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SubjectRe: [PATCH v2 2/5] clocksource: timer-ti-dm: Implement cpu_pm notifier for context save and restore
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On 04/03/20 11:47 PM, Tony Lindgren wrote:
> * Lokesh Vutla <lokeshvutla@ti.com> [200304 04:45]:
>> Hi Tony,
>>
>> On 03/03/20 10:02 PM, Tony Lindgren wrote:
>>> Hi,
>>>
>>> * Lokesh Vutla <lokeshvutla@ti.com> [200228 09:55]:
>>>> omap_dm_timer_enable() restores the entire context(including counter)
>>>> based on 2 conditions:
>>>> - If get_context_loss_count is populated and context is lost.
>>>> - If get_context_loss_count is not populated update unconditionally.
>>>>
>>>> Case2 has a side effect of updating the counter register even though
>>>> context is not lost. When timer is configured in pwm mode, this is
>>>> causing undesired behaviour in the pwm period.
>>>>
>>>> Instead of using get_context_loss_count call back, implement cpu_pm
>>>> notifier with context save and restore support. And delete the
>>>> get_context_loss_count callback all together.
>>>
>>> Thanks for getting this going.
>>>
>>> I noticed system timers are not working properly now though. Not
>>
>> Can you provide me details on how you are testing and on which SoC?
>
> Hmm I guess with any SoC with gp timer as a clockevent as long as the
> system is idle enough for interrupts. I was seeing this at least on
> omap4, it may not show up with NFSroot because interrupts.
>
>> But context should be saved when awake is enabled. In this case how to make sure
>> the registers are accessible? Driver heavily uses pm_runtime calls for most
>> register access. When timer is running the register are made accessible but I am
>> worried about the case when timer is not running and trying to save context.
>>
>> Also in CLUSTER_PM_EXIT case, how to guarantee that registers are accessible?
>
> Well below is a version of your patch updated along the lines I described
> above. That's on top of the preparatory 1.5/2 patch I just sent for
> "clocksource: timer-ti-dm: Prepare for using cpuidle".
>
> It now seems to work for me bsed on quick testing. I have also not
> tested yet with the rest of the series. And we still need to run timer
> tests on some idle SoC.


Tested your changes on my BBB, timer and pwm are still working fine. Will repost
the series along with your changes.

Thanks and regards,
Lokesh

>
>>> For the OMAP_TIMER_ALWON checks, I believe am335x and am437x have
>>> OMAP_TIMER_ALWON set for timers but will still have context lost
>>> in deeper idle states as only the PMIC is enabled.
>>>
>>> For those cases, at least runtime_suspend and resume functions
>>> need to save and restore context based on setting some flag
>>> maybe based on of_machine_is_compatible() or soc_device_match().
>>
>> hmm..then it is better to not mark as alwon in case of am335x and am43xx no? I
>> don't see the flag being used for anything else other that context save and restore.
>
> Yeah or change the flag during runtime. But let's assume we have
> the flag properly set for this series.
>
> Regards,
>
> Tony
>
> 8< ------------------------
> From tony Mon Sep 17 00:00:00 2001
> From: Lokesh Vutla <lokeshvutla@ti.com>
> Date: Fri, 28 Feb 2020 15:23:43 +0530
> Subject: [PATCH] clocksource: timer-ti-dm: Implement cpu_pm notifier for
> context save and restore
>
> omap_dm_timer_enable() restores the entire context(including counter)
> based on 2 conditions:
> - If get_context_loss_count is populated and context is lost.
> - If get_context_loss_count is not populated update unconditionally.
>
> Case2 has a side effect of updating the counter register even though
> context is not lost. When timer is configured in pwm mode, this is
> causing undesired behaviour in the pwm period.
>
> Instead of using get_context_loss_count call back, implement cpu_pm
> notifier with context save and restore support. And delete the
> get_context_loss_count callback all together.
