Date:   Wed, 4 Mar 2020 18:13:42 -0600
From:   Suman Anna <s-anna@...com>
To:     Mathieu Poirier <mathieu.poirier@...aro.org>,
        Tero Kristo <t-kristo@...com>
CC:     <bjorn.andersson@...aro.org>, <ohad@...ery.com>,
        <linux-remoteproc@...r.kernel.org>, <afd@...com>,
        <linux-kernel@...r.kernel.org>, <linux-omap@...r.kernel.org>
Subject: Re: [PATCHv7 12/15] remoteproc/omap: Add support for runtime
 auto-suspend/resume

On 3/4/20 3:35 PM, Mathieu Poirier wrote:
> On Fri, Feb 21, 2020 at 12:19:33PM +0200, Tero Kristo wrote:
>> From: Suman Anna <s-anna@...com>
>>
>> This patch enhances the PM support in the OMAP remoteproc driver to
>> support the runtime auto-suspend. A remoteproc may not be required to
>> be running all the time, and typically will need to be active only
>> during certain usecases. As such, to save power, it should be turned
>> off during potential long periods of inactivity between usecases.
>> This suspend and resume of the device is a relatively heavy process
>> in terms of latencies, so a remoteproc should be suspended only after
>> a certain period of prolonged inactivity. The OMAP remoteproc driver
>> leverages the runtime pm framework's auto_suspend feature to accomplish
>> this functionality. This feature is automatically enabled when a remote
>> processor has successfully booted. The 'autosuspend_delay_ms' for each
>> device dictates the inactivity period/time to wait for before
>> suspending the device.
>>
>> The runtime auto-suspend design relies on marking the last busy time
>> on every communication (virtqueue kick) to and from the remote processor.
>> When there has been no activity for 'autosuspend_delay_ms' time, the
>> runtime PM framework invokes the driver's runtime pm suspend callback
>> to suspend the device. The remote processor will be woken up on the
>> initiation of the next communication message through the runtime pm
>> resume callback. The current auto-suspend design also allows a remote
>> processor to deny a auto-suspend attempt, if it wishes to, by sending a
>> NACK response to the initial suspend request message sent to the remote
>> processor as part of the suspend process. The auto-suspend request is
>> also only attempted if the remote processor is idled and in standby at
>> the time of inactivity timer expiry. This choice is made to avoid
>> unnecessary messaging, and the auto-suspend is simply rescheduled to
>> be attempted again after a further lapse of autosuspend_delay_ms.
>>
>> The runtime pm callbacks functionality in this patch reuses most of the
>> core logic from the suspend/resume support code, and make use of an
>> additional auto_suspend flag to differentiate the logic in common code
>> from system suspend. The system suspend/resume sequences are also updated
>> to reflect the proper pm_runtime statuses, and also to really perform a
>> suspend/resume only if the remoteproc has not been auto-suspended at the
>> time of request. The remote processor is left in suspended state on a
>> system resume if it has been auto-suspended before, and will be woken up
>> only when a usecase needs to run.
>>
>> The OMAP remoteproc driver currently uses a default value of 10 seconds
>> for all OMAP remoteprocs, and a different value can be chosen either by
>> choosing a positive value for the 'ti,autosuspend-delay-ms' under DT or
>> by updating the 'autosuspend_delay_ms' field at runtime through the
>> sysfs interface. A negative value is equivalent to disabling the runtime
>> suspend.
>>     Eg: To use 25 seconds for IPU2 on DRA7xx,
>>       echo 25000 > /sys/bus/platform/devices/55020000.ipu/power/autosuspend_delay_ms
>>
>> The runtime suspend feature can also be similarly enabled or disabled by
>> writing 'auto' or 'on' to the device's 'control' power field. The default
>> is enabled.
>>     Eg: To disable auto-suspend for IPU2 on DRA7xx SoC,
>>       echo on > /sys/bus/platform/devices/55020000.ipu/power/control
>>
>> Signed-off-by: Suman Anna <s-anna@...com>
>> [t-kristo@...com: converted to use ti-sysc instead of hwmod]
>> Signed-off-by: Tero Kristo <t-kristo@...com>
>> ---
>> v7:
>>   - fixed the broken behavior for timers during runtime suspend
>>   - revamped the runtime PM handling code back towards the initial
>>     implementation, Suman reported some issues which seemed to have
>>     been introduced by my attempts to clean-up the code a bit.
