[PATCH] clk: Propagate clk_set_rate() if CLK_SET_PARENT_RATE present

[Sam Protsenko]

On Wed, Jul 3, 2024 at 10:00 AM Michael Nazzareno Trimarchi
<michael at amarulasolutions.com> wrote:
>
> Hi all
>
> Working on the clock now. I have done a different implementation
>
> clk-mux, clk-gate I have added a clk_generic_set_rate that is a stub
> that propagate to the parent, I think that should work the same but
> wihout this while and even on preparation on more
> changes I need. Can be work on your case too?
>

Hi Michael,

I've provided some thoughts on your gate/mux implementation here: [1].
As you've submitted your (different) implementation of the same
feature, but 4 months later, I guess my patch doesn't cover your
cases, or perhaps it has some design flaws? Please let me know.

If anything, that shows there is a rising need in this propagation
feature. I'd like to encourage the maintainers to take a look at both
implementations, and maybe at least comment on why there is hesitance
to accept this patch. It's been almost 5 months that I'm trying to
push that through, and my MMC work (DDR mode on E850-96 board to be
precise) still very much depends on this.

Thanks!

[1] https://lists.denx.de/pipermail/u-boot/2024-July/559753.html


> Michael
>
> On Thu, Jun 13, 2024 at 5:33 PM Tom Rini <trini at konsulko.com> wrote:
> >
> > On Mon, Jun 10, 2024 at 02:43:17PM -0500, Sam Protsenko wrote:
> > > On Tue, May 14, 2024 at 3:26 PM Sam Protsenko
> > > <semen.protsenko at linaro.org> wrote:
> > > >
> > > > On Wed, May 1, 2024 at 4:12 PM Sam Protsenko <semen.protsenko at linaro.org> wrote:
> > > > >
> > > > > On Wed, Apr 10, 2024 at 9:53 PM Sean Anderson <seanga2 at gmail.com> wrote:
> > > > > >
> > > > > > On 3/7/24 19:04, Sam Protsenko wrote:
> > > > > > > Sometimes clocks provided to a consumer might not have .set_rate
> > > > > > > operation (like gate or mux clocks), but have CLK_SET_PARENT_RATE flag
> > > > > > > set. In that case it's usually possible to find a parent up the tree
> > > > > > > which is capable of setting the rate (div, pll, etc). Implement a simple
> > > > > > > lookup procedure for such cases, to traverse the clock tree until
> > > > > > > .set_rate capable parent is found, and use that parent to actually
> > > > > > > change the rate. The search will stop once the first .set_rate capable
> > > > > > > clock is found, which is usually enough to handle most cases.
> > > > > > >
> > > > > > > Signed-off-by: Sam Protsenko <semen.protsenko at linaro.org>
> > > > > > > ---
> > > > >
> > > > > [snip]
> > > > >
> > > > > >
> > > > > > Can you give an example of where this is needed?
> > > > > >
> > > > >
> > > > > Sure. In my case it's needed for eMMC enablement on E850-96 board.
> > > > > eMMC node in the device tree [1] is a gate clock
> > > > > (CLK_GOUT_MMC_EMBD_SDCLKIN), so the MMC driver won't be able to change
> > > > > its rate. But that clock actually has CLK_SET_RATE_PARENT flag set in
> > > > > the clock driver [2]. So the right thing to do in this case (and
> > > > > that's basically how it's done in Linux kernel too) is to traverse the
> > > > > clock tree upwards, and try to find the parent capable to do .set_rate
> > > > > (which is usually a divider clock), and use it to change the clock
> > > > > rate. I'm working on exynos_dw_mmc driver [3] right now, making it use
> > > > > CCF clocks, but I can't do that before this patch is applied.
> > > > >
> > > > > Grepping the U-Boot tree I can see the CLK_SET_RATE_PARENT flag is
> > > > > also used in various IMX clock drivers and STM32MP13 clock driver. I
> > > > > guess without this change those flags will be basically ignored.
> > > > >
> > > > > Thanks!
> > > > >
> > > >
> > > > Hi Sean,
> > > >
> > > > Just wanted to check if you think my explanation above is ok and the
> > > > patch can be applied? I'm finishing my new patch series for enabling
> > > > MMC on E850-96, but this patch has to be applied first.
> > > >
> > > > Thanks!
> > > >
> > >
> > > Hi Tom,
> > >
> > > Would it be reasonable to ask you to take care of this patch? It's
> > > been ignored for 3 months now, but it's needed for eMMC enablement on
> > > E850-96 board.
> >
> > Any comments at this point Sean?
> >
> > --
> > Tom
>
>
>
> --
> Michael Nazzareno Trimarchi
> Co-Founder & Chief Executive Officer
> M. +39 347 913 2170
> michael at amarulasolutions.com
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