[PATCH 3/3] mmc: sdhci-of-esdhc: add workaround for T4240 incorrect HOSTVER value

[Scott Wood]

On Mon, 2015-07-27 at 09:58 +0200, Ulf Hansson wrote:
> On 25 July 2015 at 04:27, Scott Wood <scottwood at freescale.com> wrote:
> > On Tue, 2015-07-21 at 15:02 +0200, Ulf Hansson wrote:
> > > On 21 July 2015 at 11:45, Yangbo Lu <yangbo.lu at freescale.com> wrote:
> > > > For T4240-R1.0-R2.0, the HOSTVER register has incorrcet vender
> > > > version value and sdhc spec version value. This will break down
> > > > the ADMA data transfer. So add workaround to get right value
> > > > VVN=0x13, SVN = 0x1.
> > > 
> > > So T4240-R1.0-R2.0 is the version of the controller, right?
> > > 
> > > If I understand correct you are checking what CPU/SoC you are running
> > > on, to figure out which controller version you are using, as that
> > > can't be fetched (trusted) from the registers of the esdhc controller
> > > itself!?
> > > 
> > > Instead, you could deal with this directly in the DTS files. I assume
> > > you have some DTS file for each SoC/board variant, right?
> > 
> > No, we do not 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 principle, in your DTS file specific for the board/SoC that holds
> > > the T4240-R1.0-R2.0 version of the controller, should add a specific
> > > esdhc DT property to indicate this errata.
> > 
> > No, because (in addition to the above issue about chip revisions) the 
> > device
> > tree is stable ABI and errata are often discovered after device trees are
> > deployed.
> 
> Fair enough. Then what is your suggestion for the solution here?

As I said in my comment on patch 2/3, read SVR from the device-config/guts 
MMIO block, which works on both PPC and ARM.

-Scott