On Fri, Nov 04, 2022 at 04:51:23PM +0100, Maxime Ripard wrote:
> Just filling determine_rate if it's missing with
> __clk_mux_determine_rate will possibly pick different parents, and I'm
> fairly certain that this have never been tested on most platforms, and
> will be completely broken. And I don't really want to play a game of
> whack-a-mole adding that flag everywhere it turns out it's broken.
Well, hopefully everyone for whom it's an issue currently will be
objecting to this version of the change anyway so we'll either know
where to set the flag or we'll get the whack-a-mole with the series
being merged?
Hi Mark,
On Fri, Nov 04, 2022 at 03:59:53PM +0000, Mark Brown wrote:
> On Fri, Nov 04, 2022 at 04:51:23PM +0100, Maxime Ripard wrote:
>
> > Just filling determine_rate if it's missing with
> > __clk_mux_determine_rate will possibly pick different parents, and I'm
> > fairly certain that this have never been tested on most platforms, and
> > will be completely broken. And I don't really want to play a game of
> > whack-a-mole adding that flag everywhere it turns out it's broken.
>
> Well, hopefully everyone for whom it's an issue currently will be
> objecting to this version of the change anyway so we'll either know
> where to set the flag or we'll get the whack-a-mole with the series
> being merged?
I'm sorry, I'm not sure what you mean here. The only issue to fix at the
moment is that determine_rate and set_parent aren't coupled, and it led
to issues due to oversight.
I initially added a warning but Stephen wanted to fix all users in that
case and make that an error instead.
If I filled __clk_mux_determine_rate into clocks that weren't using it
before, I would change their behavior. With that flag set, on all users
I add __clk_mux_determine_rate to, the behavior is the same than what we
previously had, so the risk of regressions is minimal, and everything
should keep going like it was?
Maxime
On Mon, Nov 07, 2022 at 09:43:22AM +0100, Maxime Ripard wrote:
> On Fri, Nov 04, 2022 at 03:59:53PM +0000, Mark Brown wrote:
> > Well, hopefully everyone for whom it's an issue currently will be
> > objecting to this version of the change anyway so we'll either know
> > where to set the flag or we'll get the whack-a-mole with the series
> > being merged?
> I'm sorry, I'm not sure what you mean here. The only issue to fix at the
> moment is that determine_rate and set_parent aren't coupled, and it led
> to issues due to oversight.
> I initially added a warning but Stephen wanted to fix all users in that
> case and make that an error instead.
My suggestion is that instead of doing either of these things it'd be
quicker and less error prone to just fix the core to provide the default
implementation if nothing more specific is provided. Any issues that
causes would already be present with your current series.
> If I filled __clk_mux_determine_rate into clocks that weren't using it
> before, I would change their behavior. With that flag set, on all users
> I add __clk_mux_determine_rate to, the behavior is the same than what we
> previously had, so the risk of regressions is minimal, and everything
> should keep going like it was?
The series does fill in __clk_mux_determine_rate for everything though -
if it was just assumed by default the only thing that'd be needed would
be adding the flag.
On Mon, Nov 07, 2022 at 12:06:07PM +0000, Mark Brown wrote:
> On Mon, Nov 07, 2022 at 09:43:22AM +0100, Maxime Ripard wrote:
> > On Fri, Nov 04, 2022 at 03:59:53PM +0000, Mark Brown wrote:
>
> > > Well, hopefully everyone for whom it's an issue currently will be
> > > objecting to this version of the change anyway so we'll either know
> > > where to set the flag or we'll get the whack-a-mole with the series
> > > being merged?
>
> > I'm sorry, I'm not sure what you mean here. The only issue to fix at the
> > moment is that determine_rate and set_parent aren't coupled, and it led
> > to issues due to oversight.
>
> > I initially added a warning but Stephen wanted to fix all users in that
> > case and make that an error instead.
>
> My suggestion is that instead of doing either of these things it'd be
> quicker and less error prone to just fix the core to provide the default
> implementation if nothing more specific is provided. Any issues that
> causes would already be present with your current series.
>
> > If I filled __clk_mux_determine_rate into clocks that weren't using it
> > before, I would change their behavior. With that flag set, on all users
> > I add __clk_mux_determine_rate to, the behavior is the same than what we
> > previously had, so the risk of regressions is minimal, and everything
> > should keep going like it was?
>
> The series does fill in __clk_mux_determine_rate for everything though -
> if it was just assumed by default the only thing that'd be needed would
> be adding the flag.
The behavior assumed by default was equivalent to
__clk_mux_determine_rate + CLK_SET_RATE_NO_REPARENT. We could indeed set
both if determine_rate is missing in the core, but that's unprecedented
in the clock framework so I think we'll want Stephen to comment here :)
It's also replacing one implicit behavior by another. The point of this
series was to raise awareness on that particular point, so I'm not sure
it actually fixes things. We'll see what Stephen thinks about it.
Maxime
On Mon, Nov 07, 2022 at 04:26:03PM +0100, Maxime Ripard wrote:
> On Mon, Nov 07, 2022 at 12:06:07PM +0000, Mark Brown wrote:
> > On Mon, Nov 07, 2022 at 09:43:22AM +0100, Maxime Ripard wrote:
> > The series does fill in __clk_mux_determine_rate for everything though -
> > if it was just assumed by default the only thing that'd be needed would
> > be adding the flag.
> The behavior assumed by default was equivalent to
> __clk_mux_determine_rate + CLK_SET_RATE_NO_REPARENT. We could indeed set
> both if determine_rate is missing in the core, but that's unprecedented
> in the clock framework so I think we'll want Stephen to comment here :)
> It's also replacing one implicit behavior by another. The point of this
> series was to raise awareness on that particular point, so I'm not sure
> it actually fixes things. We'll see what Stephen thinks about it.
We could also just set the operation and still require the flag to be
specified. I'm a little surprised to learn that it's something you
might want to override, never mind that the API didn't have a default -
it feels like a bit of a landmine that this is the case and is probably
why there's so many cases to fix up.