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linux-next/Documentation/devicetree/bindings/mmc/fsl-imx-esdhc.txt
Dong Aisheng 602519b2bd mmc: sdhci-esdhc-imx: add delay line setting support
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 manually set delay line to find a suitable data sampling
window for card to work properly.

Signed-off-by: Dong Aisheng <b29396@freescale.com>
Acked-by: Shawn Guo <shawn.guo@linaro.org>
Signed-off-by: Chris Ball <cjb@laptop.org>
2013-10-21 15:58:13 -04:00

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* Freescale Enhanced Secure Digital Host Controller (eSDHC) for i.MX
The Enhanced Secure Digital Host Controller on Freescale i.MX family
provides an interface for MMC, SD, and SDIO types of memory cards.
This file documents differences between the core properties described
by mmc.txt and the properties used by the sdhci-esdhc-imx driver.
Required properties:
- compatible : Should be "fsl,<chip>-esdhc"
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 eSDHC/uSDHC
chapter, DLL (Delay Line) section in RM for details.
Examples:
esdhc@70004000 {
compatible = "fsl,imx51-esdhc";
reg = <0x70004000 0x4000>;
interrupts = <1>;
fsl,cd-controller;
fsl,wp-controller;
};
esdhc@70008000 {
compatible = "fsl,imx51-esdhc";
reg = <0x70008000 0x4000>;
interrupts = <2>;
cd-gpios = <&gpio1 6 0>; /* GPIO1_6 */
wp-gpios = <&gpio1 5 0>; /* GPIO1_5 */
};