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

Dmitry Osipenko
2019-06-14T12:01:23Z

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.