From: Arnd Bergmann <arnd@arndb.de>
To: Rob Herring <robh@kernel.org>
Cc: Scott Wood <scott.wood@nxp.com>, Yangbo Lu <yangbo.lu@nxp.com>,
        "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>,
        "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
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        Zhao Qiang <qiang.zhao@freescale.com>,
        Russell King <linux@arm.linux.org.uk>,
        Bhupesh Sharma <bhupesh.sharma@freescale.com>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        Joerg Roedel <joro@8bytes.org>, Kumar Gala <galak@codeaurora.org>,
        "linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Yang-Leo Li <leoyang.li@nxp.com>,
        "iommu@lists.linux-foundation.org" <iommu@lists.linux-foundation.org>,
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        Claudiu Manoil <claudiu.manoil@freescale.com>,
        Santosh Shilimkar <ssantosh@kernel.org>,
        Xiaobo Xie <xiaobo.xie@nxp.com>,
        "linux-clk@vger.kernel.org" <linux-clk@vger.kernel.org>,
        "linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>
Subject: Re: [v6, 5/5] mmc: sdhci-of-esdhc: fix host version for T4240-R1.0-R2.0
Date: Thu, 17 Mar 2016 18:06:09 +0100
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On Thursday 17 March 2016 12:01:01 Rob Herring wrote:
> On Mon, Mar 14, 2016 at 05:45:43PM +0000, Scott Wood wrote:

> > >> This makes the driver non-portable. Better identify the specific
> > >> workarounds based on the compatible string for this device, or add a
> > >> boolean DT property for the quirk.
> > >>
> > >>    Arnd
> > > 
> > > [Lu Yangbo-B47093] Hi Arnd, we did have a discussion about using DTS in v1 before.
> > > https://patchwork.kernel.org/patch/6834221/
> > > 
> > > We don’t have a separate DTS file for each revision of an SOC and if we did, we'd constantly have people using the wrong one.
> > > In addition, the device tree is stable ABI and errata are often discovered after device tree are deployed.
> > > See the link for details.
> > > 
> > > So we decide to read SVR from the device-config/guts MMIO block other than using DTS.
> > > Thanks.
> > 
> > Also note that this driver is already only for fsl-specific hardware,
> > and it will still work even if fsl_guts doesn't find anything to bind to
> > -- it just wouldn't be able to detect errata based on SVR in that case.
> 
> IIRC, it is the same IP block as i.MX and Arnd's point is this won't 
> even compile on !PPC. It is things like this that prevent sharing the 
> driver.

I think the first four patches take care of building for ARM,
but the problem remains if you want to enable COMPILE_TEST as
we need for certain automated checking.

> Dealing with Si revs is a common problem. We should have a 
> common solution. There is soc_device for this purpose.

Exactly. The last time this came up, I think we agreed to implement a
helper using glob_match() on the soc_device strings. Unfortunately
this hasn't happened then, but I'd still prefer that over yet another
vendor-specific way of dealing with the generic issue.

	Arnd