dt-bindings: mmc: sprd: Add PHY DLL delay documentation

Introduce some PHY DLL delays properties to help to sample the PHY clock.
Signed-off-by: Baolin Wang <baolin.wang@linaro.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Documentation/devicetree/bindings/mmc/sdhci-sprd.txt

@@ -20,6 +20,23 @@ Optional properties:
 - assigned-clocks: the same with "sdio" clock
 - assigned-clock-parents: the default parent of "sdio" clock
 
+PHY DLL delays are used to delay the data valid window, and align the window
+to sampling clock. PHY DLL delays can be configured by following properties,
+and each property contains 4 cells which are used to configure the clock data
+write line delay value, clock read command line delay value, clock read data
+positive edge delay value and clock read data negative edge delay value.
+Each cell's delay value unit is cycle of the PHY clock.
+
+- sprd,phy-delay-legacy: Delay value for legacy timing.
+- sprd,phy-delay-sd-highspeed: Delay value for SD high-speed timing.
+- sprd,phy-delay-sd-uhs-sdr50: Delay value for SD UHS SDR50 timing.
+- sprd,phy-delay-sd-uhs-sdr104: Delay value for SD UHS SDR50 timing.
+- sprd,phy-delay-mmc-highspeed: Delay value for MMC high-speed timing.
+- sprd,phy-delay-mmc-ddr52: Delay value for MMC DDR52 timing.
+- sprd,phy-delay-mmc-hs200: Delay value for MMC HS200 timing.
+- sprd,phy-delay-mmc-hs400: Delay value for MMC HS400 timing.
+- sprd,phy-delay-mmc-hs400es: Delay value for MMC HS400 enhanced strobe timing.
+
 Examples:
 
 sdio0: sdio@20600000 {
@@ -33,6 +50,7 @@ sdio0: sdio@20600000 {
 	assigned-clocks = <&ap_clk CLK_EMMC_2X>;
 	assigned-clock-parents = <&rpll CLK_RPLL_390M>;
 
+	sprd,phy-delay-sd-uhs-sdr104 = <0x3f 0x7f 0x2e 0x2e>;
 	bus-width = <8>;
 	non-removable;
 	no-sdio;