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

Dmitry Osipenko
2019-06-14T13:49:53Z

14.06.2019 16:41, Thierry Reding пишет:
> 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.

Yes, 42 :)