SD card driver for Freescale i.MX6 in Genode

[Martin Stein]

Hi Praveen, Norman,

First of all, it's cool to see you sharing this code with us and I
enjoyed reading it!

According to the i.MX6 manual, the uSDHC is a new implementation that is
at least not fully compatible with the eSDHC. For example, there are new
registers, new features (tuning), and common registers differ. I think
it's a good idea to treat uSDHC and eSDHC separately for now and maybe
later determine in which way they can share more code.

Regarding your commit, Praveen, there are two suggestions that came to
my mind while having a first look at it:

* I saw that you've opened up a new sd_card.h in the uSDHC sub-directory
of the driver. However, the concept of the existing generic sd_card.h is
to provide SD-card functionality that is independent of the specific
hardware implementation. Thus, if the code you've added in
usdhc/sd_card.h is of such characteristic, I would suggest to provide it
through the existing sd_card.h instead of adding a new header. If the
existing implementations in sd_card.h are not sufficient to reuse them
properly for the uSDHC, they should rather be adapted.

* For sources you've added around the driver like
    repos/ports-foc/run/linux_imx6.run
    repos/os/run/part_blk_sd.run
    repos/dde_rump/run/rump_ext2_sd.run
I would create dedicated commits so the driver commit really
concentrates on the driver and its dependencies. This way, one can add
and test this feature without the need for fetching such sattelite code.

Beside that, the code looks clean and comprehensible to me :)

Best regards,
Martin


On 20.03.2015 11:40, Norman Feske wrote:
> Hello Praveen,
>
>> We have developed a Genode device driver for USDHC card reader for
>> Freescale i.MX6 procesor.
>>
>> You may find the corresponding code in the repository,
>> https://github.com/srinivasprv/genode 
>>
>> The specific driver code is available in usdhc directory of sd_card
>> directory.
> thank you for sharing your work with us! Your patch looks very nice.
> Coincidentally, we just added an SD-card driver for the i.MX53 platform
> last week. See the following commit referenced at the following issue:
>
>   https://github.com/genodelabs/genode/issues/1458
>
> Whereas the i.MX53 driver addresses the so-called ESDHC controller, your
> patch addresses the USDHC controller. Are both drivers complementary?
>
> On another note, the mainline Genode version does not officially support
> i.MX6 yet. So I am afraid that including your driver without prior
> enabling i.MX6 would not be very sensible. As a precondition, we should
> enable at least one i.MX6-based platform (e.g., Wandboard?). Otherwise,
> we would not able to add your driver to our regular test infrastructure.
> What do you think about how to go about it?
>
> Best regards
> Norman
>