[PATCH 2/3] mmc: Add OF bindings support for mmc host controller capabilities

[Thomas Abraham]

On 5 October 2011 21:25, Stephen Warren <swarren at nvidia.com> wrote:
> Thomas Abraham wrote at Wednesday, October 05, 2011 8:28 AM:
>> On 5 October 2011 18:59, Rob Herring <robherring2 at gmail.com> wrote:
>> > On 10/05/2011 05:13 AM, Thomas Abraham wrote:
>> >> Device nodes representing sd/mmc controllers in a device tree would include
>> >> mmc host controller capabilities. Add support for parsing of mmc host
>> >> controller capabilities included in device nodes.
> ...
>> >> +- linux,mmc_cap_4_bit_data - host can do 4 bit transfers
>> >> +- linux,mmc_cap_mmc_highspeed - host can do MMC high-speed timing
>> >> +- linux,mmc_cap_sd_highspeed - host can do SD high-speed timing
>> >> +- linux,mmc_cap_needs_poll - host needs polling for card detection
>> >> +- linux,mmc_cap_8_bit_data - host can do 8 bit transfer
>> >
>> > "sdhci,1-bit-only" already exists as a binding. Perhaps add
>> > "sdhci,4-bit-only". No property then means can do 8-bit.
>>
>> Ok. But that would remain just as sdhci host controller capability and
>> will not be applicable to other types of host controllers.
>
> Just as an FYI, NVIDIA's SDHCI controller bindings use property
> "support-8bit" to indicate 8-bit support. A similar property could be
> used for 4-bit support too.


In this case, the binding would be applicable only to nVidia's SDHCI
controller. And this binding would select MMC_CAP_8_BIT_DATA in the
sdhci-tegra driver. There are sdhci drivers that can accept host
capabilities via platform data.

The MMC_CAP_XXX macros in linux/mmc/host.h file are usuable across
host controllers and some of them are supplied as platform data for
non-device tree platforms.

So, bindings for MMC_CAP_XXX macros can be defined which any host
controller supporting device tree could use. Host controllers could
use the mmc_of_parse_host_caps() helper function (listed in this
patch) to parse all the bindings for MMC_CAP_XXX  available in the
device node.

I would like to retain this patch in this series but if there is a
definite no, then I will drop it. Please let me know your opinion.

Thanks,
Thomas.

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