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@xxxxxxxxxxxxx> > > > --- > > > .../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 -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
