[U-Boot] [PATCH v2 1/2] imx: mx6: add get_cpu_speed_grade_hz func to return MHz speed grade from OTP

[Stefano Babic]

Hi Christian,

On 15/05/2015 09:53, Christian Gmeiner wrote:
> Hi
> 
> 2015-05-14 7:08 GMT+02:00 Tim Harvey <tharvey at gateworks.com>:
>> The IMX6 has four different speed grades determined by eFUSE SPEED_GRADING
>> indicated by OCOTP_CFG3[17:16] which is at 0x440 in the Fusemap Description
>> Table. Return this frequency so that it can be used elsewhere.
>>
>> Note that the IMX6SDLRM and the IMX6SXRM do not indicate this in the
>> their Fusemap Description Table however Freescale has confirmed that these
>> eFUSE bits match the description within the IMX6DQRM and that they will
>> be added to the next revision of the respective reference manuals.
>>
>> These have been tested with IMX6 Quad/Solo/Dual-light 800Mhz and 1GHz grades.
>>
>> Signed-off-by: Tim Harvey <tharvey at gateworks.com>
>> ---
>>  arch/arm/cpu/armv7/mx6/soc.c              | 41 +++++++++++++++++++++++++++++++
>>  arch/arm/include/asm/arch-mx6/sys_proto.h |  1 +
>>  2 files changed, 42 insertions(+)
>>
>> diff --git a/arch/arm/cpu/armv7/mx6/soc.c b/arch/arm/cpu/armv7/mx6/soc.c
>> index dd34138..71fa1fb 100644
>> --- a/arch/arm/cpu/armv7/mx6/soc.c
>> +++ b/arch/arm/cpu/armv7/mx6/soc.c
>> @@ -83,6 +83,47 @@ u32 get_cpu_rev(void)
>>         return (type << 12) | (reg + 0x10);
>>  }
>>
>> +/*
>> + * OCOTP_CFG3[17:16] (see Fusemap Description Table offset 0x440)
>> + * defines a 2-bit SPEED_GRADING
>> + */
>> +#define OCOTP_CFG3_SPEED_SHIFT 16
>> +#define OCOTP_CFG3_SPEED_800MHZ        0
>> +#define OCOTP_CFG3_SPEED_850MHZ        1
>> +#define OCOTP_CFG3_SPEED_1GHZ  2
>> +#define OCOTP_CFG3_SPEED_1P2GHZ        3
> 
> Note: 0x3 is defined as reserved (IMX6DQRM Rev 2, 06/2014).
> 

That means that the manual is buggy, if the SOC returns exactly this
value ;-)

>> +
>> +u32 get_cpu_speed_grade_hz(void)
>> +{
>> +       struct ocotp_regs *ocotp = (struct ocotp_regs *)OCOTP_BASE_ADDR;
>> +       struct fuse_bank *bank = &ocotp->bank[0];
>> +       struct fuse_bank0_regs *fuse =
>> +               (struct fuse_bank0_regs *)bank->fuse_regs;
>> +       uint32_t val;
>> +
>> +       val = readl(&fuse->cfg3);
>> +       val >>= OCOTP_CFG3_SPEED_SHIFT;
>> +       val &= 0x3;
>> +
>> +       switch (val) {
>> +       /* Valid for IMX6DQ */
>> +       case OCOTP_CFG3_SPEED_1P2GHZ:
>> +               if (is_cpu_type(MXC_CPU_MX6Q) || is_cpu_type(MXC_CPU_MX6D))
>> +                       return 1200000000;
>> +       /* Valid for IMX6SX/IMX6SDL/IMX6DQ */
>> +       case OCOTP_CFG3_SPEED_1GHZ:
>> +               return 996000000;
>> +       /* Valid for IMX6DQ */
>> +       case OCOTP_CFG3_SPEED_850MHZ:
>> +               if (is_cpu_type(MXC_CPU_MX6Q) || is_cpu_type(MXC_CPU_MX6D))
>> +                       return 852000000;
>> +       /* Valid for IMX6SX/IMX6SDL/IMX6DQ */
>> +       case OCOTP_CFG3_SPEED_800MHZ:
>> +               return 792000000;
>> +       }
>> +       return 0;
> 
> Do we really need the ifs inside the cases? The speed grading fuse
> value is read only and
> we must simply life with the value we read back. So I would drop the
> is_cpu_type(..) thing.

Function does not returns the value of the fuse, else it should returns
val. The value is parsed for consistency, and if it is not, 0 means a
failure. IMHO this interpretation is correct - I would agree with you
only if the return value would be the read value, but it is not.

Best regards,
Stefano Babic

> 
> greets
> --
> Christian Gmeiner, MSc
> 
> https://soundcloud.com/christian-gmeiner
> 


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