[PATCH v2 5/8] mmc: sdhci-esdhc-imx: add delay line setting support

[Shawn Guo]

On Fri, Oct 18, 2013 at 07:30:47PM +0800, Dong Aisheng wrote:
> On Fri, Oct 18, 2013 at 07:42:35PM +0800, Shawn Guo wrote:
> > On Fri, Oct 18, 2013 at 06:54:18PM +0800, Dong Aisheng wrote:
> > > The DLL(Delay Line) is newly added to assist in sampling read data.
> > > The DLL provides the ability to programmatically select a quantized
> > > delay (in fractions of the clock period) regardless of on-chip variations
> > > such as process, voltage and temperature (PVT).
> > > 
> > > This patch adds a user interface to set slave delay line via device tree.
> > > It's usually used in high speed mode like mmc DDR mode when the signal
> > > quality is not good caused by board design, e.g. the signal path is too long.
> > > User can manual set delay line to find a suitable data sampling window
> > > for card to work properly.
> > > 
> > > Signed-off-by: Dong Aisheng <b29396 at freescale.com>
> > > ---
> > >  .../devicetree/bindings/mmc/fsl-imx-esdhc.txt      |    5 +++++
> > >  drivers/mmc/host/sdhci-esdhc-imx.c                 |   18 ++++++++++++++++++
> > >  include/linux/platform_data/mmc-esdhc-imx.h        |    1 +
> > >  3 files changed, 24 insertions(+), 0 deletions(-)
> > > 
> > > diff --git a/Documentation/devicetree/bindings/mmc/fsl-imx-esdhc.txt b/Documentation/devicetree/bindings/mmc/fsl-imx-esdhc.txt
> > > index 1dd6225..78a45c5 100644
> > > --- a/Documentation/devicetree/bindings/mmc/fsl-imx-esdhc.txt
> > > +++ b/Documentation/devicetree/bindings/mmc/fsl-imx-esdhc.txt
> > > @@ -12,6 +12,11 @@ Required properties:
> > >  Optional properties:
> > >  - fsl,cd-controller : Indicate to use controller internal card detection
> > >  - fsl,wp-controller : Indicate to use controller internal write protection
> > > +- fsl,delay-line : Specify the number of delay cells for override mode.
> > > +  This is used to set the clock delay for DLL(Delay Line) on override mode
> > > +  to select a proper data sampling window in case the clock quality is not good
> > > +  due to signal path is too long on the board.
> > > +  please refer to DLL chapter in RM for details.
> > 
> > It might be better to reword it like:
> > 
> > Please refer to eSDHC/uSDHC DLL_CTRL register bit field
> > DLL_CTRL_SLV_OVERRIDE_VAL in Reference Manual for details.
> > 
> 
> There is a DLL (Delay Line) chapter in the reference manual which
> has more detailed descriptions on the delay line including override mode.
> So i think it may be better to point user to the DLL chapter for understanding,
> then naturally user will refer to register for bit defines later too.
> Does it make sense?

Okay.  But "eSDHC/uSDHC chapter, DLL (Delay Line) section" please.

Shawn