clk: samsung: exynos4: Enable ARMCLK down feature

Enable ARMCLK down feature on all Exynos4 SoCs. The frequency of
ARMCLK will be reduced upon entering idle mode (WFI or WFE).

The feature behaves like very fast cpufreq ondemand governor. In idle
mode this reduces energy consumption on full frequency chosen by
cpufreq governor by approximately:
 - Trats2:  6.5% (153 mA -> 143 mA)
 - Trats:  33.0% (180 mA -> 120 mA)
 - Gear1:  27.0% (180 mA -> 130 mA)

The patch uses simillar settings as Exynos5250 (clk-exynos5250.c),
except it disables clock up feature and on Exynos4412 ARMCLK down is
enabled for all 4 cores.

Tested on Trats board (Exynos4210), Trats2 board (Exynos4412) and
Samsung Gear 1 (Exynos4212).

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Tested-by: Daniel Drake <drake@endlessm.com>
Signed-off-by: Tomasz Figa <t.figa@samsung.com>

drivers/clk/samsung/clk-exynos4.c

@@ -119,11 +119,27 @@
 #define GATE_SCLK_CPU		0x14800
 #define GATE_IP_CPU		0x14900
 #define CLKOUT_CMU_CPU		0x14a00
+#define PWR_CTRL1		0x15020
+#define E4X12_PWR_CTRL2		0x15024
 #define E4X12_DIV_ISP0		0x18300
 #define E4X12_DIV_ISP1		0x18304
 #define E4X12_GATE_ISP0		0x18800
 #define E4X12_GATE_ISP1		0x18804
 
+/* Below definitions are used for PWR_CTRL settings */
+#define PWR_CTRL1_CORE2_DOWN_RATIO(x)		(((x) & 0x7) << 28)
+#define PWR_CTRL1_CORE1_DOWN_RATIO(x)		(((x) & 0x7) << 16)
+#define PWR_CTRL1_DIV2_DOWN_EN			(1 << 9)
+#define PWR_CTRL1_DIV1_DOWN_EN			(1 << 8)
+#define PWR_CTRL1_USE_CORE3_WFE			(1 << 7)
+#define PWR_CTRL1_USE_CORE2_WFE			(1 << 6)
+#define PWR_CTRL1_USE_CORE1_WFE			(1 << 5)
+#define PWR_CTRL1_USE_CORE0_WFE			(1 << 4)
+#define PWR_CTRL1_USE_CORE3_WFI			(1 << 3)
+#define PWR_CTRL1_USE_CORE2_WFI			(1 << 2)
+#define PWR_CTRL1_USE_CORE1_WFI			(1 << 1)
+#define PWR_CTRL1_USE_CORE0_WFI			(1 << 0)
+
 /* the exynos4 soc type */
 enum exynos4_soc {
 	EXYNOS4210,
@@ -160,6 +176,7 @@ static unsigned long exynos4210_clk_save[] __initdata = {
 	E4210_GATE_IP_LCD1,
 	E4210_GATE_IP_PERIR,
 	E4210_MPLL_CON0,
+	PWR_CTRL1,
 };
 
 static unsigned long exynos4x12_clk_save[] __initdata = {
@@ -169,6 +186,8 @@ static unsigned long exynos4x12_clk_save[] __initdata = {
 	E4X12_DIV_ISP,
 	E4X12_DIV_CAM1,
 	E4X12_MPLL_CON0,
+	PWR_CTRL1,
+	E4X12_PWR_CTRL2,
 };
 
 static unsigned long exynos4_clk_pll_regs[] __initdata = {
@@ -1337,6 +1356,32 @@ static struct samsung_pll_clock exynos4x12_plls[nr_plls] __initdata = {
 			VPLL_LOCK, VPLL_CON0, NULL),
 };
 
+static void __init exynos4_core_down_clock(enum exynos4_soc soc)
+{
+	unsigned int tmp;
+
+	/*
+	 * Enable arm clock down (in idle) and set arm divider
+	 * ratios in WFI/WFE state.
+	 */
+	tmp = (PWR_CTRL1_CORE2_DOWN_RATIO(7) | PWR_CTRL1_CORE1_DOWN_RATIO(7) |
+		PWR_CTRL1_DIV2_DOWN_EN | PWR_CTRL1_DIV1_DOWN_EN |
+		PWR_CTRL1_USE_CORE1_WFE | PWR_CTRL1_USE_CORE0_WFE |
+		PWR_CTRL1_USE_CORE1_WFI | PWR_CTRL1_USE_CORE0_WFI);
+	/* On Exynos4412 enable it also on core 2 and 3 */
+	if (num_possible_cpus() == 4)
+		tmp |= PWR_CTRL1_USE_CORE3_WFE | PWR_CTRL1_USE_CORE2_WFE |
+		       PWR_CTRL1_USE_CORE3_WFI | PWR_CTRL1_USE_CORE2_WFI;
+	__raw_writel(tmp, reg_base + PWR_CTRL1);
+
+	/*
+	 * Disable the clock up feature on Exynos4x12, in case it was
+	 * enabled by bootloader.
+	 */
+	if (exynos4_soc == EXYNOS4X12)
+		__raw_writel(0x0, reg_base + E4X12_PWR_CTRL2);
+}
+
 /* register exynos4 clocks */
 static void __init exynos4_clk_init(struct device_node *np,
 				    enum exynos4_soc soc)
@@ -1431,6 +1476,7 @@ static void __init exynos4_clk_init(struct device_node *np,
 	samsung_clk_register_alias(ctx, exynos4_aliases,
 			ARRAY_SIZE(exynos4_aliases));
 
+	exynos4_core_down_clock(soc);
 	exynos4_clk_sleep_init();
 
 	samsung_clk_of_add_provider(np, ctx);