linux-kernel - Re: [PATCH net-next v2 1/6] dpll: zl3073x: Store raw register values instead of parsed state

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Message-ID: <45a93065-eaaa-4b18-90e0-e1d9cceb91b4@redhat.com>
Date: Wed, 12 Nov 2025 20:24:13 +0100
From: Ivan Vecera <ivecera@...hat.com>
To: Vadim Fedorenko <vadim.fedorenko@...ux.dev>, netdev@...r.kernel.org
Cc: Petr Oros <poros@...hat.com>,
 Prathosh Satish <Prathosh.Satish@...rochip.com>,
 Arkadiusz Kubalewski <arkadiusz.kubalewski@...el.com>,
 Jiri Pirko <jiri@...nulli.us>, Michal Schmidt <mschmidt@...hat.com>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v2 1/6] dpll: zl3073x: Store raw register values
 instead of parsed state

On 11/12/25 3:12 PM, Vadim Fedorenko wrote:
> On 11/11/2025 18:12, Ivan Vecera wrote:
>> The zl3073x_ref, zl3073x_out and zl3073x_synth structures
>> previously stored state that was parsed from register reads. This
>> included values like boolean 'enabled' flags, synthesizer selections,
>> and pre-calculated frequencies.
>>
>> This commit refactors the state management to store the raw register
>> values directly in these structures. The various inline helper functions
>> are updated to parse these raw values on-demand using FIELD_GET.
>>
>> Reviewed-by: Petr Oros <poros@...hat.com>
>> Tested-by: Prathosh Satish <Prathosh.Satish@...rochip.com>
>> Signed-off-by: Ivan Vecera <ivecera@...hat.com>
>> ---
>>   drivers/dpll/zl3073x/core.c | 81 ++++++++++++-------------------------
>>   drivers/dpll/zl3073x/core.h | 61 ++++++++++++++++------------
>>   2 files changed, 60 insertions(+), 82 deletions(-)
>>
>> diff --git a/drivers/dpll/zl3073x/core.c b/drivers/dpll/zl3073x/core.c
>> index e42e527813cf8..50c1fe59bc7f0 100644
>> --- a/drivers/dpll/zl3073x/core.c
>> +++ b/drivers/dpll/zl3073x/core.c
>> @@ -598,25 +598,22 @@ int zl3073x_write_hwreg_seq(struct zl3073x_dev 
>> *zldev,
>>    * @zldev: pointer to zl3073x_dev structure
>>    * @index: input reference index to fetch state for
>>    *
>> - * Function fetches information for the given input reference that are
>> - * invariant and stores them for later use.
>> + * Function fetches state for the given input reference and stores it 
>> for
>> + * later user.
>>    *
>>    * Return: 0 on success, <0 on error
>>    */
>>   static int
>>   zl3073x_ref_state_fetch(struct zl3073x_dev *zldev, u8 index)
>>   {
>> -    struct zl3073x_ref *input = &zldev->ref[index];
>> -    u8 ref_config;
>> +    struct zl3073x_ref *ref = &zldev->ref[index];
>>       int rc;
>>       /* If the input is differential then the configuration for N-pin
>>        * reference is ignored and P-pin config is used for both.
>>        */
>> -    if (zl3073x_is_n_pin(index) &&
>> -        zl3073x_ref_is_diff(zldev, index - 1)) {
>> -        input->enabled = zl3073x_ref_is_enabled(zldev, index - 1);
>> -        input->diff = true;
>> +    if (zl3073x_is_n_pin(index) && zl3073x_ref_is_diff(zldev, index - 
>> 1)) {
>> +        memcpy(ref, &zldev->ref[index - 1], sizeof(*ref));
> 
> Oh, it's not obvious from the code that it's actually safe, unless
> reviewer remembers that N-pins have only even indexes.

Would it be helpful to add here the comment describing that is safe and
why?

> Have you thought of adding an abstraction for differential pair pins?

No, zl3073x_ref represents mailbox for HW reference... Here, I’m just
following the datasheet, which states: "If the P-pin is marked as
differential then some content of the mailbox for N-pin is ignored and
is inherited from the P-pin".
For now, the content of zl3073x_ref is the inherited one, but this may
change in the future.

The abstraction for differential pin pairs is actually handled in
dpll.c, where only a single dpll_pin is registered for each such pair.

Ivan