>
> Suggested-by: Tony Lindgren <tony@atomide.com>
> Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>
> [tony@atomide.com: removed pm_runtime calls from cpuidle calls]
> Signed-off-by: Tony Lindgren <tony@atomide.com>
> ---
> drivers/clocksource/timer-ti-dm.c | 99 ++++++++++++++++++-------------
> include/clocksource/timer-ti-dm.h | 3 +-
> 2 files changed, 60 insertions(+), 42 deletions(-)
>
> diff --git a/drivers/clocksource/timer-ti-dm.c b/drivers/clocksource/timer-ti-dm.c
> --- a/drivers/clocksource/timer-ti-dm.c
> +++ b/drivers/clocksource/timer-ti-dm.c
> @@ -20,6 +20,7 @@
>
> #include <linux/clk.h>
> #include <linux/clk-provider.h>
> +#include <linux/cpu_pm.h>
> #include <linux/module.h>
> #include <linux/io.h>
> #include <linux/device.h>
> @@ -92,6 +93,47 @@ static void omap_timer_restore_context(struct omap_dm_timer *timer)
> timer->context.tclr);
> }
>
> +static void omap_timer_save_context(struct omap_dm_timer *timer)
> +{
> + timer->context.tclr =
> + omap_dm_timer_read_reg(timer, OMAP_TIMER_CTRL_REG);
> + timer->context.twer =
> + omap_dm_timer_read_reg(timer, OMAP_TIMER_WAKEUP_EN_REG);
> + timer->context.tldr =
> + omap_dm_timer_read_reg(timer, OMAP_TIMER_LOAD_REG);
> + timer->context.tmar =
> + omap_dm_timer_read_reg(timer, OMAP_TIMER_MATCH_REG);
> + timer->context.tier = readl_relaxed(timer->irq_ena);
> + timer->context.tsicr =
> + omap_dm_timer_read_reg(timer, OMAP_TIMER_IF_CTRL_REG);
> +}
> +
> +static int omap_timer_context_notifier(struct notifier_block *nb,
> + unsigned long cmd, void *v)
> +{
> + struct omap_dm_timer *timer;
> +
> + timer = container_of(nb, struct omap_dm_timer, nb);
> +
> + switch (cmd) {
> + case CPU_CLUSTER_PM_ENTER:
> + if ((timer->capability & OMAP_TIMER_ALWON) ||
> + !atomic_read(&timer->enabled))
> + break;
> + omap_timer_save_context(timer);
> + break;
> + case CPU_CLUSTER_PM_ENTER_FAILED:
> + case CPU_CLUSTER_PM_EXIT:
> + if ((timer->capability & OMAP_TIMER_ALWON) ||
> + !atomic_read(&timer->enabled))
> + break;
> + omap_timer_restore_context(timer);
> + break;
> + }
> +
> + return NOTIFY_OK;
> +}
> +
> static int omap_dm_timer_reset(struct omap_dm_timer *timer)
> {
> u32 l, timeout = 100000;
> @@ -208,21 +250,7 @@ static int omap_dm_timer_set_source(struct omap_dm_timer *timer, int source)
>
> static void omap_dm_timer_enable(struct omap_dm_timer *timer)
> {
> - int c;
> -
> pm_runtime_get_sync(&timer->pdev->dev);
> -
> - if (!(timer->capability & OMAP_TIMER_ALWON)) {
> - if (timer->get_context_loss_count) {
> - c = timer->get_context_loss_count(&timer->pdev->dev);
> - if (c != timer->ctx_loss_count) {
> - omap_timer_restore_context(timer);
> - timer->ctx_loss_count = c;
> - }
> - } else {
> - omap_timer_restore_context(timer);
> - }
> - }
> }
>
> static void omap_dm_timer_disable(struct omap_dm_timer *timer)
> @@ -515,8 +543,6 @@ static int omap_dm_timer_start(struct omap_dm_timer *timer)
> omap_dm_timer_write_reg(timer, OMAP_TIMER_CTRL_REG, l);
> }
>
> - /* Save the context */
> - timer->context.tclr = l;
> return 0;
> }
>
> @@ -532,13 +558,6 @@ static int omap_dm_timer_stop(struct omap_dm_timer *timer)
>
> __omap_dm_timer_stop(timer, timer->posted, rate);
>
> - /*
> - * Since the register values are computed and written within
> - * __omap_dm_timer_stop, we need to use read to retrieve the
> - * context.
