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Subject: Re: [PATCHv6 12/14] remoteproc/omap: add support for runtime
 auto-suspend/resume
To:     Tero Kristo <t-kristo@ti.com>, <bjorn.andersson@linaro.org>,
        <ohad@wizery.com>, <linux-remoteproc@vger.kernel.org>, <afd@ti.com>
CC:     <linux-kernel@vger.kernel.org>, <mathieu.poirier@linaro.org>,
        <linux-omap@vger.kernel.org>
References: <20200211152125.23819-1-t-kristo@ti.com>
 <20200211152125.23819-13-t-kristo@ti.com>
From:   Suman Anna <s-anna@ti.com>
Message-ID: <d1c9c28d-c35f-1011-4938-6f42977a090f@ti.com>
Date:   Mon, 17 Feb 2020 16:18:54 -0600
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Hi Tero,

On 2/11/20 9:21 AM, Tero Kristo wrote:
> From: Suman Anna <s-anna@ti.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' under DT or by

This is now ti,autosuspend-delay-ms.

> updating the 'autosuspend_delay_ms' field at runtime through the sysfs
> interface.
>     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@ti.com>
> [t-kristo@ti.com: converted to use ti-sysc instead of hwmod]
> Signed-off-by: Tero Kristo <t-kristo@ti.com>
> ---
>  drivers/remoteproc/omap_remoteproc.c | 189 +++++++++++++++++++++++++--
>  1 file changed, 178 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/remoteproc/omap_remoteproc.c b/drivers/remoteproc/omap_remoteproc.c
> index e8d3520493e1..490a242130f9 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
> @@ -83,11 +87,14 @@ 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
>   * @fck: functional clock for the remoteproc
>   * @suspend_acked: state machine flag to store the suspend request ack
> + * @in_reset: if remoteproc is in reset or not
>   */
>  struct omap_rproc {
>  	struct mbox_chan *mbox;
> @@ -97,11 +104,14 @@ 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;
>  	struct clk *fck;
>  	bool suspend_acked;
> +	bool in_reset;
>  };
>  
>  /**
> @@ -403,11 +413,23 @@ 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);
>  }
>  
>  /**
> @@ -498,6 +520,12 @@ static int omap_rproc_start(struct rproc *rproc)
>  		goto disable_timers;
>  	}
>  
> +	oproc->in_reset = false;
> +
> +	pm_runtime_get_sync(dev);

There are still some issues with this patch, namely the timers are not
shut down cleanly. I also prefer to keep the pm_runtime API usage
symmetric between start() and stop() and not use two different styles
(essentially follow the style from the downstream version). This should
help us in eliminating the in_reset variable

> +	pm_runtime_mark_last_busy(dev);
> +	pm_runtime_put_autosuspend(dev);
> +
>  	return 0;
>  
>  disable_timers:
> @@ -510,6 +538,7 @@ 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;
>  
> @@ -517,12 +546,20 @@ static int omap_rproc_stop(struct rproc *rproc)
>  	if (ret)
>  		return ret;
>  
> +	oproc->in_reset = true;
> +
>  	ret = omap_rproc_disable_timers(rproc, true);
>  	if (ret)
>  		return ret;
>  
>  	mbox_free_channel(oproc->mbox);
>  
> +	/*
> +	 * update the runtime pm states and status now that the remoteproc
> +	 * has stopped
> +	 */
> +	pm_runtime_put_noidle(dev);
> +
>  	return 0;
>  }
>  
> @@ -579,17 +616,19 @@ 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;
> @@ -622,6 +661,8 @@ static int _omap_rproc_suspend(struct rproc *rproc)
>  
>  	reset_control_assert(oproc->reset);
>  
> +	oproc->in_reset = true;
> +
>  	ret = omap_rproc_disable_timers(rproc, false);
>  	if (ret) {
>  		dev_err(dev, "disabling timers during suspend failed %d\n",
> @@ -629,42 +670,79 @@ 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);
> -	if (ret) {
> -		dev_err(dev, "reset deassert failed %d\n", ret);
> -		goto disable_timers;
> +	if (oproc->in_reset) {
> +		ret = reset_control_deassert(oproc->reset);
> +		if (ret) {
> +			dev_err(dev, "reset deassert failed %d\n", ret);
> +			goto disable_timers;
> +		}
> +
> +		oproc->in_reset = false;
>  	}
>  
>  	return 0;
>  
> +suspend_iommu:
> +	if (auto_suspend)
> +		omap_iommu_domain_deactivate(rproc->domain);
>  disable_timers:
>  	omap_rproc_disable_timers(rproc, false);
>  
> @@ -676,6 +754,7 @@ 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);
> @@ -690,13 +769,19 @@ 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;
> @@ -706,6 +791,7 @@ 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);
> @@ -717,17 +803,87 @@ 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;
> +
> +	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 &&
> +		    rproc->state != RPROC_OFFLINE)) {
> +		dev_err(dev, "rproc cannot be runtime resumed if not suspended! state=%d\n", rproc->state);
> +		return -EBUSY;
> +	}
> +
> +	ret = _omap_rproc_resume(rproc, rproc->state == RPROC_SUSPENDED);
> +	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[] = {
> @@ -973,6 +1129,14 @@ 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);
> +	pm_runtime_use_autosuspend(&pdev->dev);
> +	pm_runtime_enable(&pdev->dev);

These are not unwound if there were failures in the code paths below.
Also, this gives a false status in sysfs as "suspended" in the case
where firmware is missing from the FS, and the device is never started.

regards
Suman

>  
>  	oproc->fck = devm_clk_get(&pdev->dev, 0);
>  	if (IS_ERR(oproc->fck)) {
> @@ -1009,12 +1173,15 @@ static int omap_rproc_remove(struct platform_device *pdev)
>  	rproc_del(rproc);
>  	rproc_free(rproc);
>  	of_reserved_mem_device_release(&pdev->dev);
> +	pm_runtime_disable(&pdev->dev);
>  
>  	return 0;
>  }
>  
>  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 = {
>