linux-kernel - Re: [RFC PATCH 0/4] Introduce new caps to improve the card's init sequence

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Message-ID: <CAPDyKFp+ugPtHsxa1O9eeArkJjoM2sL2F7gqAekgus1qoi3UUw@mail.gmail.com>
Date:	Wed, 22 Jun 2016 14:37:39 +0200
From:	Ulf Hansson <ulf.hansson@...aro.org>
To:	Shawn Lin <shawn.lin@...k-chips.com>
Cc:	Jaehoon Chung <jh80.chung@...sung.com>,
	Rob Herring <robh+dt@...nel.org>,
	linux-mmc <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Doug Anderson <dianders@...omium.org>,
	"open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [RFC PATCH 0/4] Introduce new caps to improve the card's init sequence

On 8 June 2016 at 10:19, Shawn Lin <shawn.lin@...k-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
Uffe

>  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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