arm64: dts: qcom: db820c: Add vdd_gfx and tie it into mmcc

Add the SPMI regulator node in the PMI8994, use it to give us VDD_GX
at a fixed max nominal voltage for the db820c and specify this as supply
for the MMSS GPU_GX GDSC.

With the introduction of CPR support the range for VDD_GX should be
expanded.
Reviewed-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Rajendra Nayak <rnayak@codeaurora.org>
Link: https://lore.kernel.org/r/20200417070044.1376212-4-bjorn.andersson@linaro.org
[bjorn: Split between pmi8994 and db820c, changed voltage, rewrote commit message]
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

arch/arm64/boot/dts/qcom/apq8096-db820c.dtsi

@@ -241,6 +241,10 @@ &mdss {
 	status = "okay";
 };
 
+&mmcc {
+	vdd-gfx-supply = <&vdd_gfx>;
+};
+
 &msmgpio {
 	gpio-line-names =
 		"[SPI0_DOUT]", /* GPIO_0, BLSP1_SPI_MOSI, LSEC pin 14 */
@@ -678,6 +682,15 @@ pinconf {
 	};
 };
 
+&pmi8994_spmi_regulators {
+	vdd_gfx: s2@1700 {
+		reg = <0x1700 0x100>;
+		regulator-name = "VDD_GFX";
+		regulator-min-microvolt = <980000>;
+		regulator-max-microvolt = <980000>;
+	};
+};
+
 &rpm_requests {
 	pm8994-regulators {
 		compatible = "qcom,rpm-pm8994-regulators";

arch/arm64/boot/dts/qcom/pmi8994.dtsi

@@ -26,5 +26,11 @@ pmic@3 {
 		reg = <0x3 SPMI_USID>;
 		#address-cells = <1>;
 		#size-cells = <0>;
+
+		pmi8994_spmi_regulators: regulators {
+			compatible = "qcom,pmi8994-regulators";
+			#address-cells = <1>;
+			#size-cells = <1>;
+		};
 	};
 };