imx: mx7: psci: add system power off support

Add i.MX7 PSCI system power off support, linux
kernel can use "poweroff" command to power off
system via SNVS, PMIC power will be disabled.
Signed-off-by: NAnson Huang <Anson.Huang@nxp.com>

arch/arm/mach-imx/mx7/psci-mx7.c

@@ -26,6 +26,12 @@
 #define BP_SRC_A7RCR0_A7_CORE_RESET0	0
 #define BP_SRC_A7RCR1_A7_CORE1_ENABLE	1
 
+#define SNVS_LPCR		0x38
+#define BP_SNVS_LPCR_DP_EN	0x20
+#define BP_SNVS_LPCR_TOP	0x40
+
+#define CCM_CCGR_SNVS		0x4250
+
 #define CCM_ROOT_WDOG		0xbb80
 #define CCM_CCGR_WDOG1		0x49c0
 
@@ -87,3 +93,15 @@ __secure void imx_system_reset(void)
 	writel(0x3, CCM_BASE_ADDR + CCM_CCGR_WDOG1);
 	writew(WCR_WDE, &wdog->wcr);
 }
+
+__secure void imx_system_off(void)
+{
+	u32 val;
+
+	/* make sure SNVS clock is enabled */
+	writel(0x3, CCM_BASE_ADDR + CCM_CCGR_SNVS);
+
+	val = readl(SNVS_BASE_ADDR + SNVS_LPCR);
+	val |= BP_SNVS_LPCR_DP_EN | BP_SNVS_LPCR_TOP;
+	writel(val, SNVS_BASE_ADDR + SNVS_LPCR);
+}

arch/arm/mach-imx/mx7/psci.S

@@ -50,4 +50,11 @@ psci_system_reset:
 2: 	wfi
 	b 2b
 
+.globl psci_system_off
+psci_system_off:
+	bl	imx_system_off
+
+3: 	wfi
+	b 3b
+
 	.popsection