[U-Boot] [PATCH 10/14] dm: mmc: sunxi: Add support for driver model

[Suneel Garapati]

Hi Simon,


On Fri, Jul 28, 2017 at 11:44 AM, Simon Glass <sjg at chromium.org> wrote:
> Hi Suneel,
>
> On 27 July 2017 at 23:03, Suneel Garapati <suneelglinux at gmail.com> wrote:
>> Hi Simon,
>>
>> I have similar requirement of Cavium boards using two card slots on
>> one host and currently trying to figure out to support it using
>> DM_MMC.
>> Would like to know if you have quick thoughts or seen similar use case
>> with some other boards too?
>
> It should work correctly - what sort of problem do you have?

Each mmc_bind call creates child blk_device and initialize the mmc
structure with defaults and further mmc_init or driver_probe would set
the rest of the members.
For the case, one host and two card slots, assuming card slots put up
as child nodes to mmc node in devicetree
     - driver probe called for once on host, initiates only one
mmc_bind call -> only one child blk device(udevice) created
     - also 'struct mmc' includes card specific data cid csd scr rca
which should scale for multiple slots simultaneously
     - assuming boot up detects two cards on two slots, mmc dev 0 will
chose host but not slot
     - mmc_uclass_priv holds mmc reference but depending on slot it
should get updated.
     - maybe need to split mmc into mmc_host and mmc_card structures like Linux.

Also, mmc dev 0/1 from cmd prompt would choose host and not the card slot.

Please correct me.

Regards,
Suneel

>
>>
>> Please correct me if I miss something obvious.
>>
>
> Regards,
> Simon
>
>> Regards,
>> Suneel
>>
>>
>> On Thu, Jul 27, 2017 at 9:19 PM, Simon Glass <sjg at chromium.org> wrote:
>>> Hi Maxime,
>>>
>>> On 17 July 2017 at 03:26, Maxime Ripard
>>> <maxime.ripard at free-electrons.com> wrote:
>>>> Hi Simon,
>>>>
>>>> On Fri, Jul 14, 2017 at 07:47:45AM -0600, Simon Glass wrote:
>>>>> On 5 July 2017 at 14:14, Maxime Ripard <maxime.ripard at free-electrons.com> wrote:
>>>>> > On Wed, Jul 05, 2017 at 04:57:40PM +0200, Maxime Ripard wrote:
>>>>> >> On Tue, Jul 04, 2017 at 01:33:25PM -0600, Simon Glass wrote:
>>>>> >> > Hi Maxime,
>>>>> >> >
>>>>> >> > On 21 June 2017 at 01:31, Maxime Ripard
>>>>> >> > <maxime.ripard at free-electrons.com> wrote:
>>>>> >> > > Hi Simon,
>>>>> >> > >
>>>>> >> > > On Mon, Jun 19, 2017 at 11:11:27AM -0600, Simon Glass wrote:
>>>>> >> > >> Add a driver-model version of this driver which mostly uses the existing
>>>>> >> > >> code. The old code can be removed once all boards are switched over.
>>>>> >> > >>
>>>>> >> > >> Signed-off-by: Simon Glass <sjg at chromium.org>
>>>>> >> > >
>>>>> >> > > I'm not sure if you tested that, but we have some code that switches
>>>>> >> > > the MMC indices when using both an eMMC and an external MMC.
>>>>> >> > >
>>>>> >> > > http://git.denx.de/?p=u-boot.git;a=blob;f=board/sunxi/board.c#l494
>>>>> >> > >
>>>>> >> > > This predates my time, but it seems that it was done to have a
>>>>> >> > > consistent boot MMC device ID.
>>>>> >> > >
>>>>> >> > > I'm not really sure we can get rid of it (even if it creates some
>>>>> >> > > issues of it's own), but what would be the impact of a switch to the
>>>>> >> > > device model on that logic?
>>>>> >> >
>>>>> >> > That is a pretty terrible hack.
>>>>> >>
>>>>> >> Yes, I know. This is especially bad when used together with other
>>>>> >> tools that rely on one MMC index for example (such as fastboot).
>>>>> >>
>>>>> >> I wanted to kill it for quite some time, but I'm a bit reluctant due
>>>>> >> to the possible side effects.
>>>>> >>
>>>>> >> > I'm not sure whether it will continue to work with DM. It does still
>>>>> >> > use the device number in the block device, so maybe...  Do you have
>>>>> >> > a board would use this?
>>>>> >>
>>>>> >> I guess I do. I'll give it a try or tonight and let you know.
>>>>> >
>>>>> > I just tested. Even with an eMMC (which was the first use case for
>>>>> > that hack), it works, even things that are not mainline yet (fastboot,
>>>>> > etc).
>>>>> >
>>>>> > It obviously break the old scripts relying on the mmc index, but I
>>>>> > guess that's ok.
>>>>> >
>>>>> > There's one regression though. Our eMMC will always be the second one,
>>>>> > which means that the distro bootargs will always boot on the external
>>>>> > SD first (which is always going to be mmc0).
>>>>> >
>>>>> > That's due to the fact that the eMMC controller is the third one, and
>>>>> > is thus probed last. We obviously want something deterministic for
>>>>> > fastboot for example, but booting partitions of the media you started
>>>>> > from make sense I guess. And this is what this hack was trying to
>>>>> > address.
>>>>>
>>>>> OK...so what should we do here?
>>>>
>>>> I guess we should just drop the hack. We'll have to at some point
>>>> anyway. But I guess we should also find a way to tweak the distro
>>>> bootcmd at boot time to search for the medium that we booted on first.
>>>>
>>>> I'm not really sure how to do this though.
>>>
>>> Well in that case let's drop the hack and someone will pick it up when
>>> it hits them.
>>>
>>> Regards,
>>> Simon
>>> _______________________________________________
>>> U-Boot mailing list
>>> U-Boot at lists.denx.de
>>> https://lists.denx.de/listinfo/u-boot