dt-bindings: mmc: add description of PHY delays for sdhci-cadence

DTS properties are used instead of fixed data
because PHY settings can be different for different chips/boards.
Add description of new DLL PHY delays.
Signed-off-by: Piotr Sroka <piotrs@cadence.com>
Reviewed-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

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

@@ -19,6 +19,53 @@ if supported.  See mmc.txt for details.
 - mmc-hs400-1_8v
 - mmc-hs400-1_2v
 
+Some PHY delays can be configured by following properties.
+PHY DLL input delays:
+They are used to delay the data valid window, and align the window
+to sampling clock. The delay starts from 5ns (for delay parameter equal to 0)
+and it is increased by 2.5ns in each step.
+- cdns,phy-input-delay-sd-highspeed:
+  Value of the delay in the input path for SD high-speed timing
+  Valid range = [0:0x1F].
+- cdns,phy-input-delay-legacy:
+  Value of the delay in the input path for legacy timing
+  Valid range = [0:0x1F].
+- cdns,phy-input-delay-sd-uhs-sdr12:
+  Value of the delay in the input path for SD UHS SDR12 timing
+  Valid range = [0:0x1F].
+- cdns,phy-input-delay-sd-uhs-sdr25:
+  Value of the delay in the input path for SD UHS SDR25 timing
+  Valid range = [0:0x1F].
+- cdns,phy-input-delay-sd-uhs-sdr50:
+  Value of the delay in the input path for SD UHS SDR50 timing
+  Valid range = [0:0x1F].
+- cdns,phy-input-delay-sd-uhs-ddr50:
+  Value of the delay in the input path for SD UHS DDR50 timing
+  Valid range = [0:0x1F].
+- cdns,phy-input-delay-mmc-highspeed:
+  Value of the delay in the input path for MMC high-speed timing
+  Valid range = [0:0x1F].
+- cdns,phy-input-delay-mmc-ddr:
+  Value of the delay in the input path for eMMC high-speed DDR timing
+  Valid range = [0:0x1F].
+
+PHY DLL clock delays:
+Each delay property represents the fraction of the clock period.
+The approximate delay value will be
+(<delay property value>/128)*sdmclk_clock_period.
+- cdns,phy-dll-delay-sdclk:
+  Value of the delay introduced on the sdclk output
+  for all modes except HS200, HS400 and HS400_ES.
+  Valid range = [0:0x7F].
+- cdns,phy-dll-delay-sdclk-hsmmc:
+  Value of the delay introduced on the sdclk output
+  for HS200, HS400 and HS400_ES speed modes.
+  Valid range = [0:0x7F].
+- cdns,phy-dll-delay-strobe:
+  Value of the delay introduced on the dat_strobe input
+  used in HS400 / HS400_ES speed modes.
+  Valid range = [0:0x7F].
+
 Example:
 	emmc: sdhci@5a000000 {
 		compatible = "socionext,uniphier-sd4hc", "cdns,sd4hc";
@@ -29,4 +76,5 @@ Example:
 		mmc-ddr-1_8v;
 		mmc-hs200-1_8v;
 		mmc-hs400-1_8v;
+		cdns,phy-dll-delay-sdclk = <0>;
 	};