On Wed, 20 Jun 2018 09:11:19 +0200
Neil Armstrong <narmstrong@xxxxxxxxxxxx> wrote:
> Hi,
>
> On 20/06/2018 08:30, Tero Kristo wrote:
> > On 19/06/18 21:53, David Rivshin wrote:
> >> I think I've run across a regression in 4.16 that resulted from the TI clock
> >> infrastructure changes. A bisect pointed to [1] as the first breaking commit.
> >>
> >> Our use-case is a pwm-dmtimer-omap using timer7, with timer7_fck parented
> >> by clkdiv32k_ick (aka timer_32k_ck aka l4_per_cm:clk:0138:0). Starting with
> >> 4.16 that parenting fails in omap_dm_timer_set_source(), called from
> >> pwm_omap_dmtimer_probe, at this check:
> >> if (clk_hw_get_num_parents(__clk_get_hw(timer->fclk)) < 2)
> >> return 0;
> >> because timer->fclk is "l4_per_cm:clk:0068:0", whose only possible parent
> >> is "timer7_fck".
> >>
> >> It seemed to me that timer->fclk should instead be "timer7_fck" (which has
> >> the desired set of possible parents). I tried following the lead set in [2]
> >> and added "clocks" and "clock-names" properties on timer7. However, that
> >> resulted in omap_dm_timer_of_set_source(), called by omap_dm_timer_prepare(),
> >> failing when it tries to parent "timer7_fck" to itself.
> >>
> >> The following change in omap_dm_timer_prepare() does seem to work:
> >> - timer->fclk = clk_get(&timer->pdev->dev, "fck");
> >> + timer->fclk = clk_get_parent(clk_get(&timer->pdev->dev, "fck"));
> >
> > It seems omap_dm_timer_of_set_source() is actually completely broken and isn't doing anything useful. Neil, what was this function supposed to be doing, seeing you invented the initial patch for that (commit 31a7448f4fa8a528040e3df593e9781f55218183)?
>
> The original change was supposed to set the timer source clock by using the clock defined in the DT, but
> it was made to work when the code was in arch/arm and the fck was not found from DT.
>
>
> The omap_dm_timer_of_set_source() should be changed to get a specified clock name like "src":
> parent = clk_get(&timer->pdev->dev, "src");
> if (IS_ERR(parent))
> return -ENODEV;
>
> And the fck clock should be added to all timer nodes.
>
> For example ed839c3664cb308144fe70a3a95813ab59a03dfb or 521f9e5e3f871cdac3ecd2a583d14d0472278053 only adds fck to timer1/2, the 7 timers should have the fck clock.
>
> @David: chan you test the omap_dm_timer_of_set_source() change and in DT update the timer7 node with :
> clocks = <&timer7_fck>, <&clkdiv32k_ck>;
> clock-names = "fck", "src";
That didn't work as-is because clkdiv32k_ck isn't a direct parent of
timer7_fck anymore. However, if I change it to
<&l4_per_clkctrl AM3_CLKDIV32K_CLKCTRL 0>
then all seems well.
Since pwm-dmtimer-omap sets the source clock explicitly anyways
(based on the DT), using any of the parents of timer7_fck as
the timer7 "src" clock works in my case.
Also, if I leave off the "src" clock entirely, then omap_dm_timer_prepare()
defaults it to using that same clock:
rc = omap_dm_timer_of_set_source(timer);
if (rc == -ENODEV)
return omap_dm_timer_set_source(timer, OMAP_TIMER_SRC_32_KHZ);
and that also works for me.
Thanks,
David Rivshin
>
> Thanks,
> Neil
>
> >
> > -Tero
> >
> >> but I'm very uncertain whether that's the right path.
> >> Should omap_dm_timer know that the clock returned is actually a child of the
> >> clock it's interested in? Or should clk_get(<timerN>,"fck") be returning the
> >> timerN_fck in the first place? Or is the problem something else entirely?
> >>
> >> As I'm not sure how these pieces are all intended to fit together, any
> >> pointers would be appreciated.
> >>
> >> Thanks,
> >> David Rivshin
> >>
> >> [1] df54bfc5502a ("clk: ti: am33xx: add clkctrl clock data")
> >> https://www.spinics.net/lists/linux-omap/msg139798.html
> >> [2] 521f9e5e3f87 ("ARM: dts: am33xx: add fck under timers1/2")
> >> https://www.spinics.net/lists/linux-omap/msg140605.html
> >>
> >
> > --
> > Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
>
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