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

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Date:   Mon, 09 Apr 2018 17:55:40 +0200
From:   Heiko Stübner <heiko@...ech.de>
To:     Robin Murphy <robin.murphy@....com>
Cc:     Tomeu Vizoso <tomeu@...euvizoso.net>,
        Jeffy Chen <jeffy.chen@...k-chips.com>,
        open list <linux-kernel@...r.kernel.org>, jcliang@...omium.org,
        simon xue <xxm@...k-chips.com>, tfiga@...omium.org,
        Romain Perier <romain.perier@...labora.com>,
        Yakir Yang <kuankuan.y@...il.com>,
        Arnd Bergmann <arnd@...db.de>, Liang Chen <cl@...k-chips.com>,
        Rob Herring <robh+dt@...nel.org>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Catalin Marinas <catalin.marinas@....com>,
        David Wu <david.wu@...k-chips.com>,
        Finley Xiao <finley.xiao@...k-chips.com>,
        Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Jacob Chen <jacob-chen@...wrt.com>,
        Kever Yang <kever.yang@...k-chips.com>,
        Brian Norris <briannorris@...omium.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        Rocky Hao <rocky.hao@...k-chips.com>,
        Will Deacon <will.deacon@....com>,
        Nickey Yang <nickey.yang@...k-chips.com>,
        devicetree@...r.kernel.org, Mark Yao <markyao0591@...il.com>,
        Russell King <linux@...linux.org.uk>,
        linux-arm-kernel@...ts.infradead.org,
        Sugar Zhang <sugar.zhang@...k-chips.com>,
        Caesar Wang <wxt@...k-chips.com>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [PATCH v8 07/14] ARM: dts: rockchip: add clocks in iommu nodes

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 ;-)