RE: [v4, 5/6] mmc: kconfig: select FSL_GUTS for MMC_SDHCI_OF_ESDHC

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> -----Original Message-----
> From: Scott Wood [mailto:scottwood@xxxxxxxxxxxxx]
> Sent: Tuesday, December 29, 2015 3:10 AM
> To: Ulf Hansson; Yangbo Lu
> Cc: Lu Yangbo-B47093; linux-mmc; Xie Xiaobo-R63061; Leo li
> Subject: Re: [v4, 5/6] mmc: kconfig: select FSL_GUTS for
> MMC_SDHCI_OF_ESDHC
> 
> On Mon, 2015-12-28 at 13:10 +0100, Ulf Hansson wrote:
> > On 28 December 2015 at 11:26, Yangbo Lu <yangbo.lu@xxxxxxx> wrote:
> > > > -----Original Message-----
> > > > From: Ulf Hansson [mailto:ulf.hansson@xxxxxxxxxx]
> > > > Sent: Thursday, December 17, 2015 7:31 PM
> > > > To: Scott Wood
> > > > Cc: Lu Yangbo-B47093; linux-mmc; Xie Xiaobo-R63061; Leo li
> > > > Subject: Re: [v4, 5/6] mmc: kconfig: select FSL_GUTS for
> > > > MMC_SDHCI_OF_ESDHC
> > > >
> > > > [...]
> > > >
> > > > > >
> > > > > > And I think stubs for reading SVR is quite a bad idea.  It'll
> > > > > > make the driver build but it will silently not be able to
> > > > > > apply SVR-based
> > > > workarounds.
> > > > >
> > > > > It doesn't have to be "silent", the driver can return an error
> > > > > (and print error messages) from its ->probe() method, if the
> > > > > calls to the GUTS driver fails.
> > > > >
> > > > > Anyway, I mentioned this idea only to understand the need for
> > > > > *optional* GUTS supports. Perhaps there is a cross SOC drivers
> > > > > that for some platforms depends on GUTS but on others it doesn't.
> > > > >
> > > > > Maybe that isn't case then!?
> > > >
> > > > Can you please answer this question!?
> > > >
> > > > According to the earlier versions of this patchset and from your
> > > > comments [1], it *do* seems like the GUTS driver may be optional
> > > > and thus stubs could address this.
> > > >
> > > > Kind regards
> > > > Uffe
> > > >
> > > > [1]
> > > > http://www.spinics.net/lists/linux-mmc/msg34412.html
> > >
> > > [Lu Yangbo-B47093] Hi Scott and Uffe, In the earlier version, I'd
> > > like to use syscon support and only add 'syscon' compatible in the
> > > dts whose eSDHC needs to use it to get SVR.
> > > But I never thought this had caused so much discussion... :(
> >
> > Sorry, I understand your frustration but that's life sometimes. :-)
> >
> > To me, the syscon solution is more elegant...
> 
> The syscon patch was terrible.  It would have accessed a certain location
> in any node labelled "syscon" whether it was guts or not, in addition to
> the other complaints.
> 
> -Scott

[Lu Yangbo-B47093] As my understand, the syscon APIs would just check whether there is a 'syscon' compatible.
If no, the APIs return. We still could maintain a list of compatibles for guts if using syscon.
In my opinion, syscon and guts driver are just two method to get SVR.

I agree with Uffe, because I think syscon is really designed for this situation and many arm platforms are using it.
Of course, I still would like to try guts driver if you insist on it.






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