Date:   Thu, 19 Dec 2019 14:46:03 -0700
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     Tero Kristo <t-kristo@...com>
Cc:     bjorn.andersson@...aro.org, ohad@...ery.com,
        linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-omap@...r.kernel.org, Suman Anna <s-anna@...com>
Subject: Re: [PATCHv3 12/15] remoteproc/omap: add support for system
 suspend/resume

On Fri, Dec 13, 2019 at 02:55:34PM +0200, Tero Kristo wrote:
> From: Suman Anna <s-anna@...com>
> 
> This patch adds the support for system suspend/resume to the
> OMAP remoteproc driver so that the OMAP remoteproc devices can
> be suspended/resumed during a system suspend/resume. The support
> is added through the driver PM .suspend/.resume callbacks, and
> requires appropriate support from the OS running on the remote
> processors.
> 
> The IPU & DSP remote processors typically have their own private
> modules like registers, internal memories, caches etc. The context
> of these modules need to be saved and restored properly for a
> suspend/resume to work. These are in general not accessible from
> the MPU, so the remote processors themselves have to implement
> the logic for the context save & restore of these modules.
> 
> The OMAP remoteproc driver initiates a suspend by sending a mailbox
> message requesting the remote processor to save its context and
> enter into an idle/standby state. The remote processor should
> usually stop whatever processing it is doing to switch to a context
> save mode. The OMAP remoteproc driver detects the completion of
> the context save by checking the module standby status for the
> remoteproc device. It also stops any resources used by the remote
> processors like the timers. The timers need to be running only
> when the processor is active and executing, and need to be stopped
> otherwise to allow the timer driver to reach low-power states. The
> IOMMUs are automatically suspended by the PM core during the late
> suspend stage, after the remoteproc suspend process is completed by
> putting the remote processor cores into reset. Thereafter, the Linux
> kernel can put the domain into further lower power states as possible.
> 
> The resume sequence undoes the operations performed in the PM suspend
> callback, by starting the timers and finally releasing the processors
> from reset. This requires that the remote processor side OS be able to
> distinguish a power-resume boot from a power-on/cold boot, restore the
> context of its private modules saved during the suspend phase, and
> resume executing code from where it was suspended. The IOMMUs would
> have been resumed by the PM core during early resume, so they are
> already enabled by the time remoteproc resume callback gets invoked.
> 
> The remote processors should save their context into System RAM (DDR),
> as any internal memories are not guaranteed to retain context as it
> depends on the lowest power domain that the remote processor device
> is put into. The management of the DDR contents will be managed by
> the Linux kernel.
> 
> 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>
> ---
>  drivers/remoteproc/omap_remoteproc.c | 179 +++++++++++++++++++++++++++
>  drivers/remoteproc/omap_remoteproc.h |  18 ++-
>  2 files changed, 195 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/remoteproc/omap_remoteproc.c b/drivers/remoteproc/omap_remoteproc.c
> index 9c750c2ab29d..0a9b9f7d20da 100644
> --- a/drivers/remoteproc/omap_remoteproc.c
> +++ b/drivers/remoteproc/omap_remoteproc.c
> @@ -16,6 +16,7 @@
>  #include <linux/kernel.h>
>  #include <linux/module.h>
>  #include <linux/err.h>
> +#include <linux/io.h>
>  #include <linux/of_device.h>
>  #include <linux/of_reserved_mem.h>
>  #include <linux/platform_device.h>
> @@ -23,10 +24,13 @@
>  #include <linux/remoteproc.h>
>  #include <linux/mailbox_client.h>
>  #include <linux/omap-mailbox.h>
> +#include <linux/omap-iommu.h>

Please move this up by one line.

