From: james.hogan@imgtec•com (James Hogan)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v5 4/5] clk: add CLK_SET_RATE_NO_REPARENT flag
Date: Thu, 25 Jul 2013 13:55:09 +0100 [thread overview]
Message-ID: <51F1202D.9060403@imgtec.com> (raw)
In-Reply-To: <51F11B46.7010900@samsung.com>
Hi Sylwester
On 25/07/13 13:34, Sylwester Nawrocki wrote:
> On 06/13/2013 06:06 PM, James Hogan wrote:
>> Add a CLK_SET_RATE_NO_REPARENT clock flag, which will prevent muxes
>> being reparented during clk_set_rate.
>>
>> To avoid breaking existing platforms, all callers of clk_register_mux()
>> are adjusted to pass the new flag. Platform maintainers are encouraged
>> to remove the flag if they wish to allow mux reparenting on set_rate.
> [..]
>> Changes in v3:
>>
>> * rename/invert CLK_SET_RATE_REMUX to CLK_SET_RATE_NO_REPARENT and move
>> to this new patch.
>> * patch 3: add CLK_SET_RATE_NO_REPARENT flag to all callers of
>> clk_register_mux. If you don't mind your clocks being reparented in
>> response to set_rate please let me know and I'll drop the relevant
>> portion of the patch.
>
> Why is this better to change current behaviour of the clock core
> and modify all drivers instead of having, e.g. CLK_SET_RATE_REPARENT
> set in drivers of hardware that supports clock re-parenting while
> setting clock rate ?
See this message from Mike Turquette which first suggested it:
http://marc.info/?l=linux-kernel&m=136847508109344&w=2
> Is there intention to just have the automatic clock re-parenting
> as a default feature in the common clock API ?
Yes, that would be the result (except where explicitly disallowed).
Unfortunately where such policy should ideally be defined is still up in
the air.
It's not a property of the hardware, but then it is arguably a property
of the environment the bootloader has configured (like the stuff in the
/chosen device tree node).
Presuming that the usual reason not to reparent a mux is because other
important clocks depend on it, the kernel might know enough to work out
whether it's safe (unless of course there are other cores/threads in the
SoC using the clock that Linux isn't aware of, which brings us back to
it being a bootloader environment thing).
> My apologies if this has already been answered, I haven't been
> following this thread.
No problem :)
Cheers
James
next prev parent reply other threads:[~2013-07-25 12:55 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-13 16:05 [PATCH v5 0/5] clk: implement remuxing during set_rate James Hogan
2013-06-13 16:05 ` [PATCH v5 1/5] clk: abstract parent cache James Hogan
2013-06-13 16:05 ` [PATCH v5 2/5] clk: move some parent related functions upwards James Hogan
2013-06-13 16:06 ` [PATCH v5 3/5] clk: add support for clock reparent on set_rate James Hogan
2013-06-13 16:06 ` [PATCH v5 4/5] clk: add CLK_SET_RATE_NO_REPARENT flag James Hogan
2013-07-25 12:34 ` Sylwester Nawrocki
2013-07-25 12:55 ` James Hogan [this message]
2013-07-25 18:05 ` Mike Turquette
2013-06-13 16:06 ` [PATCH v5 5/5] clk: clk-mux: implement remuxing on set_rate James Hogan
2013-06-21 17:04 ` [PATCH v5 0/5] clk: implement remuxing during set_rate Mike Turquette
2013-06-21 21:27 ` James Hogan
2013-07-24 18:39 ` Stephen Boyd
2013-07-25 9:07 ` James Hogan
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