Messages in this thread Patch in this message |  | | Subject | Re: [PATCH 1/3] clocksource: davinci: work around a clocksource problem on dm365 SoC | From | David Lechner <> | Date | Mon, 16 Dec 2019 11:58:31 -0600 |
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On 12/13/19 10:24 AM, Bartosz Golaszewski wrote: > From: Bartosz Golaszewski <bgolaszewski@baylibre.com> > > The DM365 platform has a strange quirk (only present when using ancient > u-boot - mainline u-boot v2013.01 and later works fine) where if we > enable the second half of the timer in periodic mode before we do its > initialization - the time won't start flowing and we can't boot. > > When using more recent u-boot, we can enable the timer, then reinitialize > it and all works fine. > > I've been unable to figure out why that is, but a workaround for this > is straightforward - just cache the enable bits for tim34.
I had a hard time groking this code. See suggested changes below for something that would make the intention more clear (to me at least).
> > Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com> > --- > drivers/clocksource/timer-davinci.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/drivers/clocksource/timer-davinci.c b/drivers/clocksource/timer-davinci.c > index 62745c962049..1c22443acaeb 100644 > --- a/drivers/clocksource/timer-davinci.c > +++ b/drivers/clocksource/timer-davinci.c > @@ -64,6 +64,8 @@ static struct { > unsigned int tim_off; > } davinci_clocksource; > > +static unsigned int davinci_clocksource_tim32_mode;
static unsigned bool davinci_clocksource_initialized;
> + > static struct davinci_clockevent * > to_davinci_clockevent(struct clock_event_device *clockevent) > { > @@ -94,7 +96,7 @@ static void davinci_tim12_shutdown(void __iomem *base) > * halves. In this case TIM34 runs in periodic mode and we must > * not modify it. > */ > - tcr |= DAVINCI_TIMER_ENAMODE_PERIODIC << > + tcr |= davinci_clocksource_tim32_mode << > DAVINCI_TIMER_ENAMODE_SHIFT_TIM34;
if (davinci_clocksource_initialized) tcr |= DAVINCI_TIMER_ENAMODE_PERIODIC << DAVINCI_TIMER_ENAMODE_SHIFT_TIM34;
> > writel_relaxed(tcr, base + DAVINCI_TIMER_REG_TCR); > @@ -107,7 +109,7 @@ static void davinci_tim12_set_oneshot(void __iomem *base) > tcr = DAVINCI_TIMER_ENAMODE_ONESHOT << > DAVINCI_TIMER_ENAMODE_SHIFT_TIM12; > /* Same as above. */ > - tcr |= DAVINCI_TIMER_ENAMODE_PERIODIC << > + tcr |= davinci_clocksource_tim32_mode << > DAVINCI_TIMER_ENAMODE_SHIFT_TIM34;
if (davinci_clocksource_initialized) tcr |= DAVINCI_TIMER_ENAMODE_PERIODIC << DAVINCI_TIMER_ENAMODE_SHIFT_TIM34;
> > writel_relaxed(tcr, base + DAVINCI_TIMER_REG_TCR); > @@ -206,6 +208,8 @@ static void davinci_clocksource_init_tim34(void __iomem *base) > writel_relaxed(0x0, base + DAVINCI_TIMER_REG_TIM34); > writel_relaxed(UINT_MAX, base + DAVINCI_TIMER_REG_PRD34); > writel_relaxed(tcr, base + DAVINCI_TIMER_REG_TCR); > + > + davinci_clocksource_tim32_mode = DAVINCI_TIMER_ENAMODE_PERIODIC;
davinci_clocksource_initialized = true;
> } > > /* >
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