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

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Date: Tue, 6 Feb 2024 21:24:01 +0530
From: Kamlesh Gurudasani <kamlesh@...com>
To: "Kumar, Udit" <u-kumar1@...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>, <u-kumar1@...com>
Subject: Re: [PATCH v2] clk: keystone: sci-clk: Adding support for non
 contiguous clocks

"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;

Which should be safe to call, Chandru can confirm.

Regards,
Kamlesh
>
>
>
>>
>>
>>>
>>>
>>>> Regards,
>>>> Kamlesh