Hi,
On 09/01/2014 12:20 PM, Maxime Ripard wrote:
> Hi,
>
> On Sun, Aug 31, 2014 at 12:15:50PM +0200, Hans de Goede wrote:
>> Hi,
>>
>> On 08/30/2014 10:03 PM, Maxime Ripard wrote:
>>> The current phase API doesn't look into the actual hardware to get the phase
>>> value, but will rather get it from a variable only set by the set_phase
>>> function.
>>>
>>> This will cause issue when the client driver will never call the set_phase
>>> function, where we can end up having a reported phase that will not match what
>>> the hardware has been programmed to by the bootloader or what phase is
>>> programmed out of reset.
>>>
>>> Add a new get_phase function for the drivers to implement so that we can get
>>> this value.
>>>
>>> Signed-off-by: Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx>
>>> ---
>>> drivers/clk/clk.c | 17 ++++++++++++++---
>>> include/linux/clk-provider.h | 5 +++++
>>> 2 files changed, 19 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
>>> index d87661af0c72..7dbceca694f1 100644
>>> --- a/drivers/clk/clk.c
>>> +++ b/drivers/clk/clk.c
>>> @@ -1797,8 +1797,8 @@ out:
>>> * clk_get_phase - return the phase shift of a clock signal
>>> * @clk: clock signal source
>>> *
>>> - * Returns the phase shift of a clock node in degrees, otherwise returns
>>> - * -EERROR.
>>> + * Returns the phase shift of a clock node in degrees. Any negative
>>> + * values are errors.
>>> */
>>> int clk_get_phase(struct clk *clk)
>>> {
>>> @@ -1808,7 +1808,18 @@ int clk_get_phase(struct clk *clk)
>>> goto out;
>>>
>>> clk_prepare_lock();
>>> - ret = clk->phase;
>>> +
>>> + if (clk->phase) {
>>> + ret = clk->phase;
>>> + goto out_unlock;
>>> + }
>>
>> 0 is a valid phase, so this will cause the phase to
>> be read from the hardware each time if the phase is 0.
>>
>> Perhaps make clk->phase signed (if it is not already), init it
>> to -1, and check for it not being -1 ?
>
> Yeah, I'm not really proud of this code either, but yours would expose
> this -1 into debugfs, so I'm not sure it's really better :)
>
> (with -1 being a valid phase too)
According to the comments in the patch adding the original phase functions
valid values are 0 - 359. And you could use clk_get_phase from the debugfs
code.
Regards,
Hans
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