Re: [PATCH 2/2] rtc: tegra: Implement suspend clock source

Thierry Reding
2019-06-14T13:41:17Z

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On Fri, Jun 14, 2019 at 03:01:13PM +0300, Dmitry Osipenko wrote:
> 14.06.2019 13:47, Thierry Reding пишет:
> > From: Thierry Reding <treding@nvidia.com>
> >
> > The suspend clock source for Tegra210 and earlier is currently
> > implemented in the Tegra timer driver. However, the suspend clock source
> > code accesses registers that are part of the RTC hardware block, so both
> > can step on each others' toes. In practice this isn't an issue, but
> > there is no reason why the RTC driver can't implement the clock source,
> > so move the code over to the tegra-rtc driver.
> >
> > Signed-off-by: Thierry Reding <treding@nvidia.com>
> > ---
> > drivers/clocksource/timer-tegra.c | 44 -------------------------------
> > drivers/rtc/rtc-tegra.c | 42 +++++++++++++++++++++++++++++
> > 2 files changed, 42 insertions(+), 44 deletions(-)
> >
> > diff --git a/drivers/clocksource/timer-tegra.c b/drivers/clocksource/timer-tegra.c
> > index e6608141cccb..87eac618924d 100644
> > --- a/drivers/clocksource/timer-tegra.c
> > +++ b/drivers/clocksource/timer-tegra.c
> > @@ -21,10 +21,6 @@
> >
> > #include "timer-of.h"
> >
> > -#define RTC_SECONDS 0x08
> > -#define RTC_SHADOW_SECONDS 0x0c
> > -#define RTC_MILLISECONDS 0x10
> > -
> > #define TIMERUS_CNTR_1US 0x10
> > #define TIMERUS_USEC_CFG 0x14
> > #define TIMERUS_CNTR_FREEZE 0x4c
> > @@ -164,34 +160,6 @@ static struct delay_timer tegra_delay_timer = {
> > };
> > #endif
> >
> > -static struct timer_of suspend_rtc_to = {
> > - .flags = TIMER_OF_BASE | TIMER_OF_CLOCK,
> > -};
> > -
> > -/*
> > - * tegra_rtc_read - Reads the Tegra RTC registers
> > - * Care must be taken that this function is not called while the
> > - * tegra_rtc driver could be executing to avoid race conditions
> > - * on the RTC shadow register
> > - */
> > -static u64 tegra_rtc_read_ms(struct clocksource *cs)
> > -{
> > - void __iomem *reg_base = timer_of_base(&suspend_rtc_to);
> > -
> > - u32 ms = readl_relaxed(reg_base + RTC_MILLISECONDS);
> > - u32 s = readl_relaxed(reg_base + RTC_SHADOW_SECONDS);
> > -
> > - return (u64)s * MSEC_PER_SEC + ms;
> > -}
> > -
> > -static struct clocksource suspend_rtc_clocksource = {
> > - .name = "tegra_suspend_timer",
> > - .rating = 200,
> > - .read = tegra_rtc_read_ms,
> > - .mask = CLOCKSOURCE_MASK(32),
> > - .flags = CLOCK_SOURCE_IS_CONTINUOUS | CLOCK_SOURCE_SUSPEND_NONSTOP,
> > -};
> > -
> > static inline unsigned int tegra_base_for_cpu(int cpu, bool tegra20)
> > {
> > if (tegra20) {
> > @@ -385,15 +353,3 @@ static int __init tegra20_init_timer(struct device_node *np)
> > return tegra_init_timer(np, true, rating);
> > }
> > TIMER_OF_DECLARE(tegra20_timer, "nvidia,tegra20-timer", tegra20_init_timer);
> > -
> > -static int __init tegra20_init_rtc(struct device_node *np)
> > -{
> > - int ret;
> > -
> > - ret = timer_of_init(np, &suspend_rtc_to);
> > - if (ret)
> > - return ret;
> > -
> > - return clocksource_register_hz(&suspend_rtc_clocksource, 1000);
> > -}
> > -TIMER_OF_DECLARE(tegra20_rtc, "nvidia,tegra20-rtc", tegra20_init_rtc);
> > diff --git a/drivers/rtc/rtc-tegra.c b/drivers/rtc/rtc-tegra.c
> > index 8fa1b3febf69..6da54264a27a 100644
> > --- a/drivers/rtc/rtc-tegra.c
> > +++ b/drivers/rtc/rtc-tegra.c
> > @@ -6,6 +6,7 @@
> > */
> >
> > #include <linux/clk.h>
> > +#include <linux/clocksource.h>
> > #include <linux/delay.h>
> > #include <linux/init.h>
> > #include <linux/io.h>
> > @@ -52,8 +53,15 @@ struct tegra_rtc_info {
> > struct clk *clk;
> > int irq; /* alarm and periodic IRQ */
> > spinlock_t lock;
> > +
> > + struct clocksource clksrc;
> > };
> >
> > +static struct tegra_rtc_info *to_tegra_rtc(struct clocksource *clksrc)
> > +{
> > + return container_of(clksrc, struct tegra_rtc_info, clksrc);
> > +}
> > +
> > /*
> > * RTC hardware is busy when it is updating its values over AHB once every
> > * eight 32 kHz clocks (~250 us). Outside of these updates the CPU is free to
> > @@ -268,6 +276,17 @@ static const struct rtc_class_ops tegra_rtc_ops = {
> > .alarm_irq_enable = tegra_rtc_alarm_irq_enable,
> > };
> >
> > +static u64 tegra_rtc_read_ms(struct clocksource *clksrc)
> > +{
> > + struct tegra_rtc_info *info = to_tegra_rtc(clksrc);
> > + u32 ms, s;
> > +
> > + ms = readl_relaxed(info->base + TEGRA_RTC_REG_MILLI_SECONDS);
> > + s = readl_relaxed(info->base + TEGRA_RTC_REG_SHADOW_SECONDS);
> > +
> > + return (u64)s * MSEC_PER_SEC + ms;
> > +}
> > +
> > static const struct of_device_id tegra_rtc_dt_match[] = {
> > { .compatible = "nvidia,tegra20-rtc", },
> > {}
> > @@ -339,6 +358,28 @@ static int tegra_rtc_probe(struct platform_device *pdev)
> > goto disable_clk;
> > }
> >
> > + /*
> > + * The Tegra RTC is the only reliable clock source that persists
> > + * across an SC7 transition (VDD_CPU and VDD_CORE off) on Tegra210
> > + * and earlier. Starting with Tegra186, the ARM v8 architected timer
> > + * is in an always on power partition and its reference clock keeps
> > + * running during SC7. Therefore, we technically don't need to have
> > + * the RTC register as a clock source on Tegra186 and later, but it
> > + * doesn't hurt either, so we just register it unconditionally here.
> > + */
> > + info->clksrc.name = "tegra_rtc";
> > + info->clksrc.rating = 200;
> > + info->clksrc.read = tegra_rtc_read_ms;
> > + info->clksrc.mask = CLOCKSOURCE_MASK(32);
>
> Hm.. shouldn't this be CLOCKSOURCE_MASK(52)? Given that there are 32 bits for seconds and
> 10bits for milliseconds.

Did you mean to say CLOCKSOURCE_MASK(42)? Yeah, that's probably better
here.

Thierry

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