[PATCH 04/31] clk: add clk_round_rate()
seanga2 at gmail.com
Sat Aug 29 23:50:40 CEST 2020
On 8/29/20 5:48 PM, Sean Anderson wrote:
> On 8/29/20 5:20 PM, Simon Glass wrote:
>> Hi Dario,
>> +Stephen Warren
>> On Tue, 25 Aug 2020 at 03:24, Dario Binacchi <dariobin at libero.it> wrote:
>>> It returns the rate which will be set if you ask clk_set_rate() to set
>>> that rate. It provides a way to query exactly what rate you'll get if
>>> you call clk_set_rate() with that same argument.
>>> So essentially, clk_round_rate() and clk_set_rate() are equivalent
>>> except the former does not modify the clock hardware in any way.
>>> Signed-off-by: Dario Binacchi <dariobin at libero.it>
>>> arch/sandbox/include/asm/clk.h | 9 +++++++++
>>> drivers/clk/clk-uclass.c | 15 +++++++++++++++
>>> drivers/clk/clk_sandbox.c | 17 +++++++++++++++++
>>> drivers/clk/clk_sandbox_test.c | 10 ++++++++++
>>> include/clk-uclass.h | 8 ++++++++
>>> include/clk.h | 29 +++++++++++++++++++++++++++++
>>> test/dm/clk.c | 22 ++++++++++++++++++++++
>>> 7 files changed, 110 insertions(+)
>> Reviewed-by: Simon Glass <sjg at chromium.org>
>> But I wonder if we should change the set_rate() uclass interface to
>> have a flag value, one of the flags being 'dry run' which doesn't
>> actually set the value?
>> You would still have the same call to the uclass functions
>> clk_set_rate() and clk_round_rate() but the driver API would implement
>> both with calls to set_rate()?
> Linux uses separate clk_ops functions for this purpose
>> * @recalc_rate Recalculate the rate of this clock, by querying hardware. The
>> * parent rate is an input parameter. It is up to the caller to
>> * ensure that the prepare_mutex is held across this call.
>> * Returns the calculated rate. Optional, but recommended - if
>> * this op is not set then clock rate will be initialized to 0.
err, I meant to quote
> * @round_rate: Given a target rate as input, returns the closest rate actually
> * supported by the clock. The parent rate is an input/output
> * parameter.
>> long (*round_rate)(struct clk_hw *hw, unsigned long rate,
>> unsigned long *parent_rate);
> Besides matching their interface, I think there is good reason for
> keeping these functions separate. Existing clock drivers would need to
> be rewritten so they don't set the clock rate when you just want to do a
> dry run. This way, it's very clear when a driver supports recalc_rate.
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