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

[Krzysztof Kozlowski]

On czw, 2014-07-24 at 08:42 +0200, Krzysztof Kozlowski wrote:
> On Åro, 2014-07-23 at 17:18 -0700, Mike Turquette wrote:
> > 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?
> 
> Yes. This feature makes changes in DIVCORE and DIVCORE2 clock dividers
> when given core enters 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?
> 
> No, this is per-core. However measured energy savings above were in case
> where all cores entered idle (WFI).

Aaargh, that is obviously incorrect, my mistake. You're right that this
is for whole cluster as all cores share ARMCLK (and clock dividers).
However you can enable WFI/WFE detection per core. 

The datasheet does not describe what will happen exactly when you enable
the WFI/WFE detection for core0 and leave it disabled for other cores. I
assume that upon entering WFI on core0 everything will be slowed down
regardless of pending work on other cores but I didn't test it.

Best regards,
Krzysztof

> 
> Best regards,
> Krzysztof
> 
> 
> > 
> > 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@xxxxxxxxxxx>
> > > 
> > > ---
> > > 
> > > 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
> > > 

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