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

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Date: Wed, 7 Feb 2024 13:36:05 +0530
From: CHANDRU DHAVAMANI <chandru@...com>
To: "Kumar, Udit" <u-kumar1@...com>, Kamlesh Gurudasani <kamlesh@...com>,
        Nishanth Menon <nm@...com>, <vishalm@...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 07/02/24 13:03, Kumar, Udit wrote:
>
> 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
>

Okay. We can use TI_SCI_MSG_GET_CLOCK_STATE to check to if clock is 
valid or not.


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