Re: [RFC 03/10] eeprom: starfive: Simplify get_ddr_size_from_eeprom()

E Shattow
2025-09-02T21:28:15Z

On 8/29/25 00:33, Heinrich Schuchardt wrote:
> On 29.08.25 08:09, Hal Feng wrote:
>> Directly return the DDR size instead of the field of 'DxxxExxx'.
>> Move the function description to the header file.
>>
>> Fixes: aea1bd95b61e ("eeprom: starfive: Enable ID EEPROM configuration")
>> Signed-off-by: Hal Feng <hal.feng@starfivetech.com>
>> ---
>>   arch/riscv/cpu/jh7110/spl.c                     |  2 +-
>>   arch/riscv/include/asm/arch-jh7110/eeprom.h     |  8 +++++++-
>>   .../visionfive2/visionfive2-i2c-eeprom.c        | 17 +++--------------
>>   3 files changed, 11 insertions(+), 16 deletions(-)
>>
>> diff --git a/arch/riscv/cpu/jh7110/spl.c b/arch/riscv/cpu/jh7110/spl.c
>> index 87aaf865246..3aece7d995b 100644
>> --- a/arch/riscv/cpu/jh7110/spl.c
>> +++ b/arch/riscv/cpu/jh7110/spl.c
>> @@ -41,7 +41,7 @@ int spl_dram_init(void)
>>       /* Read the definition of the DDR size from eeprom, and if not,
>>        * use the definition in DT
>>        */
>> -    size = (get_ddr_size_from_eeprom() >> 16) & 0xFF;
>> +    size = get_ddr_size_from_eeprom();
>>       if (check_ddr_size(size))
>>           gd->ram_size = size << 30;
>>   diff --git a/arch/riscv/include/asm/arch-jh7110/eeprom.h b/arch/
>> riscv/include/asm/arch-jh7110/eeprom.h
>> index 45ad2a5f7bc..6d0a0ba0c4a 100644
>> --- a/arch/riscv/include/asm/arch-jh7110/eeprom.h
>> +++ b/arch/riscv/include/asm/arch-jh7110/eeprom.h
>> @@ -10,7 +10,13 @@
>>   #include <linux/types.h>
>>     u8 get_pcb_revision_from_eeprom(void);
>> -u32 get_ddr_size_from_eeprom(void);
>> +
>> +/**
>> + * get_ddr_size_from_eeprom() - read DDR size from EEPROM
>> + *
>> + * @return: size in GiB or 0xFF on error.

No. This is not consistent with get_mmc_size_from_eeprom() return value
which uses 0 as short-circuit return value if read_eeprom() fails.

It is not important to make the distinction here if eeprom read failed
or the data was not a valid size (i.e. zero from successful eeprom read).

>> + */
>> +u8 get_ddr_size_from_eeprom(void);
>>     /**
>>    * get_mmc_size_from_eeprom() - read eMMC size from EEPROM
>> diff --git a/board/starfive/visionfive2/visionfive2-i2c-eeprom.c b/
>> board/starfive/visionfive2/visionfive2-i2c-eeprom.c
>> index 17a44020bcf..3866d07f9d4 100644
>> --- a/board/starfive/visionfive2/visionfive2-i2c-eeprom.c
>> +++ b/board/starfive/visionfive2/visionfive2-i2c-eeprom.c
>> @@ -550,23 +550,12 @@ u8 get_pcb_revision_from_eeprom(void)
>>       return pbuf.eeprom.atom1.data.pstr[6];
>>   }
>>   -/**
>> - * get_ddr_size_from_eeprom - get the DDR size
>> - * pstr:  VF7110A1-2228-D008E000-00000001
>> - * VF7110A1/VF7110B1 : VisionFive JH7110A /VisionFive JH7110B
>> - * D008: 8GB LPDDR4
>> - * E000: No emmc device, ECxx: include emmc device, xx: Capacity
>> size[GB]
>> - * return: the field of 'D008E000'
>> - */
>> -
>> -u32 get_ddr_size_from_eeprom(void)
>> +u8 get_ddr_size_from_eeprom(void)
>>   {
>> -    u32 pv = 0xFFFFFFFF;
>> -
>>       if (read_eeprom())
>> -        return pv;
>> +        return 0xFF;

No, inverted logic, see above return of 0xFF as an error condition is
suspect.

>
> Let's assume somebody cleared the EEPROM and the SPI flash.
>
> Would it make sense to assume the minimum encodable RAM size (1 GiB) in
> this case, just to let the board boot to the console to allow writing
> the EEPROM with valid data again?
>
> The current patch to simplify the code looks correct.
>
> Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
>
>>   -    return hextoul(&pbuf.eeprom.atom1.data.pstr[14], NULL);
>> +    return (hextoul(&pbuf.eeprom.atom1.data.pstr[14], NULL) >> 16) &
>> 0xFF;
>>   }
>>     u32 get_mmc_size_from_eeprom(void)
>

Yes, later fallback to 2G size configuration makes sense. Compatible
products with less than 2G do not exist and probably never will; there
may be some developer boards with 1G but none I have ever heard of
directly in conversations since 2023. The other common situation with
zero or uninitialized EEPROM would be a failed read of eeprom i.e. RTC
module at same i2c address or missing devicetree nodes at SPL phase.

1. DDR size detection heuristic should happen first without need of
eeprom, if possible.

2. Else warn DDR detection failed and read size from eeprom config

3. Else warn eeprom memory config invalid and set size set to default 2G.

-E