Re: [PATCH 1/2] edac: sifive: Add DT documentation for SiFive L2 cache Controller

From: Rob Herring <robh@kernel.org>
To: Borislav Petkov <bp@alien8.de>
Cc: James Morse <james.morse@arm.com>,
	Yash Shah <yash.shah@sifive.com>,
	linux-riscv@lists.infradead.org, linux-edac@vger.kernel.org,
	Palmer Dabbelt <palmer@sifive.com>,
	Paul Walmsley <paul.walmsley@sifive.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Albert Ou <aou@eecs.berkeley.edu>,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	devicetree@vger.kernel.org
Subject: Re: [PATCH 1/2] edac: sifive: Add DT documentation for SiFive L2 cache Controller
Date: Fri, 29 Mar 2019 14:41:05 -0500	[thread overview]
Message-ID: <CAL_JsqLQ1XvQq7L=xA5Z8Y0Xa4Bmp0t2pgxn+hLF+tD=_L7Mvg@mail.gmail.com> (raw)
In-Reply-To: <20190329142739.GG21152@zn.tnic>

On Fri, Mar 29, 2019 at 9:27 AM Borislav Petkov <bp@alien8.de> wrote:
>
> On Fri, Mar 29, 2019 at 09:11:24AM -0500, Rob Herring wrote:
> > I honestly don't understand the issue with EDAC is here.
>
> The EDAC core supports only one driver and if you need to load more, you
> need to dance around that.
>
> Also, if those drivers need to talk amongst each other, then they need
> to build something ad-hoc so that they can.
>
> And the other architectures can very well do one driver per platform -
> only ARM wants to do this special thing because DT said so. Or whatever.
>
> > Highbank is separate drivers for L2 ECC (PL310) and DDR. Both are used
> > on highbank.
>
> That's because your L2 driver does allocate an edac_device
> (edac_device_alloc_ctl_info()) and the DDR one an edac_mc
> (edac_mc_add_mc_with_groups).
>
> For example, altera_edac does edac_device_alloc_ctl_info() for each IP
> block just fine. So a single driver *can* work.
>
> > Only the DDR driver is used midway. (I think we never got around to
> > how to report A15 L2 ECC errors within Linux.)
> >
> > In any case, it's all irrelevant to the DT binding. We don't design
> > bindings around what some particular OS wants.
>
> And just because DT dictates one driver per IP block, I'm not going to
> redesign EDAC to fit that scheme. You or someone else who feels strongly
> about it, is more than welcome to do so, of course. And then maintain it
> too.

DT dictates aligning with what the h/w looks like which has little to
do with OS driver design. I never said you should change EDAC and I
outlined how things should be handled if it is one driver. DT and OS
subsystems are independent things. I can't tell you how to design the
subsystem and you can't dictate DT design (based on EDAC design).

Rob