>>
>>  drivers/remoteproc/omap_remoteproc.c | 202 +++++++++++++++++++++++++--
>>  1 file changed, 193 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/remoteproc/omap_remoteproc.c b/drivers/remoteproc/omap_remoteproc.c
>> index 0d45af1fb0e3..1ac270df4d66 100644
>> --- a/drivers/remoteproc/omap_remoteproc.c
>> +++ b/drivers/remoteproc/omap_remoteproc.c
>> @@ -22,6 +22,7 @@
>>  #include <linux/of_device.h>
>>  #include <linux/of_reserved_mem.h>
>>  #include <linux/platform_device.h>
>> +#include <linux/pm_runtime.h>
>>  #include <linux/dma-mapping.h>
>>  #include <linux/remoteproc.h>
>>  #include <linux/mailbox_client.h>
>> @@ -37,6 +38,9 @@
>>  #include "omap_remoteproc.h"
>>  #include "remoteproc_internal.h"
>>  
>> +/* default auto-suspend delay (ms) */
>> +#define DEFAULT_AUTOSUSPEND_DELAY		10000
>> +
>>  /**
>>   * struct omap_rproc_boot_data - boot data structure for the DSP omap rprocs
>>   * @syscon: regmap handle for the system control configuration module
>> @@ -83,6 +87,8 @@ struct omap_rproc_timer {
>>   * @num_mems: number of internal memory regions
>>   * @num_timers: number of rproc timer(s)
>>   * @timers: timer(s) info used by rproc
>> + * @autosuspend_delay: auto-suspend delay value to be used for runtime pm
>> + * @need_resume: if true a resume is needed in the system resume callback
>>   * @rproc: rproc handle
>>   * @reset: reset handle
>>   * @pm_comp: completion primitive to sync for suspend response
>> @@ -97,6 +103,8 @@ struct omap_rproc {
>>  	int num_mems;
>>  	int num_timers;
>>  	struct omap_rproc_timer *timers;
>> +	int autosuspend_delay;
>> +	bool need_resume;
>>  	struct rproc *rproc;
>>  	struct reset_control *reset;
>>  	struct completion pm_comp;
>> @@ -407,11 +415,23 @@ static void omap_rproc_kick(struct rproc *rproc, int vqid)
>>  	struct device *dev = rproc->dev.parent;
>>  	int ret;
>>  
>> +	/* wake up the rproc before kicking it */
>> +	ret = pm_runtime_get_sync(dev);
>> +	if (WARN_ON(ret < 0)) {
>> +		dev_err(dev, "pm_runtime_get_sync() failed during kick, ret = %d\n",
>> +			ret);
>> +		pm_runtime_put_noidle(dev);
>> +		return;
>> +	}
>> +
>>  	/* send the index of the triggered virtqueue in the mailbox payload */
>>  	ret = mbox_send_message(oproc->mbox, (void *)vqid);
>>  	if (ret < 0)
>>  		dev_err(dev, "failed to send mailbox message, status = %d\n",
>>  			ret);
>> +
>> +	pm_runtime_mark_last_busy(dev);
>> +	pm_runtime_put_autosuspend(dev);
>>  }
>>  
>>  /**
>> @@ -504,6 +524,18 @@ static int omap_rproc_start(struct rproc *rproc)
>>  		goto disable_timers;
>>  	}
>>  
>> +	/*
>> +	 * remote processor is up, so update the runtime pm status and
>> +	 * enable the auto-suspend. The device usage count is incremented
>> +	 * manually for balancing it for auto-suspend
>> +	 */
>> +	pm_runtime_set_active(dev);
>> +	pm_runtime_use_autosuspend(dev);
>> +	pm_runtime_get_noresume(dev);
>> +	pm_runtime_enable(dev);
>> +	pm_runtime_mark_last_busy(dev);
>> +	pm_runtime_put_autosuspend(dev);
>> +
>>  	return 0;
>>  
>>  disable_timers:
>> @@ -516,20 +548,52 @@ static int omap_rproc_start(struct rproc *rproc)
>>  /* power off the remote processor */
>>  static int omap_rproc_stop(struct rproc *rproc)
>>  {
>> +	struct device *dev = rproc->dev.parent;
>>  	struct omap_rproc *oproc = rproc->priv;
>>  	int ret;
>>  
>> +	/*
