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

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Date: Wed, 7 Feb 2024 11:03:52 +0530
From: "Kumar, Udit" <u-kumar1@...com>
To: Kamlesh Gurudasani <kamlesh@...com>, CHANDRU DHAVAMANI <chandru@...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 2/6/2024 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 ?

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