Re: [PATCH v2 1/2] clk: samsung: exynos4: Enable ARMCLK down feature

Mike Turquette
2014-07-24T00:18:59Z

Quoting Krzysztof Kozlowski (2014-07-18 07:36:32)
> 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)

Nice power savings! Just a quick question on this feature: the clock
frequency is changed in hardware as a result of WFI/WFE? And this only
happens when all CPUs in a cluster (e.g. all 4 CPUs in Exynos 4412) are
in WFI/WFE state?

Thanks,
Mike

>
> 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>
>
> ---
>
> Changes since v1:
> 1. Add PWR_CTRL registers to the list of saved clk registers on
> Exynos4x12. Suggested by Tomasz Figa.
> 2. Disable the clock up feature. (sug. Tomasz Figa)
> 3. Use macros for setting clock down ratio. (sug. Tomasz Figa)
> 4. Use num_possible_cpus() for exception on Exynos4x12. (sug. Tomasz
> Figa)
> 5. Enable the clock down feature also on Exynos4210 Trats board.
> ---
> drivers/clk/samsung/clk-exynos4.c | 46 +++++++++++++++++++++++++++++++++++++++
> 1 file changed, 46 insertions(+)
>
> diff --git a/drivers/clk/samsung/clk-exynos4.c b/drivers/clk/samsung/clk-exynos4.c
> index 7f4a473a7ad7..86c7709dc6d6 100644
> --- a/drivers/clk/samsung/clk-exynos4.c
> +++ b/drivers/clk/samsung/clk-exynos4.c
> @@ -114,11 +114,27 @@
> #define DIV_CPU1 0x14504
> #define GATE_SCLK_CPU 0x14800
> #define GATE_IP_CPU 0x14900
> +#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,
> @@ -155,6 +171,7 @@ 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 = {
> @@ -164,6 +181,8 @@ 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 = {
> @@ -1164,6 +1183,32 @@ 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)
> @@ -1250,6 +1295,7 @@ 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();
>
> pr_info("%s clocks: sclk_apll = %ld, sclk_mpll = %ld\n"
> --
> 1.9.1
>