>> +	 * cancel any possible scheduled runtime suspend by incrementing
>> +	 * the device usage count, and resuming the device. The remoteproc
>> +	 * also needs to be woken up if suspended, to avoid the remoteproc
>> +	 * OS to continue to remember any context that it has saved, and
>> +	 * avoid potential issues in misindentifying a subsequent device
>> +	 * reboot as a power restore boot
>> +	 */
>> +	ret = pm_runtime_get_sync(dev);
>> +	if (ret < 0) {
>> +		pm_runtime_put_noidle(dev);
>> +		return ret;
>> +	}
>> +
>>  	ret = reset_control_assert(oproc->reset);
>>  	if (ret)
>> -		return ret;
>> +		goto out;
>>  
>>  	ret = omap_rproc_disable_timers(rproc, true);
>>  	if (ret)
>> -		return ret;
>> +		goto enable_device;
>>  
>>  	mbox_free_channel(oproc->mbox);
>>  
>> +	/*
>> +	 * update the runtime pm states and status now that the remoteproc
>> +	 * has stopped
>> +	 */
>> +	pm_runtime_disable(dev);
>> +	pm_runtime_dont_use_autosuspend(dev);
>> +	pm_runtime_put_noidle(dev);
>> +	pm_runtime_set_suspended(dev);
>> +
>>  	return 0;
>> +
>> +enable_device:
>> +	reset_control_deassert(oproc->reset);
>> +out:
>> +	/* schedule the next auto-suspend */
>> +	pm_runtime_mark_last_busy(dev);
>> +	pm_runtime_put_autosuspend(dev);
>> +	return ret;
>>  }
>>  
>>  /**
>> @@ -586,17 +650,19 @@ static bool _is_rproc_in_standby(struct omap_rproc *oproc)
>>  
>>  /* 1 sec is long enough time to let the remoteproc side suspend the device */
>>  #define DEF_SUSPEND_TIMEOUT 1000
>> -static int _omap_rproc_suspend(struct rproc *rproc)
>> +static int _omap_rproc_suspend(struct rproc *rproc, bool auto_suspend)
>>  {
>>  	struct device *dev = rproc->dev.parent;
>>  	struct omap_rproc *oproc = rproc->priv;
>>  	unsigned long to = msecs_to_jiffies(DEF_SUSPEND_TIMEOUT);
>>  	unsigned long ta = jiffies + to;
>> +	u32 suspend_msg = auto_suspend ?
>> +				RP_MBOX_SUSPEND_AUTO : RP_MBOX_SUSPEND_SYSTEM;
>>  	int ret;
>>  
>>  	reinit_completion(&oproc->pm_comp);
>>  	oproc->suspend_acked = false;
>> -	ret = mbox_send_message(oproc->mbox, (void *)RP_MBOX_SUSPEND_SYSTEM);
>> +	ret = mbox_send_message(oproc->mbox, (void *)suspend_msg);
>>  	if (ret < 0) {
>>  		dev_err(dev, "PM mbox_send_message failed: %d\n", ret);
>>  		return ret;
>> @@ -640,32 +706,62 @@ static int _omap_rproc_suspend(struct rproc *rproc)
>>  		goto enable_device;
>>  	}
>>  
>> +	/*
>> +	 * IOMMUs would have to be disabled specifically for runtime suspend.
>> +	 * They are handled automatically through System PM callbacks for
>> +	 * regular system suspend
>> +	 */
>> +	if (auto_suspend) {
>> +		ret = omap_iommu_domain_deactivate(rproc->domain);
>> +		if (ret) {
>> +			dev_err(dev, "iommu domain deactivate failed %d\n",
>> +				ret);
>> +			goto enable_timers;
>> +		}
>> +	}
>> +
>>  	return 0;
>>  
>> +enable_timers:
>> +	/* ignore errors on re-enabling code */
>> +	omap_rproc_enable_timers(rproc, false);
>>  enable_device:
>>  	reset_control_deassert(oproc->reset);
>>  	return ret;
>>  }
>>  
>> -static int _omap_rproc_resume(struct rproc *rproc)
>> +static int _omap_rproc_resume(struct rproc *rproc, bool auto_suspend)
>>  {
>>  	struct device *dev = rproc->dev.parent;
>>  	struct omap_rproc *oproc = rproc->priv;
>>  	int ret;
>>  
>> +	/*
>> +	 * IOMMUs would have to be enabled specifically for runtime resume.
