Re: [PATCH V4] ARM: dts: Add dwmmc DT nodes for exynos5420 SOC

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On Tue, Aug 27, 2013 at 01:02:52PM +0100, Yuvaraj Kumar wrote:
> On Tue, Aug 27, 2013 at 4:31 PM, Mark Rutland <mark.rutland@xxxxxxx> wrote:
> > On Tue, Aug 27, 2013 at 10:22:31AM +0100, Yuvaraj Kumar C D wrote:
> >> This patch adds the device tree node entries for exynos5420 SOC.
> >> Exynos5420 has a different version of DWMMC controller,so a new
> >> compatible string is used to distinguish it from the prior SOC's.
> >>
> >> This patch depends on
> >>       mmc: dw_mmc: exynos: Add a new compatible string for exynos5420
> >>
> >> changes since V3:
> >>       1.change fifo-depth size from 0x80 to 0x40
> >>       2.Move the below properties
> >>               a.card-detect-delay
> >>               b.samsung,dw-mshc-ciu-div
> >>               c.samsung,dw-mshc-sdr-timing
> >>               d.samsung,dw-mshc-ddr-timing
> >>       from SOC dts to board dts file as suggested by Doug Anderson
> >>
> >> changes since V2:
> >>       1.dropped num-slots property from node as its not required
> >>         if number of card slots available is 1.
> >>
> >>       2.Move the below properties
> >>               a.fifo-depth
> >>               b.card-detect-delay
> >>               c.samsung,dw-mshc-ciu-div
> >>               d.samsung,dw-mshc-sdr-timing
> >>               e.samsung,dw-mshc-ddr-timing
> >>       from board dts to SOC dts,as these are not board specific properties.
> >>
> >>       3.Updated the binding document exynos-dw-mshc.txt.
> >>
> >> changes since V1:
> >>       1.disable node by status = disabled in SOC file
> >>       2.enable node by status = okay in board specific file
> >>
> >> Signed-off-by: Yuvaraj Kumar C D <yuvaraj.cd@xxxxxxxxxxx>
> >> ---
> >>  .../devicetree/bindings/mmc/exynos-dw-mshc.txt     |    4 ++
> >>  arch/arm/boot/dts/exynos5420-smdk5420.dts          |   34 +++++++++++++++++
> >>  arch/arm/boot/dts/exynos5420.dtsi                  |   39 ++++++++++++++++++++
> >>  3 files changed, 77 insertions(+)
> >>
> >> diff --git a/Documentation/devicetree/bindings/mmc/exynos-dw-mshc.txt b/Documentation/devicetree/bindings/mmc/exynos-dw-mshc.txt
> >> index 6d1c098..25368e8 100644
> >> --- a/Documentation/devicetree/bindings/mmc/exynos-dw-mshc.txt
> >> +++ b/Documentation/devicetree/bindings/mmc/exynos-dw-mshc.txt
> >> @@ -16,6 +16,8 @@ Required Properties:
> >>         specific extensions.
> >>       - "samsung,exynos5250-dw-mshc": for controllers with Samsung Exynos5250
> >>         specific extensions.
> >> +     - "samsung,exynos5420-dw-mshc": for controllers with Samsung Exynos5420
> >> +       specific extensions.
> >>
> >>  * samsung,dw-mshc-ciu-div: Specifies the divider value for the card interface
> >>    unit (ciu) clock. This property is applicable only for Exynos5 SoC's and
> >> @@ -31,6 +33,8 @@ Required Properties:
> >>    data rate mode operation. Refer notes below for the order of the cells and the
> >>    valid values.
> >>
> >> +* bypass-smu: Bypass Security Management Unit of eMMC channel 0 and channel 1.
> >> +
> >
> > Could you elaborate on why this is needed?
> Exynos5420  Mobile Storage Host controller has a Security Management
> Unit (SMU) for
> channel 0 and channel 1 (mainly for eMMC). This binding property
> requires to add a quirk
> to bypass SMU as it is not being used yet.

When you say it's not being used _yet_, what do you mean? That the
driver doesn't have support for it, but will in future?

Can the driver not just choose to bypass it entirely for now, regardless
of what's in the dt? Do we need to bypass it in future for some reason?

I don't see why this needs to be in the dt.

> >
> > Is the SMU broken or not present in some hardware revisions?
> SMU is only present in channel 0 and channel 1,but not in channel 2.So
> to distinguish this,
> bypass-smu property has been added as quirks in the channel.
> >
> >>    Notes for the sdr-timing and ddr-timing values:
> >>
> >>      The order of the cells should be
> >
> > On an unrelated note, I see the binding in mainline defines a gpios
> > property that doesn't seem to be used anywhere. Am I missing something,
> > or do we just not have support for that part of the binding?
> Yes,This document has been little outdated.I will update and post a
> separate patch.

Cheers!

Mark.
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