linux-kernel - Re: [PATCH v2] clk: keystone: sci-clk: Adding support for non contiguous clocks

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Date: Wed, 7 Feb 2024 13:03:37 +0530
From: "Kumar, Udit" <u-kumar1@...com>
To: CHANDRU DHAVAMANI <chandru@...com>, Kamlesh Gurudasani <kamlesh@...com>,
        Nishanth Menon <nm@...com>
CC: <kristo@...nel.org>, <ssantosh@...nel.org>, <rishabh@...com>,
        <vigneshr@...com>, <mturquette@...libre.com>, <sboyd@...nel.org>,
        <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>,
        <linux-clk@...r.kernel.org>
Subject: Re: [PATCH v2] clk: keystone: sci-clk: Adding support for non
 contiguous clocks


On 2/7/2024 12:53 PM, CHANDRU DHAVAMANI wrote:
>
> On 07/02/24 11:03, Kumar, Udit wrote:
>>
>> On 2/6/2024 9:24 PM, Kamlesh Gurudasani wrote:
>>> "Kumar, Udit" <u-kumar1@...com> writes:
>>>
>>>>>>>> get_freq is a bit expensive as it has to walk the clock tree to 
>>>>>>>> find
>>>>>>>> the clock frequency (at least the first time?). just wondering if
>>>>>>>> there is lighter alternative here?
>>>>>>>>
>>>>>>> How about get_clock? Doesn't read the registers at least.
>>>>>> Said API needs, some flags to be passed,
>>>>>>
>>>>>> Can those flag be set to zero, Chandru ?
>>>>>
>>>>> get_clock doesn't require any flags to be passed.
>>>>
>>>> May be firmware does not need it but  I was referring to
>>>>
>>>> https://elixir.bootlin.com/linux/latest/source/drivers/clk/keystone/sci-clk.c#L78 
>>>>
>>> Just took a look,
>>>
>>> I now understand the reason for confusion,
>>>
>>> #define TI_SCI_MSG_SET_CLOCK_STATE    0x0100
>>> #define TI_SCI_MSG_GET_CLOCK_STATE    0x0101
>>>
>>> cops->get_clock = ti_sci_cmd_get_clock;  --> refers to
>>> TI_SCI_MSG_SET_CLOCK_STATE
>>> That's why we are passing the flag from linux for get_clock
>>>
>>> Linux is using terminology of get/put.
>>>
>>> As Chandru pointed, we don't have to pass flags, cause he is refering
>>> to TI_SCI_MSG_GET_CLOCK_STATE
>>>
>>> Below functions passes TI_SCI_MSG_GET_CLOCK_STATE to DM, which is what
>>> we actually want.
>>> cops->is_auto = ti_sci_cmd_clk_is_auto;
>>> cops->is_on = ti_sci_cmd_clk_is_on;
>>> cops->is_off = ti_sci_cmd_clk_is_off;
>>
>>
>> I think calling ti_sci_cmd_clk_is_auto should be good . other 
>> functions needs current state and requested state.
>>
>> Chandru ?
>>
>
> ti_sci_cmd_clk_is_auto is internal function to linux.
> For TI_SCI_MSG_GET_CLOCK_STATE, linux only needs to pass pointers to 
> the variables where result will be stored.


Yes this internal function calls TI_SCI_MSG_GET_CLOCK_STATE


>
>
>>>
>>> Which should be safe to call, Chandru can confirm.
>>>
>>> Regards,
>>> Kamlesh
>>>>
>>>>
>>>>>
>>>>>>
>>>>>>> Regards,
>>>>>>> Kamlesh