linux-kernel - Re: [PATCH 3/4] ACPI: Introduce DMA ranges parsing

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Date:   Wed, 26 Jul 2017 02:27:08 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Robin Murphy <robin.murphy@....com>,
        Will Deacon <will.deacon@....com>,
        Robert Moore <robert.moore@...el.com>,
        Hanjun Guo <hanjun.guo@...aro.org>, Feng Kan <fkan@....com>,
        Jon Masters <jcm@...hat.com>, Zhang Rui <rui.zhang@...el.com>,
        Nate Watterson <nwatters@...eaurora.org>
Subject: Re: [PATCH 3/4] ACPI: Introduce DMA ranges parsing

On Tuesday, July 25, 2017 10:06:15 AM Lorenzo Pieralisi wrote:
> On Mon, Jul 24, 2017 at 08:42:15PM +0200, Rafael J. Wysocki wrote:
> > On Mon, Jul 24, 2017 at 12:40 PM, Lorenzo Pieralisi
> > <lorenzo.pieralisi@....com> wrote:
> > > On Sat, Jul 22, 2017 at 12:15:42AM +0200, Rafael J. Wysocki wrote:
> > >
> > 
> > [cut]
> > 
> > >
> > >> > +           return -EINVAL;
> > >> > +   }
> > >> > +
> > >> > +   ret = acpi_dev_get_dma_resources(adev, &list);
> > >> > +   if (ret > 0) {
> > >> > +           list_for_each_entry(rentry, &list, node) {
> > >> > +                   if (dma_offset && rentry->offset != dma_offset) {
> > >> > +                           ret = -EINVAL;
> > >> > +                           pr_warn("Can't handle multiple windows with different offsets\n");
> > >> > +                           goto out;
> > >> > +                   }
> > >> > +                   dma_offset = rentry->offset;
> > >> > +
> > >> > +                   /* Take lower and upper limits */
> > >> > +                   if (rentry->res->start < dma_start)
> > >> > +                           dma_start = rentry->res->start;
> > >> > +                   if (rentry->res->end > dma_end)
> > >> > +                           dma_end = rentry->res->end;
> > >> > +           }
> > >> > +
> > >> > +           if (dma_start >= dma_end) {
> > >> > +                   ret = -EINVAL;
> > >> > +                   pr_warn("Invalid DMA regions configuration\n");
> > >>
> > >> dev_warn()?
> > >>
> > >> And why _warn() and not _info()?
> > >
> > > Mmm..ok for the dev_ prefix - basically this would be a FW_BUG (I think
> > > this specific error condition is overkill TBH, the ACPI resource
> > > validation code should catch it before we even get here) not sure
> > > about downgrading it to _info() though, I would leave it at this
> > > loglevel - in particular in the offset check above:
> > >
> > >         if (dma_offset && rentry->offset != dma_offset) {
> > >                 ret = -EINVAL;
> > >                 pr_warn("Can't handle multiple windows with different offsets\n");
> > >                 goto out;
> > >         }
> > 
> > Well, so the "why" question above still has no answer ...
> 
> It is a firmware misconfiguration, we end up dismissing firmware
> information and use the device with default/possibly misconfigured
> DMA windows (ie offset == 0) for that platform, that's the reason
> why I thought it would deserve a _warn rather than _info loglevel.

Well, _warn only makes it slightly more visible for people with somewhat
unusual logging configurations, but fair enough.

Thanks,
Rafael