ARM: EXYNOS: Get current parent clock for power domain on/off

Using a fixed (by DTS) parent for clocks when turning on the power
domain may introduce issues in other drivers. For example when such
driver changes the parent during runtime and expects that he is the
only place of such change.

Do not rely on DTS providing the fixed parent for such clocks. Instead
before switching domain off, grab a current parent of a clock with
clk_get_parent().
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Reviewed-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Tested-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: Kukjin Kim <kgene@kernel.org>

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

@@ -19,9 +19,10 @@ Optional Properties:
 	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.
+	- clkN: Input clocks to the devices in this power domain. These clocks
+		will be reparented to oscclk before swithing power domain off.
+		Their original parent will be brought back after turning on
+		the domain. Maximum of 4 clocks (N = 0 to 3) are supported.
 	- asbN: Clocks required by asynchronous bridges (ASB) present in
 		the power domain. These clock should be enabled during power
 		domain on/off operations.

arch/arm/mach-exynos/pm_domains.c

@@ -62,6 +62,7 @@ static int exynos_pd_power(struct generic_pm_domain *domain, bool power_on)
 		for (i = 0; i < MAX_CLK_PER_DOMAIN; i++) {
 			if (IS_ERR(pd->clk[i]))
 				break;
+			pd->pclk[i] = clk_get_parent(pd->clk[i]);
 			if (clk_set_parent(pd->clk[i], pd->oscclk))
 				pr_err("%s: error setting oscclk as parent to clock %d\n",
 						pd->name, i);
@@ -90,6 +91,9 @@ static int exynos_pd_power(struct generic_pm_domain *domain, bool power_on)
 		for (i = 0; i < MAX_CLK_PER_DOMAIN; i++) {
 			if (IS_ERR(pd->clk[i]))
 				break;
+
+			if (IS_ERR(pd->clk[i]))
+				continue; /* Skip on first power up */
 			if (clk_set_parent(pd->clk[i], pd->pclk[i]))
 				pr_err("%s: error setting parent to clock%d\n",
 						pd->name, i);
@@ -182,13 +186,11 @@ static __init int exynos4_pm_init_power_domain(void)
 			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;
-			}
+			/*
+			 * Skip setting parent on first power up.
+			 * The parent at this time may not be useful at all.
+			 */
+			pd->pclk[i] = ERR_PTR(-EINVAL);
 		}
 
 		if (IS_ERR(pd->clk[0]))