linux-kernel - Re: [PATCH 4/7] dmaengine: sprd: Add device validation to support multiple controllers

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Message-ID: <CAMz4ku+ctQrcR+6t1ouakeG3dbgL3qR8fz-Hft4s9FnxtFL1ng@mail.gmail.com>
Date:   Tue, 30 Apr 2019 13:30:45 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     Vinod Koul <vkoul@...nel.org>
Cc:     Dan Williams <dan.j.williams@...el.com>, eric.long@...soc.com,
        Orson Zhai <orsonzhai@...il.com>,
        Chunyan Zhang <zhang.lyra@...il.com>,
        Mark Brown <broonie@...nel.org>, dmaengine@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/7] dmaengine: sprd: Add device validation to support
 multiple controllers

On Mon, 29 Apr 2019 at 22:05, Vinod Koul <vkoul@...nel.org> wrote:
>
> On 29-04-19, 20:20, Baolin Wang wrote:
> > On Mon, 29 Apr 2019 at 19:57, Vinod Koul <vkoul@...nel.org> wrote:
> > >
> > > On 15-04-19, 20:14, Baolin Wang wrote:
> > > > From: Eric Long <eric.long@...soc.com>
> > > >
> > > > Since we can support multiple DMA engine controllers, we should add
> > > > device validation in filter function to check if the correct controller
> > > > to be requested.
> > > >
> > > > Signed-off-by: Eric Long <eric.long@...soc.com>
> > > > Signed-off-by: Baolin Wang <baolin.wang@...aro.org>
> > > > ---
> > > >  drivers/dma/sprd-dma.c |    5 +++++
> > > >  1 file changed, 5 insertions(+)
> > > >
> > > > diff --git a/drivers/dma/sprd-dma.c b/drivers/dma/sprd-dma.c
> > > > index 0f92e60..9f99d4b 100644
> > > > --- a/drivers/dma/sprd-dma.c
> > > > +++ b/drivers/dma/sprd-dma.c
> > > > @@ -1020,8 +1020,13 @@ static void sprd_dma_free_desc(struct virt_dma_desc *vd)
> > > >  static bool sprd_dma_filter_fn(struct dma_chan *chan, void *param)
> > > >  {
> > > >       struct sprd_dma_chn *schan = to_sprd_dma_chan(chan);
> > > > +     struct of_phandle_args *dma_spec =
> > > > +             container_of(param, struct of_phandle_args, args[0]);
> > > >       u32 slave_id = *(u32 *)param;
> > > >
> > > > +     if (chan->device->dev->of_node != dma_spec->np)
> > >
> > > Are you not using of_dma_find_controller() that does this, so this would
> > > be useless!
> >
> > Yes, we can use of_dma_find_controller(), but that will be a little
> > complicated than current solution. Since we need introduce one
> > structure to save the node to validate in the filter function like
> > below, which seems make things complicated. But if you still like to
> > use of_dma_find_controller(), I can change to use it in next version.
>
> Sorry I should have clarified more..
>
> of_dma_find_controller() is called by xlate, so you already run this
> check, so why use this :)

The of_dma_find_controller() can save the requested device node into
dma_spec, and in the of_dma_simple_xlate() function, it will call
dma_request_channel() to request one channel, but it did not validate
the device node to find the corresponding dma device in
dma_request_channel(). So we should in our filter function to validate
the device node with the device node specified by the dma_spec. Hope I
make things clear.

-- 
Baolin Wang
Best Regards