ARM: imx: add standby mode support for suspend

Add standby mode support for suspend, to enter standby mode:

echo standby > /sys/power/state;

Use UART or RTC alarm to wake up system, when system enters
standby mode, SOC will enter STOP mode with ARM core kept
power on and 24M XTAL on.
Signed-off-by: NAnson Huang <b20788@freescale.com>
Signed-off-by: NShawn Guo <shawn.guo@freescale.com>

arch/arm/mach-imx/common.h

@@ -106,7 +106,7 @@ static inline void imx_scu_standby_enable(void) {}
 #endif
 void imx_src_init(void);
 void imx_gpc_init(void);
-void imx_gpc_pre_suspend(void);
+void imx_gpc_pre_suspend(bool arm_power_off);
 void imx_gpc_post_resume(void);
 void imx_gpc_mask_all(void);
 void imx_gpc_restore_all(void);

arch/arm/mach-imx/gpc.c

@@ -27,13 +27,14 @@ static void __iomem *gpc_base;
 static u32 gpc_wake_irqs[IMR_NUM];
 static u32 gpc_saved_imrs[IMR_NUM];
 
-void imx_gpc_pre_suspend(void)
+void imx_gpc_pre_suspend(bool arm_power_off)
 {
 	void __iomem *reg_imr1 = gpc_base + GPC_IMR1;
 	int i;
 
 	/* Tell GPC to power off ARM core when suspend */
-	writel_relaxed(0x1, gpc_base + GPC_PGC_CPU_PDN);
+	if (arm_power_off)
+		writel_relaxed(0x1, gpc_base + GPC_PGC_CPU_PDN);
 
 	for (i = 0; i < IMR_NUM; i++) {
 		gpc_saved_imrs[i] = readl_relaxed(reg_imr1 + i * 4);

arch/arm/mach-imx/pm-imx6.c

@@ -274,6 +274,14 @@ int imx6q_set_lpm(enum mxc_cpu_pwr_mode mode)
 		break;
 	case STOP_POWER_ON:
 		val |= 0x2 << BP_CLPCR_LPM;
+		val &= ~BM_CLPCR_VSTBY;
+		val &= ~BM_CLPCR_SBYOS;
+		if (cpu_is_imx6sl())
+			val |= BM_CLPCR_BYPASS_PMIC_READY;
+		if (cpu_is_imx6sl() || cpu_is_imx6sx())
+			val |= BM_CLPCR_BYP_MMDC_CH0_LPM_HS;
+		else
+			val |= BM_CLPCR_BYP_MMDC_CH1_LPM_HS;
 		break;
 	case WAIT_UNCLOCKED_POWER_OFF:
 		val |= 0x1 << BP_CLPCR_LPM;
@@ -334,6 +342,19 @@ static int imx6q_suspend_finish(unsigned long val)
 static int imx6q_pm_enter(suspend_state_t state)
 {
 	switch (state) {
+	case PM_SUSPEND_STANDBY:
+		imx6q_set_lpm(STOP_POWER_ON);
+		imx6q_set_int_mem_clk_lpm(true);
+		imx_gpc_pre_suspend(false);
+		if (cpu_is_imx6sl())
+			imx6sl_set_wait_clk(true);
+		/* Zzz ... */
+		cpu_do_idle();
+		if (cpu_is_imx6sl())
+			imx6sl_set_wait_clk(false);
+		imx_gpc_post_resume();
+		imx6q_set_lpm(WAIT_CLOCKED);
+		break;
 	case PM_SUSPEND_MEM:
 		imx6q_set_lpm(STOP_POWER_OFF);
 		imx6q_set_int_mem_clk_lpm(false);
@@ -344,7 +365,7 @@ static int imx6q_pm_enter(suspend_state_t state)
 		 */
 		if (!imx6_suspend_in_ocram_fn)
 			imx6q_enable_rbc(true);
-		imx_gpc_pre_suspend();
+		imx_gpc_pre_suspend(true);
 		imx_anatop_pre_suspend();
 		imx_set_cpu_jump(0, v7_cpu_resume);
 		/* Zzz ... */
@@ -365,9 +386,14 @@ static int imx6q_pm_enter(suspend_state_t state)
 	return 0;
 }
 
+static int imx6q_pm_valid(suspend_state_t state)
+{
+	return (state == PM_SUSPEND_STANDBY || state == PM_SUSPEND_MEM);
+}
+
 static const struct platform_suspend_ops imx6q_pm_ops = {
 	.enter = imx6q_pm_enter,
-	.valid = suspend_valid_only_mem,
+	.valid = imx6q_pm_valid,
 };
 
 void __init imx6q_pm_set_ccm_base(void __iomem *base)