[U-Boot] [PATCH] arm: mvebu: set 38x and 39x AVS on lower frequency

[Chris Packham]

Hi Baruch,

On Mon, Jun 24, 2019 at 8:30 PM Baruch Siach <baruch at tkos.co.il> wrote:
>
> Reduce Auto Voltage Scaling VDD limit when core frequency is lower than
> 1600MHz. This reduces core voltage level from 1.25V to 1.15V, which
> saves power.
>
> The code is taken from Marvell's U-Boot 2013.01 revision 18.06.
>
> Signed-off-by: Baruch Siach <baruch at tkos.co.il>

I gave it a quick spin on DB-88F6820-AMC and x530. Both booted fine.

Reviewed-by: Chris Packham <judge.packham at gmail.com>
Tested-by: Chris Packham <judge.packham at gmail.com>

> ---
>  arch/arm/mach-mvebu/include/mach/cpu.h        |  3 +++
>  arch/arm/mach-mvebu/serdes/a38x/sys_env_lib.c | 26 +++++++++++++++++++
>  arch/arm/mach-mvebu/serdes/a38x/sys_env_lib.h |  4 +++
>  arch/arm/mach-mvebu/spl.c                     |  3 +++
>  4 files changed, 36 insertions(+)
>
> diff --git a/arch/arm/mach-mvebu/include/mach/cpu.h b/arch/arm/mach-mvebu/include/mach/cpu.h
> index e6140d67293e..e1128ee90f01 100644
> --- a/arch/arm/mach-mvebu/include/mach/cpu.h
> +++ b/arch/arm/mach-mvebu/include/mach/cpu.h
> @@ -163,6 +163,9 @@ int serdes_phy_config(void);
>   */
>  int ddr3_init(void);
>
> +/* Auto Voltage Scaling */
> +void mv_avs_init(void);
> +
>  /*
>   * get_ref_clk
>   *
> diff --git a/arch/arm/mach-mvebu/serdes/a38x/sys_env_lib.c b/arch/arm/mach-mvebu/serdes/a38x/sys_env_lib.c
> index d387893af37d..e9dd096ad0f5 100644
> --- a/arch/arm/mach-mvebu/serdes/a38x/sys_env_lib.c
> +++ b/arch/arm/mach-mvebu/serdes/a38x/sys_env_lib.c
> @@ -256,3 +256,29 @@ u8 sys_env_device_rev_get(void)
>         value = reg_read(DEV_VERSION_ID_REG);
>         return (value & (REVISON_ID_MASK)) >> REVISON_ID_OFFS;
>  }
> +
> +void mv_avs_init(void)
> +{
> +       u32 sar_freq;
> +
> +       if (!(IS_ENABLED(CONFIG_ARMADA_38X) || IS_ENABLED(CONFIG_ARMADA_39X)))
> +               return;
> +
> +       reg_write(AVS_DEBUG_CNTR_REG, AVS_DEBUG_CNTR_DEFAULT_VALUE);
> +       reg_write(AVS_DEBUG_CNTR_REG, AVS_DEBUG_CNTR_DEFAULT_VALUE);
> +
> +       sar_freq = reg_read(DEVICE_SAMPLE_AT_RESET1_REG);
> +       sar_freq = sar_freq >> SAR_FREQ_OFFSET & SAR_FREQ_MASK;
> +
> +       /* Set AVS value only for core frequency of 1600MHz or less.
> +        * For higher frequency leave the default value.
> +        */
> +       if (sar_freq <= 0xd) {
> +               u32 avs_reg_data = reg_read(AVS_ENABLED_CONTROL);
> +
> +               avs_reg_data &= ~(AVS_LOW_VDD_LIMIT_MASK
> +                               | AVS_HIGH_VDD_LIMIT_MASK);
> +               avs_reg_data |= AVS_LOW_VDD_SLOW_VAL | AVS_HIGH_VDD_SLOW_VAL;
> +               reg_write(AVS_ENABLED_CONTROL, avs_reg_data);
> +       }
> +}
> diff --git a/arch/arm/mach-mvebu/serdes/a38x/sys_env_lib.h b/arch/arm/mach-mvebu/serdes/a38x/sys_env_lib.h
> index 365332d2b048..1774a5b780ca 100644
> --- a/arch/arm/mach-mvebu/serdes/a38x/sys_env_lib.h
> +++ b/arch/arm/mach-mvebu/serdes/a38x/sys_env_lib.h
> @@ -33,6 +33,8 @@
>  #define DEV_ID_REG_DEVICE_ID_OFFS      16
>  #define DEV_ID_REG_DEVICE_ID_MASK      0xffff0000
>
> +#define SAR_FREQ_OFFSET                        10
> +#define SAR_FREQ_MASK                  0x1f
>  #define SAR_DEV_ID_OFFS                        27
>  #define SAR_DEV_ID_MASK                        0x7
>
> @@ -155,10 +157,12 @@
>  #define AVS_LOW_VDD_LIMIT_OFFS         4
>  #define AVS_LOW_VDD_LIMIT_MASK         (0xff << AVS_LOW_VDD_LIMIT_OFFS)
>  #define AVS_LOW_VDD_LIMIT_VAL          (0x27 << AVS_LOW_VDD_LIMIT_OFFS)
> +#define AVS_LOW_VDD_SLOW_VAL           (0x23 << AVS_LOW_VDD_LIMIT_OFFS)
>
>  #define AVS_HIGH_VDD_LIMIT_OFFS                12
>  #define AVS_HIGH_VDD_LIMIT_MASK                (0xff << AVS_HIGH_VDD_LIMIT_OFFS)
>  #define AVS_HIGH_VDD_LIMIT_VAL         (0x27 << AVS_HIGH_VDD_LIMIT_OFFS)
> +#define AVS_HIGH_VDD_SLOW_VAL          (0x23 << AVS_HIGH_VDD_LIMIT_OFFS)
>
>  /* Board ID numbers */
>  #define MARVELL_BOARD_ID_MASK          0x10
> diff --git a/arch/arm/mach-mvebu/spl.c b/arch/arm/mach-mvebu/spl.c
> index d54de5195624..3cb27b7f4b20 100644
> --- a/arch/arm/mach-mvebu/spl.c
> +++ b/arch/arm/mach-mvebu/spl.c
> @@ -126,6 +126,9 @@ void board_init_f(ulong dummy)
>         ddr3_init();
>  #endif
>
> +       /* Initialize Auto Voltage Scaling */
> +       mv_avs_init();
> +
>         /*
>          * Return to the BootROM to continue the Marvell xmodem
>          * UART boot protocol. As initiated by the kwboot tool.
> --
> 2.20.1
>
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