>> +	 * They would have been already enabled automatically through System
>> +	 * PM callbacks for regular system resume
>> +	 */
>> +	if (auto_suspend) {
>> +		ret = omap_iommu_domain_activate(rproc->domain);
>> +		if (ret) {
>> +			dev_err(dev, "omap_iommu activate failed %d\n", ret);
>> +			goto out;
>> +		}
>> +	}
>> +
>>  	/* boot address could be lost after suspend, so restore it */
>>  	if (oproc->boot_data) {
>>  		ret = omap_rproc_write_dsp_boot_addr(rproc);
>>  		if (ret) {
>>  			dev_err(dev, "boot address restore failed %d\n", ret);
>> -			goto out;
>> +			goto suspend_iommu;
>>  		}
>>  	}
>>  
>>  	ret = omap_rproc_enable_timers(rproc, false);
>>  	if (ret) {
>>  		dev_err(dev, "enabling timers during resume failed %d\n", ret);
>> -		goto out;
>> +		goto suspend_iommu;
>>  	}
>>  
>>  	ret = reset_control_deassert(oproc->reset);
>> @@ -678,6 +774,9 @@ static int _omap_rproc_resume(struct rproc *rproc)
>>  
>>  disable_timers:
>>  	omap_rproc_disable_timers(rproc, false);
>> +suspend_iommu:
>> +	if (auto_suspend)
>> +		omap_iommu_domain_deactivate(rproc->domain);
>>  out:
>>  	return ret;
>>  }
>> @@ -686,6 +785,7 @@ static int __maybe_unused omap_rproc_suspend(struct device *dev)
>>  {
>>  	struct platform_device *pdev = to_platform_device(dev);
>>  	struct rproc *rproc = platform_get_drvdata(pdev);
>> +	struct omap_rproc *oproc = rproc->priv;
>>  	int ret = 0;
>>  
>>  	mutex_lock(&rproc->lock);
>> @@ -700,13 +800,19 @@ static int __maybe_unused omap_rproc_suspend(struct device *dev)
>>  		goto out;
>>  	}
>>  
>> -	ret = _omap_rproc_suspend(rproc);
>> +	ret = _omap_rproc_suspend(rproc, false);
>>  	if (ret) {
>>  		dev_err(dev, "suspend failed %d\n", ret);
>>  		goto out;
>>  	}
>>  
>> +	/*
>> +	 * remoteproc is running at the time of system suspend, so remember
>> +	 * it so as to wake it up during system resume
>> +	 */
>> +	oproc->need_resume = true;
>>  	rproc->state = RPROC_SUSPENDED;
>> +
>>  out:
>>  	mutex_unlock(&rproc->lock);
>>  	return ret;
>> @@ -716,6 +822,7 @@ static int __maybe_unused omap_rproc_resume(struct device *dev)
>>  {
>>  	struct platform_device *pdev = to_platform_device(dev);
>>  	struct rproc *rproc = platform_get_drvdata(pdev);
>> +	struct omap_rproc *oproc = rproc->priv;
>>  	int ret = 0;
>>  
>>  	mutex_lock(&rproc->lock);
>> @@ -727,17 +834,86 @@ static int __maybe_unused omap_rproc_resume(struct device *dev)
>>  		goto out;
>>  	}
>>  
>> -	ret = _omap_rproc_resume(rproc);
>> +	/*
>> +	 * remoteproc was auto-suspended at the time of system suspend,
>> +	 * so no need to wake-up the processor (leave it in suspended
>> +	 * state, will be woken up during a subsequent runtime_resume)
>> +	 */
>> +	if (!oproc->need_resume)
>> +		goto out;
>> +
>> +	ret = _omap_rproc_resume(rproc, false);
>>  	if (ret) {
>>  		dev_err(dev, "resume failed %d\n", ret);
>>  		goto out;
>>  	}
>>  
>> +	oproc->need_resume = false;
>>  	rproc->state = RPROC_RUNNING;
>> +
>> +	pm_runtime_mark_last_busy(dev);
>>  out:
>>  	mutex_unlock(&rproc->lock);
>>  	return ret;
>>  }
>> +
>> +static int omap_rproc_runtime_suspend(struct device *dev)
>> +{
>> +	struct rproc *rproc = dev_get_drvdata(dev);
>> +	struct omap_rproc *oproc = rproc->priv;
>> +	int ret;
>> +
> 
> Shouldn't the rproc->lock be held here?  Same for omap_rproc_runtime_resume().

