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

[Baruch Siach]

Hi Chris,

On Tue, Jun 25 2019, Chris Packham wrote:
> 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.

Is there AVS feedback circuit on these boards? If so, have you measured
how this patch affects core voltage?

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

Thanks,
baruch

>> ---
>>  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.

--
     http://baruch.siach.name/blog/                  ~. .~   Tk Open Systems
=}------------------------------------------------ooO--U--Ooo------------{=
   - baruch at tkos.co.il - tel: +972.52.368.4656, http://www.tkos.co.il -