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

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Date: Wed, 7 Feb 2024 12:53:47 +0530
From: CHANDRU DHAVAMANI <chandru@...com>
To: "Kumar, Udit" <u-kumar1@...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 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.


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