linux-kernel - Re: [PATCH 2/5] media: platform: Aspeed: Make reserved memory optional

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Date:   Wed, 03 Apr 2019 22:16:34 -0400
From:   "Andrew Jeffery" <andrew@...id.au>
To:     "Eddie James" <eajames@...ux.vnet.ibm.com>,
        "Eddie James" <eajames@...ux.ibm.com>, linux-media@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, linux-aspeed@...ts.ozlabs.org,
        "Joel Stanley" <joel@....id.au>,
        "Mauro Carvalho Chehab" <mchehab@...nel.org>,
        linux-clk@...r.kernel.org, "Stephen Boyd" <sboyd@...nel.org>,
        "Michael Turquette" <mturquette@...libre.com>,
        devicetree@...r.kernel.org, mark.rutland@....com,
        "Rob Herring" <robh+dt@...nel.org>
Subject: Re: [PATCH 2/5] media: platform: Aspeed: Make reserved memory optional



On Thu, 4 Apr 2019, at 01:05, Eddie James wrote:
> 
> On 4/3/19 1:01 AM, Andrew Jeffery wrote:
> >
> > On Wed, 3 Apr 2019, at 04:55, Eddie James wrote:
> >> Reserved memory doesn't need to be required; system memory would work
> >> fine.
> > I had to do a bit of legwork to understand what you were doing here. My
> > understanding is that we allocate out of the default CMA region if the
> > memory-region property isn't specified. Is that what you're expecting?
> > Could be helpful to be a little less terse in the commit message.
> 
> 
> Correct.
> 
> 
> >
> >> Signed-off-by: Eddie James <eajames@...ux.ibm.com>
> >> ---
> >>   drivers/media/platform/aspeed-video.c | 6 +-----
> >>   1 file changed, 1 insertion(+), 5 deletions(-)
> >>
> >> diff --git a/drivers/media/platform/aspeed-video.c
> >> b/drivers/media/platform/aspeed-video.c
> >> index 55c55a6..8144fe3 100644
> >> --- a/drivers/media/platform/aspeed-video.c
> >> +++ b/drivers/media/platform/aspeed-video.c
> >> @@ -1608,11 +1608,7 @@ static int aspeed_video_init(struct aspeed_video
> >> *video)
> >>   		return PTR_ERR(video->vclk);
> >>   	}
> >>   
> >> -	rc = of_reserved_mem_device_init(dev);
> >> -	if (rc) {
> >> -		dev_err(dev, "Unable to reserve memory\n");
> >> -		return rc;
> >> -	}
> >> +	of_reserved_mem_device_init(dev);
> > You're ignoring *all* errors here with the expectation that the cause is the
> > missing memory-region property. However, other errors can propagate
> > out of of_reserved_mem_device_init() - e.g. ENOMEM. Rather than remove
> > error checking, I think you should explicitly test for ENODEV, which is what is
> > returned if the memory-region property is absent.
> 
> 
> But it doesn't matter if it fails for any reason, any DMA allocation 
> should fall back to default CMA memory. In the case of ENOMEM or other 
> errors, then the later calls to allocate DMA may fail and we can deal 
> with it then.

Fair enough then. I think it deserves a comment, but up to you.

Andrew