linux-kernel - Re: [PATCH virtio] virtio: virtio_console: fix DMA memory allocation for rproc serial

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Message-ID: <20201116162844.GB16619@infradead.org>
Date:   Mon, 16 Nov 2020 16:28:44 +0000
From:   Christoph Hellwig <hch@...radead.org>
To:     Arnaud POULIQUEN <arnaud.pouliquen@...com>
Cc:     Christoph Hellwig <hch@...radead.org>,
        Alexander Lobakin <alobakin@...me>,
        Amit Shah <amit@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Suman Anna <s-anna@...com>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Ohad Ben-Cohen <ohad@...ery.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        Jason Wang <jasowang@...hat.com>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "linux-remoteproc@...r.kernel.org" <linux-remoteproc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH virtio] virtio: virtio_console: fix DMA memory allocation
 for rproc serial

On Mon, Nov 16, 2020 at 11:46:59AM +0100, Arnaud POULIQUEN wrote:
> 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...

Yes, that series is exactly what we need to do conceptually (can't
comment on all the nitty grity details as I'm not too familiar with
the remoteproc code).