Re: [PATCH v3 net-next 5/8] mfd: zl3073x: Add functions to work with register mailboxes

Ivan Vecera
2025-04-17T14:15:53Z

On 17. 04. 25 3:27 odp., Andrew Lunn wrote:
>> Anyway, I have a different idea... completely abstract mailboxes from the
>> caller. The mailbox content can be large and the caller is barely interested
>> in all registers from the mailbox but this could be resolved this way:
>>
>> The proposed API e.g for Ref mailbox:
>>
>> int zl3073x_mb_ref_read(struct zl3073x_dev *zldev, u8 index,
>> struct zl3073x_mb_ref *mb);
>> int zl3073x_mb_ref_write(struct zl3073x_dev *zldev, u8 index,
>> struct zl3073x_mb_ref *mb);
>>
>> struct zl3073x_mb_ref {
>> u32 flags;
>> u16 freq_base;
>> u16 freq_mult;
>> u16 ratio_m;
>> u16 ratio_n;
>> u8 config;
>> u64 phase_offset_compensation;
>> u8 sync_ctrl;
>> u32 esync_div;
>> }
>>
>> #define ZL3073X_MB_REF_FREQ_BASE BIT(0)
>> #define ZL3073X_MB_REF_FREQ_MULT BIT(1)
>> #define ZL3073X_MB_REF_RATIO_M BIT(2)
>> #define ZL3073X_MB_REF_RATIO_N BIT(3)
>> #define ZL3073X_MB_REF_CONFIG BIT(4)
>> #define ZL3073X_MB_REF_PHASE_OFFSET_COMPENSATION BIT(5)
>> #define ZL3073X_MB_REF_SYNC_CTRL BIT(6)
>> #define ZL3073X_MB_REF_ESYNC_DIV BIT(7)
>>
>> Then a reader can read this way (read freq and ratio of 3rd ref):
>> {
>> struct zl3073x_mb_ref mb;
>> ...
>> mb.flags = ZL3073X_MB_REF_FREQ_BASE |
>> ZL3073X_MB_REF_FREQ_MULT |
>> ZL3073X_MB_REF_RATIO_M |
>> ZL3073X_MB_REF_RATIO_N;
>> rc = zl3073x_mb_ref_read(zldev, 3, &mb);
>> if (rc)
>> return rc;
>> /* at this point mb fields requested via flags are filled */
>> }
>> A writer similarly (write config of 5th ref):
>> {
>> struct zl3073x_mb_ref mb;
>> ...
>> mb.flags = ZL3073X_MB_REF_CONFIG;
>> mb.config = FIELD_PREP(SOME_MASK, SOME_VALUE);
>> rc = zl3073x_mb_ref_write(zldev, 5, &mb);
>> ...
>> /* config of 5th ref was commited */
>> }
>>
>> The advantages:
>> * no explicit locking required from the callers
>> * locking is done inside mailbox API
>> * each mailbox type can have different mutex so multiple calls for
>> different mailbox types (e.g ref & output) can be done in parallel
>>
>> WDYT about this approach?
>
> I would say this is actually your next layer on top of the basic
> mailbox API. This makes it more friendly to your sub driver and puts
> all the locking in one place where it can easily be reviewed.
>
> One question would be, where does this code belong. Is it in the MFD,
> or in the subdrivers? I guess it is in the subdrivers.

No, it should be part of MFD because it does not make sense to implement
API above in each sub-driver separately.

Sub-driver would use this MB ABI for MB access and
zl3073x_{read,write}_u{8,16,32,48} for non-MB registers.

Ivan