Re: [PATCH v8 07/14] ARM: dts: rockchip: add clocks in iommu nodes

From: "Heiko Stübner" <heiko@sntech.de>
To: Robin Murphy <robin.murphy@arm.com>
Cc: Tomeu Vizoso <tomeu@tomeuvizoso.net>,
	Jeffy Chen <jeffy.chen@rock-chips.com>,
	open list <linux-kernel@vger.kernel.org>,
	jcliang@chromium.org, simon xue <xxm@rock-chips.com>,
	tfiga@chromium.org, Romain Perier <romain.perier@collabora.com>,
	Yakir Yang <kuankuan.y@gmail.com>, Arnd Bergmann <arnd@arndb.de>,
	Liang Chen <cl@rock-chips.com>, Rob Herring <robh+dt@kernel.org>,
	Shawn Lin <shawn.lin@rock-chips.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	David Wu <david.wu@rock-chips.com>,
	Finley Xiao <finley.xiao@rock-chips.com>,
	Enric Balletbo i Serra <enric.balletbo@collabora.com>,
	Jacob Chen <jacob-chen@iotwrt.com>,
	Kever Yang <kever.yang@rock-chips.com>,
	Brian Norris <briannorris@chromium.org>,
	"open list:ARM/Rockchip SoC..."
	<linux-rockchip@lists.infradead.org>,
	Rocky Hao <rocky.hao@rock-chips.com>,
	Will Deacon <will.deacon@arm.com>,
	Nickey Yang <nickey.yang@rock-chips.com>,
	devicetree@vger.kernel.org, Mark Yao <markyao0591@gmail.com>,
	Russell King <linux@armlinux.org.uk>,
	linux-arm-kernel@lists.infradead.org,
	Sugar Zhang <sugar.zhang@rock-chips.com>,
	Caesar Wang <wxt@rock-chips.com>,
	Mark Rutland <mark.rutland@arm.com>
Subject: Re: [PATCH v8 07/14] ARM: dts: rockchip: add clocks in iommu nodes
Date: Mon, 09 Apr 2018 17:55:40 +0200	[thread overview]
Message-ID: <2255884.b1SkkUdh3X@diego> (raw)
In-Reply-To: <df522a01-6f4a-bb96-4423-19965b078a1b@arm.com>

Am Montag, 9. April 2018, 17:53:01 CEST schrieb Robin Murphy:
> On 09/04/18 16:44, Heiko Stübner wrote:
> > Hi Tomeu,
> > 
> > Am Montag, 9. April 2018, 16:41:56 CEST schrieb Tomeu Vizoso:
> >> in today's linux-next, the DRM driver fails to probe because the iommu
> >> driver fails to find the aclk. I need to apply this patch for things
> >> to work again.
> > 
> > Thanks for catching that issue.
> > 
> > This seems to expose a backwards-compatibility issue, as this breaks
> > all old devicetrees, so should get a proper fix, apart from me applying
> > the dt-patch I missed.
> > 
> > Looking at the iommu-clock-handling patch, I imagine this part as
> > the culprit:
> > 
> > +	iommu->num_clocks = ARRAY_SIZE(rk_iommu_clocks);
> > +	iommu->clocks = devm_kcalloc(iommu->dev, iommu->num_clocks,
> > +				     sizeof(*iommu->clocks), GFP_KERNEL);
> > +	if (!iommu->clocks)
> > +		return -ENOMEM;
> > 
> > The clk-bulk functions seem to work with simple for loops and
> > should (as the other standard clock functions) just work fine with
> > an empty struct, so I guess a simple
> > 
> > 	if (!iommu->clocks && iommu->num_clocks > 0)
> > 	
> > 		return -ENOMEM;
> > 
> > should hopefully be enough. I'll try to give this a test later on
> > if nobody beats me to it :-)
> 
> But iommu->num_clocks is clearly set to a nonzero compile-time constant
> at this point ;)
> 
> I'd assume it's the return from devm_clk_bulk_get() which needs to
> special-case the "no clocks found" case from any other error, and *then*
> blat num_clocks to 0 if so.

you're right of course. Looking at it again, I now clearly see the ARRAY_SIZE
and am wondering what made me think num_clocks would be runtime-read.

Must be those 25°C today ;-)