From: Maxime Coquelin <maxime.coquelin@st.com>
To: Lee Jones <lee.jones@linaro.org>, Jassi Brar <jassisinghbrar@gmail.com>
Cc: Devicetree List <devicetree@vger.kernel.org>,
Mike Turquette <mturquette@linaro.org>, <kernel@stlinux.com>,
Stephen Boyd <sboyd@codeaurora.org>,
lkml <linux-kernel@vger.kernel.org>,
Jassi Brar <jaswinder.singh@linaro.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [STLinux Kernel] [PATCH 3/4] clk: Provide always-on clock support
Date: Mon, 2 Mar 2015 11:25:28 +0100 [thread overview]
Message-ID: <54F43A98.509@st.com> (raw)
In-Reply-To: <20150302101859.GB32347@x1>
On 03/02/2015 11:18 AM, Lee Jones wrote:
> On Mon, 02 Mar 2015, Jassi Brar wrote:
>
>> On Mon, Mar 2, 2015 at 2:06 PM, Lee Jones <lee.jones@linaro.org> wrote:
>>> On Sat, 28 Feb 2015, Jassi Brar wrote:
>>>
>>>> On 28 February 2015 at 02:44, Lee Jones <lee.jones@linaro.org> wrote:
>>>>> Lots of platforms contain clocks which if turned off would prove fatal.
>>>>> The only way to recover from these catastrophic failures is to restart
>>>>> the board(s). Now, when a clock is registered with the framework it is
>>>>> compared against a list of provided always-on clock names which must be
>>>>> kept ungated. If it matches, we enable the existing CLK_IGNORE_UNUSED
>>>>> flag, which will prevent the common clk framework from attempting to
>>>>> gate it during the clk_disable_unused() procedure.
>>>>>
>>>> If a clock is critical on a certain board, it could be got+enabled
>>>> during early boot so there is always a user.
>>> I tried this. There was push-back from the DT maintainers.
>>>
>>> http://lists.infradead.org/pipermail/linux-arm-kernel/2015-February/324417.html
>>>
>> Thanks, I wasn't aware of the history.
>>
>>>> To be able to do that from DT, maybe add a new, say, CLK_ALWAYS_ON
>>>> flag could be made to initialize the clock with one phantom user
>>>> already. Or just reuse the CLK_IGNORE_UNUSED?
>>> How is that different to what this set is doing?
>>>
>> The phantom user - that's there but none can see it.
>>
>> How about?
>>
>> + of_property_for_each_string(np, "clock-always-on", prop, clkname) {
>> + clk = __clk_lookup(clkname);
>> + if (!clk)
>> + continue;
>> +
>> + clk->core->enable_count = 1;
>> + clk->core->prepare_count = 1;
>> + }
> This is only fractionally different from the current implementation.
>
> I believe the current way it slightly nicer, as we don't have to fake
> the user count. This solution is saying "one of the drivers is still
> consuming this clock", instead, in the original implementation we're
> saying "we know there are no consumers of this clock, but keep it on
> anyway due to [insert reason here]".
>
So maybe introducing a new "CLK_DISABLE_NEVER" flag will be more
explicit than hacking around "CLK_IGNORE_UNUSED" one?
BR,
Maxime
next prev parent reply other threads:[~2015-03-02 10:26 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-27 21:14 [PATCH 0/4] clk: Provide support for always-on clocks Lee Jones
2015-02-27 21:14 ` [PATCH 1/4] ARM: sti: stih407-family: Supply defines for CLOCKGEN A0 Lee Jones
2015-02-27 21:14 ` [PATCH 2/4] ARM: sti: stih410-clocks: Identify critical clocks as always-on Lee Jones
2015-04-02 8:00 ` [STLinux Kernel] " Peter Griffin
2015-02-27 21:14 ` [PATCH 3/4] clk: Provide always-on clock support Lee Jones
2015-02-27 21:51 ` Lee Jones
2015-02-28 7:52 ` [STLinux Kernel] " Maxime Coquelin
2015-03-02 8:16 ` Lee Jones
2015-04-01 1:13 ` Michael Turquette
2015-02-28 9:21 ` Jassi Brar
2015-03-02 8:36 ` Lee Jones
2015-03-02 10:08 ` Jassi Brar
2015-03-02 10:18 ` Lee Jones
2015-03-02 10:25 ` Maxime Coquelin [this message]
2015-03-02 10:32 ` [STLinux Kernel] " Lee Jones
2015-03-02 10:28 ` Jassi Brar
2015-03-02 10:40 ` Lee Jones
2015-04-01 1:42 ` Michael Turquette
2015-04-02 4:39 ` Jassi Brar
2015-04-02 7:10 ` Lee Jones
2015-02-27 21:14 ` [PATCH 4/4] clk: dt: Introduce binding for " Lee Jones
2015-04-02 8:12 ` [STLinux Kernel] [PATCH 0/4] clk: Provide support for always-on clocks Peter Griffin
2015-04-02 9:45 ` Gabriel Fernandez
2015-04-02 10:53 ` Lee Jones
2015-04-02 10:58 ` Lee Jones
2015-04-02 10:52 ` Lee Jones
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