > > why is it required to use coherent memory here,
> > > and why through a grandparent device?
> > 
> > I faced similar issue when I tried VirtIO RPMSG bus over
> > VirtIO MMIO transport.
> > 
> > Here's my fix for VirtIO RPMSG bus driver:
> > https://patchwork.kernel.org/patch/10155145/
> 
> Hi Anup and Michael,
> 
> I pushed a series to modify virtio device allocation in remoteproc. Please see [1].
> It allows to remove allocation based on "grand-parent" device in the case of virtio device allocated by remoteproc.
> Virto_console patch missing, only virtio_rpmsg modification proposed. I can add it in next version.
> 
> Regards,
> Loic
> 
> [1] https://lkml.org/lkml/2018/3/1/644

Thanks!
Based on that patch, can remoteproc force VIRTIO_F_IOMMU_PLATFORM
in features and then drop special-casing of dma completely?

> > 
> > Regards,
> > Anup
> > --
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