Yeah, we can add them like in the regular suspend/resume functions.

regards
Suman


> 
>> +	if (rproc->state == RPROC_CRASHED) {
>> +		dev_dbg(dev, "rproc cannot be runtime suspended when crashed!\n");
>> +		return -EBUSY;
>> +	}
>> +
>> +	if (WARN_ON(rproc->state != RPROC_RUNNING)) {
>> +		dev_err(dev, "rproc cannot be runtime suspended when not running!\n");
>> +		return -EBUSY;
>> +	}
>> +
>> +	/*
>> +	 * do not even attempt suspend if the remote processor is not
>> +	 * idled for runtime auto-suspend
>> +	 */
>> +	if (!_is_rproc_in_standby(oproc)) {
>> +		ret = -EBUSY;
>> +		goto abort;
>> +	}
>> +
>> +	ret = _omap_rproc_suspend(rproc, true);
>> +	if (ret)
>> +		goto abort;
>> +
>> +	rproc->state = RPROC_SUSPENDED;
>> +	return 0;
>> +
>> +abort:
>> +	pm_runtime_mark_last_busy(dev);
>> +	return ret;
>> +}
>> +
>> +static int omap_rproc_runtime_resume(struct device *dev)
>> +{
>> +	struct rproc *rproc = dev_get_drvdata(dev);
>> +	int ret;
>> +
>> +	if (WARN_ON(rproc->state != RPROC_SUSPENDED)) {
>> +		dev_err(dev, "rproc cannot be runtime resumed if not suspended! state=%d\n",
>> +			rproc->state);
>> +		return -EBUSY;
>> +	}
>> +
>> +	ret = _omap_rproc_resume(rproc, true);
>> +	if (ret) {
>> +		dev_err(dev, "runtime resume failed %d\n", ret);
>> +		return ret;
>> +	}
>> +
>> +	rproc->state = RPROC_RUNNING;
>> +	return 0;
>> +}
>>  #endif /* CONFIG_PM */
>>  
>>  static const struct omap_rproc_mem_data ipu_mems[] = {
>> @@ -983,6 +1159,12 @@ static int omap_rproc_probe(struct platform_device *pdev)
>>  	}
>>  
>>  	init_completion(&oproc->pm_comp);
>> +	oproc->autosuspend_delay = DEFAULT_AUTOSUSPEND_DELAY;
>> +
>> +	of_property_read_u32(pdev->dev.of_node, "ti,autosuspend-delay-ms",
>> +			     &oproc->autosuspend_delay);
>> +
>> +	pm_runtime_set_autosuspend_delay(&pdev->dev, oproc->autosuspend_delay);
>>  
>>  	oproc->fck = devm_clk_get(&pdev->dev, 0);
>>  	if (IS_ERR(oproc->fck)) {
>> @@ -1025,6 +1207,8 @@ static int omap_rproc_remove(struct platform_device *pdev)
>>  
>>  static const struct dev_pm_ops omap_rproc_pm_ops = {
>>  	SET_SYSTEM_SLEEP_PM_OPS(omap_rproc_suspend, omap_rproc_resume)
>> +	SET_RUNTIME_PM_OPS(omap_rproc_runtime_suspend,
>> +			   omap_rproc_runtime_resume, NULL)
>>  };
>>  
>>  static struct platform_driver omap_rproc_driver = {
>> -- 
>> 2.17.1
>>
>> --
>> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki

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