> - */
> - timer->context.tclr =
> - omap_dm_timer_read_reg(timer, OMAP_TIMER_CTRL_REG);
> omap_dm_timer_disable(timer);
> return 0;
> }
> @@ -561,9 +580,6 @@ static int omap_dm_timer_set_load(struct omap_dm_timer *timer, int autoreload,
> omap_dm_timer_write_reg(timer, OMAP_TIMER_LOAD_REG, load);
>
> omap_dm_timer_write_reg(timer, OMAP_TIMER_TRIGGER_REG, 0);
> - /* Save the context */
> - timer->context.tclr = l;
> - timer->context.tldr = load;
> omap_dm_timer_disable(timer);
> return 0;
> }
> @@ -585,9 +601,6 @@ static int omap_dm_timer_set_match(struct omap_dm_timer *timer, int enable,
> omap_dm_timer_write_reg(timer, OMAP_TIMER_MATCH_REG, match);
> omap_dm_timer_write_reg(timer, OMAP_TIMER_CTRL_REG, l);
>
> - /* Save the context */
> - timer->context.tclr = l;
> - timer->context.tmar = match;
> omap_dm_timer_disable(timer);
> return 0;
> }
> @@ -611,8 +624,6 @@ static int omap_dm_timer_set_pwm(struct omap_dm_timer *timer, int def_on,
> l |= trigger << 10;
> omap_dm_timer_write_reg(timer, OMAP_TIMER_CTRL_REG, l);
>
> - /* Save the context */
> - timer->context.tclr = l;
> omap_dm_timer_disable(timer);
> return 0;
> }
> @@ -634,8 +645,6 @@ static int omap_dm_timer_set_prescaler(struct omap_dm_timer *timer,
> }
> omap_dm_timer_write_reg(timer, OMAP_TIMER_CTRL_REG, l);
>
> - /* Save the context */
> - timer->context.tclr = l;
> omap_dm_timer_disable(timer);
> return 0;
> }
> @@ -649,9 +658,6 @@ static int omap_dm_timer_set_int_enable(struct omap_dm_timer *timer,
> omap_dm_timer_enable(timer);
> __omap_dm_timer_int_enable(timer, value);
>
> - /* Save the context */
> - timer->context.tier = value;
> - timer->context.twer = value;
> omap_dm_timer_disable(timer);
> return 0;
> }
> @@ -679,9 +685,6 @@ static int omap_dm_timer_set_int_disable(struct omap_dm_timer *timer, u32 mask)
> l = omap_dm_timer_read_reg(timer, OMAP_TIMER_WAKEUP_EN_REG) & ~mask;
> omap_dm_timer_write_reg(timer, OMAP_TIMER_WAKEUP_EN_REG, l);
>
> - /* Save the context */
> - timer->context.tier &= ~mask;
> - timer->context.twer &= ~mask;
> omap_dm_timer_disable(timer);
> return 0;
> }
> @@ -756,6 +759,12 @@ static int __maybe_unused omap_dm_timer_runtime_suspend(struct device *dev)
>
> atomic_set(&timer->enabled, 0);
>
> + if (timer->capability & OMAP_TIMER_ALWON ||
> + !timer->func_base)
> + return 0;
> +
> + omap_timer_save_context(timer);
> +
> return 0;
> }
>
> @@ -763,6 +772,10 @@ static int __maybe_unused omap_dm_timer_runtime_resume(struct device *dev)
> {
> struct omap_dm_timer *timer = dev_get_drvdata(dev);
>
> + if (!(timer->capability & OMAP_TIMER_ALWON) &&
> + timer->func_base)
> + omap_timer_restore_context(timer);
> +
> atomic_set(&timer->enabled, 1);
>
> return 0;
> @@ -838,7 +851,11 @@ static int omap_dm_timer_probe(struct platform_device *pdev)
> timer->id = pdev->id;
> timer->capability = pdata->timer_capability;
> timer->reserved = omap_dm_timer_reserved_systimer(timer->id);
> - timer->get_context_loss_count = pdata->get_context_loss_count;
> + }
> +
> + if (!(timer->capability & OMAP_TIMER_ALWON)) {
> + timer->nb.notifier_call = omap_timer_context_notifier;
> + cpu_pm_register_notifier(&timer->nb);
> }
>
> if (pdata)
> @@ -893,6 +910,8 @@ static int omap_dm_timer_remove(struct platform_device *pdev)
> list_for_each_entry(timer, &omap_timer_list, node)
> if (!strcmp(dev_name(&timer->pdev->dev),
> dev_name(&pdev->dev))) {
> + if (!(timer->capability & OMAP_TIMER_ALWON))
> + cpu_pm_unregister_notifier(&timer->nb);
> list_del(&timer->node);
> ret = 0;
> break;
> diff --git a/include/clocksource/timer-ti-dm.h b/include/clocksource/timer-ti-dm.h
> --- a/include/clocksource/timer-ti-dm.h
> +++ b/include/clocksource/timer-ti-dm.h
> @@ -110,13 +110,12 @@ struct omap_dm_timer {
> unsigned reserved:1;
> unsigned posted:1;
> struct timer_regs context;
> - int (*get_context_loss_count)(struct device *);
> - int ctx_loss_count;
> int revision;
> u32 capability;
> u32 errata;
> struct platform_device *pdev;
> struct list_head node;
> + struct notifier_block nb;
> };
>
> int omap_dm_timer_reserve_systimer(int id);
>

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