Re: [PATCH v3 06/13] mmc: tmio-mmc: define device-tree bindings

On Wed, Feb 06, 2013 at 10:24:20PM +0000, Arnd Bergmann wrote:

On Wednesday 06 February 2013, Guennadi Liakhovetski wrote:

quoted

+* Toshiba Mobile IO SD/MMC controller
+
+The tmio-mmc driver doesn't probe its devices actively, instead its binding to
+devices is managed by either MFD drivers or by the sh_mobile_sdhi platform
+driver. Those drivers supply the tmio-mmc driver with platform data, that either
+describe hardware capabilities, known to them, or are obtained by them from
+their own platform data or from their DT information. In the latter case all
+compulsory and any optional properties, common to all SD/MMC drivers, as
+described in mmc.txt, should or can be used. Additionally the following optional
+bindings can be used. They set respective TMIO_MMC_* flags.
+
+Optional properties:
+- toshiba,mmc-wrprotect-disable        : set TMIO_MMC_WRPROTECT_DISABLE flag
+- toshiba,mmc-blksz-2bytes     : set TMIO_MMC_BLKSZ_2BYTES
+- toshiba,mmc-has-idle-wait    : set TMIO_MMC_HAS_IDLE_WAIT

Please write the binding in a way that does not refer to a specific
implementation in Linux: The binding should describe the hardware
independent of details in the driver. In particular, I think you
should not refer to the TMIO_MMC_BLKSZ_2BYTES etc macros but describe
in text what the flags are about.

Regarding the toshiba,mmc-wrprotect-disable property, would it be
enough to just check the presence of the wp-gpios property?

TMIO_MMC_BLKSZ_2BYTES seems to be set unconditionally in
sh_mobile_sdhi_probe and nowhere else, so I'd assume we don't
actually need to provide this here, but can keep that knowledge
implicit based on whether we're talking to sh_mobile_sdhi
or another tmio_mmc variant.

For the other last one, is that actually board specific, or just
a feature of a given chip? If we can tell by the SoC, then I'd
suggest using separate "compatible" properties instead, and
put a bitmask of features into the .data field of the of match
table. For all I can tell, SH7372 does not set it, while SH73A0,
R8A7740 and R8A7779 always do.

My understanding is that TMIO_MMC_HAS_IDLE_WAIT can be set based
on the SoC in use.