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From: Marek Vasut <marek.vasut@gmail.com>
To: Dong Aisheng <aisheng.dong@freescale.com>
Subject: Re: [PATCH v1 2/5] mmc: mxs-mmc: add dt probe support
Date: Wed, 14 Mar 2012 12:17:19 +0100
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Dear Dong Aisheng,

> On Wed, Mar 14, 2012 at 08:09:22AM +0100, Marek Vasut wrote:
> > Dear Dong Aisheng,
> > 
> > > On Wed, Mar 14, 2012 at 01:58:25PM +0800, Marek Vasut wrote:
> > > > Dear Dong Aisheng,
> > > > 
> > > > > Signed-off-by: Dong Aisheng <dong.aisheng@linaro.org>
> > > 
> > > ........
> > > 
> > > > > +static const struct of_device_id mxs_mmc_dt_ids[] = {
> > > > > +	{ .compatible = "fsl,imx23-mmc", .data = NULL, },
> > > > > +	{ .compatible = "fsl,imx28-mmc", .data = NULL, },
> > > > 
> > > > Do you really need two distinct ones here?
> > > 
> > > Hmm, my original purpose is to put soc difference data in .data
> > > to remove cpu_is_* function calls in the driver later.
> > > Do you think if any issue?
> > 
> > Well, what's the difference between the interfaces on mx233 and mx28? Is
> > it something that can't be encoded otherwise? I think they're not so
> > different.
> 
> Not much difference except the one register offset and ip version.
> See:
> #define SSP_VERSION_LATEST      4
> #define ssp_is_old()            (host->version < SSP_VERSION_LATEST)
> ..
> #define HW_SSP_VERSION (cpu_is_mx23() ? 0x110 : 0x130)
> The ip version can be handled in driver, but for offset...
> it depends on cpu_is_* macro.
> Putting the HW_SSP_VERSION offset difference in .data can eliminate the
> need of cpu_is_*.
> 
> Despite of that, since they're two devices,
> i guess it's ok to put two compatible string there, right?
> Or you thought just put one as below?
> { .compatible = "fsl,mxs-mmc", .data = NULL, },
> 
No, I understand now /wrt the register layout.

Best regards,
Marek Vasut