ARM: EXYNOS: Add support for clock handling in power domain

While powering on/off a local powerdomain in exynos5 chipsets, the
input clocks to each device gets modified. This behaviour is based
on the SYSCLK_SYS_PWR_REG registers.
E.g. SYSCLK_MFC_SYS_PWR_REG = 0x0, the parent of input clock to MFC
                             (aclk333) gets modified to oscclk
                            = 0x1, no change in clocks.
The recommended value of SYSCLK_SYS_PWR_REG before power gating any
domain is 0x0. So we must also restore the clocks while powering on
a domain everytime.

This patch adds the framework for getting the required mux and parent
clocks through a power domain device node. With this patch, while
powering off a domain, parent is set to oscclk and while powering back
on, its re-set to the correct parent which is as per the recommended
pd on/off sequence.
Signed-off-by: Prathyush K <prathyush.k@samsung.com>
Signed-off-by: Andrew Bresticker <abrestic@chromium.org>
Signed-off-by: Arun Kumar K <arun.kk@samsung.com>
Signed-off-by: Shaik Ameer Basha <shaik.ameer@samsung.com>
Reviewed-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>

Documentation/devicetree/bindings/arm/exynos/power_domain.txt

@@ -9,6 +9,18 @@ Required Properties:
 - reg: physical base address of the controller and length of memory mapped
     region.
 
+Optional Properties:
+- clocks: List of clock handles. The parent clocks of the input clocks to the
+	devices in this power domain are set to oscclk before power gating
+	and restored back after powering on a domain. This is required for
+	all domains which are powered on and off and not required for unused
+	domains.
+- clock-names: The following clocks can be specified:
+	- oscclk: Oscillator clock.
+	- pclkN, clkN: Pairs of parent of input clock and input clock to the
+		devices in this power domain. Maximum of 4 pairs (N = 0 to 3)
+		are supported currently.
+
 Node of a device using power domains must have a samsung,power-domain property
 defined with a phandle to respective power domain.
 
@@ -19,6 +31,14 @@ Example:
 		reg = <0x10023C00 0x10>;
 	};
 
+	mfc_pd: power-domain@10044060 {
+		compatible = "samsung,exynos4210-pd";
+		reg = <0x10044060 0x20>;
+		clocks = <&clock CLK_FIN_PLL>, <&clock CLK_MOUT_SW_ACLK333>,
+			<&clock CLK_MOUT_USER_ACLK333>;
+		clock-names = "oscclk", "pclk0", "clk0";
+	};
+
 Example of the node using power domain:
 
 	node {

arch/arm/mach-exynos/pm_domains.c

@@ -17,6 +17,7 @@
 #include <linux/err.h>
 #include <linux/slab.h>
 #include <linux/pm_domain.h>
+#include <linux/clk.h>
 #include <linux/delay.h>
 #include <linux/of_address.h>
 #include <linux/of_platform.h>
@@ -24,6 +25,8 @@
 
 #include "regs-pmu.h"
 
+#define MAX_CLK_PER_DOMAIN	4
+
 /*
  * Exynos specific wrapper around the generic power domain
  */
@@ -32,6 +35,9 @@ struct exynos_pm_domain {
 	char const *name;
 	bool is_off;
 	struct generic_pm_domain pd;
+	struct clk *oscclk;
+	struct clk *clk[MAX_CLK_PER_DOMAIN];
+	struct clk *pclk[MAX_CLK_PER_DOMAIN];
 };
 
 static int exynos_pd_power(struct generic_pm_domain *domain, bool power_on)
@@ -44,6 +50,19 @@ static int exynos_pd_power(struct generic_pm_domain *domain, bool power_on)
 	pd = container_of(domain, struct exynos_pm_domain, pd);
 	base = pd->base;
 
+	/* Set oscclk before powering off a domain*/
+	if (!power_on) {
+		int i;
+
+		for (i = 0; i < MAX_CLK_PER_DOMAIN; i++) {
+			if (IS_ERR(pd->clk[i]))
+				break;
+			if (clk_set_parent(pd->clk[i], pd->oscclk))
+				pr_err("%s: error setting oscclk as parent to clock %d\n",
+						pd->name, i);
+		}
+	}
+
 	pwr = power_on ? S5P_INT_LOCAL_PWR_EN : 0;
 	__raw_writel(pwr, base);
 
@@ -60,6 +79,20 @@ static int exynos_pd_power(struct generic_pm_domain *domain, bool power_on)
 		cpu_relax();
 		usleep_range(80, 100);
 	}
+
+	/* Restore clocks after powering on a domain*/
+	if (power_on) {
+		int i;
+
+		for (i = 0; i < MAX_CLK_PER_DOMAIN; i++) {
+			if (IS_ERR(pd->clk[i]))
+				break;
+			if (clk_set_parent(pd->clk[i], pd->pclk[i]))
+				pr_err("%s: error setting parent to clock%d\n",
+						pd->name, i);
+		}
+	}
+
 	return 0;
 }
 
@@ -152,9 +185,11 @@ static __init int exynos4_pm_init_power_domain(void)
 
 	for_each_compatible_node(np, NULL, "samsung,exynos4210-pd") {
 		struct exynos_pm_domain *pd;
-		int on;
+		int on, i;
+		struct device *dev;
 
 		pdev = of_find_device_by_node(np);
+		dev = &pdev->dev;
 
 		pd = kzalloc(sizeof(*pd), GFP_KERNEL);
 		if (!pd) {
@@ -170,6 +205,30 @@ static __init int exynos4_pm_init_power_domain(void)
 		pd->pd.power_on = exynos_pd_power_on;
 		pd->pd.of_node = np;
 
+		pd->oscclk = clk_get(dev, "oscclk");
+		if (IS_ERR(pd->oscclk))
+			goto no_clk;
+
+		for (i = 0; i < MAX_CLK_PER_DOMAIN; i++) {
+			char clk_name[8];
+
+			snprintf(clk_name, sizeof(clk_name), "clk%d", i);
+			pd->clk[i] = clk_get(dev, clk_name);
+			if (IS_ERR(pd->clk[i]))
+				break;
+			snprintf(clk_name, sizeof(clk_name), "pclk%d", i);
+			pd->pclk[i] = clk_get(dev, clk_name);
+			if (IS_ERR(pd->pclk[i])) {
+				clk_put(pd->clk[i]);
+				pd->clk[i] = ERR_PTR(-EINVAL);
+				break;
+			}
+		}
+
+		if (IS_ERR(pd->clk[0]))
+			clk_put(pd->oscclk);
+
+no_clk:
 		platform_set_drvdata(pdev, pd);
 
 		on = __raw_readl(pd->base + 0x4) & S5P_INT_LOCAL_PWR_EN;