ARM: imx6: initialize CCM_CLPCR_LPM into RUN mode earlier

Commit 4631960d26da ("ARM: imx6: set initial power mode in pm function")
moves imx6_set_lpm() from clock init function into
imx6_pm_common_init().  This causes a hang when cpuidle support is
enabled.  The reason for that is ARM core clock is shut down
unexpectedly by WAIT mode.  It happens with the following call stack:

    cpuidle_register_governor()
        cpuidle_switch_governor()
            cpuidle_uninstall_idle_handler()
                synchronize_sched()
                    wait_rcu_gp()
                        wait_for_completion()

When wait_for_completion() is called as above, all cores are idle/WFI.
Hence, the reset value of CCM_CLPCR_LPM - WAIT mode, will trigger a
hardware shutdown of the ARM core clock.

To fix the regression, we need to ensure that CCM_CLPCR_LPM is
initialized into RUN mode earlier than cpuidle governor registration,
which is a postcore_initcall.  This patch creates function
imx6_pm_ccm_init() to map CCM block and initialize CCM_CLPCR_LPM into
RUN mode, and have the function called from machine .init_irq hook,
which should be early enough.

Reported-by: Kevin Hilman <khilman@kernel.org>
Fixes: 8fb76a07e2 ("ARM: imx6: set initial power mode in pm function")
Tested-by: Kevin Hilman <khilman@linaro.org>
Tested-by: Tyler Baker <tyler.baker@linaro.org>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>

arch/arm/mach-imx/common.h

@@ -123,6 +123,7 @@ static inline void v7_cpu_resume(void) {}
 static inline void imx6_suspend(void __iomem *ocram_vbase) {}
 #endif
 
+void imx6_pm_ccm_init(const char *ccm_compat);
 void imx6q_pm_init(void);
 void imx6dl_pm_init(void);
 void imx6sl_pm_init(void);

arch/arm/mach-imx/mach-imx6q.c

@@ -393,6 +393,7 @@ static void __init imx6q_init_irq(void)
 	imx_init_l2cache();
 	imx_src_init();
 	irqchip_init();
+	imx6_pm_ccm_init("fsl,imx6q-ccm");
 }
 
 static const char * const imx6q_dt_compat[] __initconst = {

arch/arm/mach-imx/mach-imx6sl.c

@@ -66,6 +66,7 @@ static void __init imx6sl_init_irq(void)
 	imx_init_l2cache();
 	imx_src_init();
 	irqchip_init();
+	imx6_pm_ccm_init("fsl,imx6sl-ccm");
 }
 
 static const char * const imx6sl_dt_compat[] __initconst = {

arch/arm/mach-imx/mach-imx6sx.c

@@ -86,6 +86,7 @@ static void __init imx6sx_init_irq(void)
 	imx_init_l2cache();
 	imx_src_init();
 	irqchip_init();
+	imx6_pm_ccm_init("fsl,imx6sx-ccm");
 }
 
 static void __init imx6sx_init_late(void)

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

@@ -89,7 +89,6 @@ struct imx6_pm_base {
 
 struct imx6_pm_socdata {
 	u32 ddr_type;
-	const char *ccm_compat;
 	const char *mmdc_compat;
 	const char *src_compat;
 	const char *iomuxc_compat;
@@ -139,7 +138,6 @@ static const u32 imx6sx_mmdc_io_offset[] __initconst = {
 };
 
 static const struct imx6_pm_socdata imx6q_pm_data __initconst = {
-	.ccm_compat = "fsl,imx6q-ccm",
 	.mmdc_compat = "fsl,imx6q-mmdc",
 	.src_compat = "fsl,imx6q-src",
 	.iomuxc_compat = "fsl,imx6q-iomuxc",
@@ -149,7 +147,6 @@ static const struct imx6_pm_socdata imx6q_pm_data __initconst = {
 };
 
 static const struct imx6_pm_socdata imx6dl_pm_data __initconst = {
-	.ccm_compat = "fsl,imx6q-ccm",
 	.mmdc_compat = "fsl,imx6q-mmdc",
 	.src_compat = "fsl,imx6q-src",
 	.iomuxc_compat = "fsl,imx6dl-iomuxc",
@@ -159,7 +156,6 @@ static const struct imx6_pm_socdata imx6dl_pm_data __initconst = {
 };
 
 static const struct imx6_pm_socdata imx6sl_pm_data __initconst = {
-	.ccm_compat = "fsl,imx6sl-ccm",
 	.mmdc_compat = "fsl,imx6sl-mmdc",
 	.src_compat = "fsl,imx6sl-src",
 	.iomuxc_compat = "fsl,imx6sl-iomuxc",
@@ -169,7 +165,6 @@ static const struct imx6_pm_socdata imx6sl_pm_data __initconst = {
 };
 
 static const struct imx6_pm_socdata imx6sx_pm_data __initconst = {
-	.ccm_compat = "fsl,imx6sx-ccm",
 	.mmdc_compat = "fsl,imx6sx-mmdc",
 	.src_compat = "fsl,imx6sx-src",
 	.iomuxc_compat = "fsl,imx6sx-iomuxc",
@@ -553,16 +548,11 @@ put_node:
 static void __init imx6_pm_common_init(const struct imx6_pm_socdata
 					*socdata)
 {
-	struct device_node *np;
 	struct regmap *gpr;
 	int ret;
 
-	np = of_find_compatible_node(NULL, NULL, socdata->ccm_compat);
-	ccm_base = of_iomap(np, 0);
 	WARN_ON(!ccm_base);
 
-	imx6_set_lpm(WAIT_CLOCKED);
-
 	if (IS_ENABLED(CONFIG_SUSPEND)) {
 		ret = imx6q_suspend_init(socdata);
 		if (ret)
@@ -583,6 +573,24 @@ static void __init imx6_pm_common_init(const struct imx6_pm_socdata
 				   IMX6Q_GPR1_GINT);
 }
 
+void __init imx6_pm_ccm_init(const char *ccm_compat)
+{
+	struct device_node *np;
+	u32 val;
+
+	np = of_find_compatible_node(NULL, NULL, ccm_compat);
+	ccm_base = of_iomap(np, 0);
+	BUG_ON(!ccm_base);
+
+	/*
+	 * Initialize CCM_CLPCR_LPM into RUN mode to avoid ARM core
+	 * clock being shut down unexpectedly by WAIT mode.
+	 */
+	val = readl_relaxed(ccm_base + CLPCR);
+	val &= ~BM_CLPCR_LPM;
+	writel_relaxed(val, ccm_base + CLPCR);
+}
+
 void __init imx6q_pm_init(void)
 {
 	imx6_pm_common_init(&imx6q_pm_data);