[RFC PATCH 0/4] Introduce new caps to improve the card's init sequence

Ulf Hansson ulf.hansson at linaro.org
Wed Jun 22 05:37:39 PDT 2016

On 8 June 2016 at 10:19, Shawn Lin <shawn.lin at rock-chips.com> wrote:
> Hi all,
> This patchset is gonna improve the card's init sequence
> by exposing some caps to DT.
> The basic idea is to skip sending specific init cmd inspired
> by Carlo Caione's commit[0].
> To make it possible, I firstly expose Carlo's MMC_CAP2_NO_SDIO
> to DT and extend two new caps for similar usage of sd and mmc.
> We probably need it because for most of the boards, each of the
> slots should have a specific function when designed. It's impossible
> for one slot which can either to be used as eMMC or a SD card for a
> given board. The same for SDIO case.
> We could have two ways to improve it
> A) Skip sending specific commands if knowing we don't support
> the specific card type.
> B) Allow sending specific commands if knowing we do support
> the specific card type.
> A) and B) shouldn't have difference, but I take A) as the final
> one as it looks more consistent with Carlo's way, which does not
> seem to break anything as possible.
> The only roadblock for this patchset to be landed should be the
> improvement we gain from it. Theoretically sdio-card doesn't get
> improvment as it's already in the first place to be attached.
> But considering the sd and (e)MMC case, we should gain more benifit
> from it.
> From the test, we can save nearly 2ms for attaching emmc against the
> original 8ms. And we gain more than 30us improvement for sd card for
> each insert.
> [0]: http://permalink.gmane.org/gmane.linux.kernel.mmc/34774
> Shawn Lin (4):
>   Documentation: mmc: add description for new caps
>   mmc: core: expose MMC_CAP2_NO_SDIO to dt-binding
>   mmc: core: add cap-no-sd and cap-no-mmc properties
>   mmc: core: improve initialization flow

I would prefer that you restructure this series a bit.

Start by adding each new MMC_CAP2* separately and without involving
the DT parsing.

Make the DT documentation patch come after the above, and add a new
separate patch which exposes the caps to device tree.

In that way, I can pick up the non DT parts and wait for Rob's
ack/nack of the DT bindings.

Kind regards

>  Documentation/devicetree/bindings/mmc/mmc.txt |  3 +++
>  drivers/mmc/core/core.c                       | 10 +++++-----
>  drivers/mmc/core/host.c                       |  6 ++++++
>  include/linux/mmc/host.h                      |  2 ++
>  4 files changed, 16 insertions(+), 5 deletions(-)
> --
> 2.3.7
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