>  #include <linux/regmap.h>
>  #include <linux/mfd/syscon.h>
>  #include <linux/reset.h>
>  #include <clocksource/timer-ti-dm.h>
> +#include <linux/clk.h>
> +#include <linux/clk/ti.h>

Unless there is a dependency with timer-ti-dm.h, these should go just above linux/err.h

>  
>  #include <linux/platform_data/dmtimer-omap.h>
>  
> @@ -81,6 +85,9 @@ struct omap_rproc_timer {
>   * @timers: timer(s) info used by rproc
>   * @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
>   */
>  struct omap_rproc {
>  	struct mbox_chan *mbox;
> @@ -92,6 +99,9 @@ struct omap_rproc {
>  	struct omap_rproc_timer *timers;
>  	struct rproc *rproc;
>  	struct reset_control *reset;
> +	struct completion pm_comp;
> +	struct clk *fck;
> +	bool suspend_acked;
>  };
>  
>  /**
> @@ -349,6 +359,11 @@ static void omap_rproc_mbox_callback(struct mbox_client *client, void *data)
>  	case RP_MBOX_ECHO_REPLY:
>  		dev_info(dev, "received echo reply from %s\n", name);
>  		break;
> +	case RP_MBOX_SUSPEND_ACK:

We can't get away with implicit fallthroughs anymore - please add /* Fall through */"

> +	case RP_MBOX_SUSPEND_CANCEL:
> +		oproc->suspend_acked = msg == RP_MBOX_SUSPEND_ACK;
> +		complete(&oproc->pm_comp);
> +		break;
>  	default:
>  		if (msg >= RP_MBOX_READY && msg < RP_MBOX_END_MSG)
>  			return;
> @@ -529,6 +544,157 @@ static const struct rproc_ops omap_rproc_ops = {
>  	.da_to_va	= omap_rproc_da_to_va,
>  };
>  
> +#ifdef CONFIG_PM
> +static bool _is_rproc_in_standby(struct omap_rproc *oproc)
> +{
> +	return ti_clk_is_in_standby(oproc->fck);
> +}
> +
> +/* 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)
> +{
> +	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;
> +	int ret;
> +
> +	reinit_completion(&oproc->pm_comp);
> +	oproc->suspend_acked = false;
> +	ret = mbox_send_message(oproc->mbox, (void *)RP_MBOX_SUSPEND_SYSTEM);
> +	if (ret < 0) {
> +		dev_err(dev, "PM mbox_send_message failed: %d\n", ret);
> +		return ret;
> +	}
> +
> +	ret = wait_for_completion_timeout(&oproc->pm_comp, to);
> +	if (!oproc->suspend_acked)
> +		return -EBUSY;
> +
> +	/*
> +	 * The remoteproc side is returning the ACK message before saving the
> +	 * context, because the context saving is performed within a SYS/BIOS
> +	 * function, and it cannot have any inter-dependencies against the IPC
> +	 * layer. Also, as the SYS/BIOS needs to preserve properly the processor
> +	 * register set, sending this ACK or signalling the completion of the
> +	 * context save through a shared memory variable can never be the
> +	 * absolute last thing to be executed on the remoteproc side, and the
> +	 * MPU cannot use the ACK message as a sync point to put the remoteproc
> +	 * into reset. The only way to ensure that the remote processor has
> +	 * completed saving the context is to check that the module has reached
> +	 * STANDBY state (after saving the context, the SYS/BIOS executes the
> +	 * appropriate target-specific WFI instruction causing the module to
> +	 * enter STANDBY).
> +	 */
> +	while (!_is_rproc_in_standby(oproc)) {
> +		if (time_after(jiffies, ta))
> +			return -ETIME;
> +		schedule();
> +	}
> +
> +	reset_control_assert(oproc->reset);
> +
> +	ret = omap_rproc_disable_timers(rproc, false);
> +	if (ret) {
> +		dev_err(dev, "disabling timers during suspend failed %d\n",
> +			ret);
> +		goto enable_device;
> +	}
> +
> +	return 0;
> +
> +enable_device:
> +	reset_control_deassert(oproc->reset);
> +	return ret;
> +}
> +
> +static int _omap_rproc_resume(struct rproc *rproc)
> +{
> +	struct device *dev = rproc->dev.parent;
> +	struct omap_rproc *oproc = rproc->priv;
> +	int ret;
> +
> +	/* 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;
> +		}
> +	}
> +
> +	ret = omap_rproc_enable_timers(rproc, false);
> +	if (ret) {
> +		dev_err(dev, "enabling timers during resume failed %d\n",
> +			ret);

The "ret);" fits on the live above.

> +		goto out;
> +	}
> +
> +	reset_control_deassert(oproc->reset);
> +
> +out:
> +	return ret;
> +}
> +
> +static int __maybe_unused omap_rproc_suspend(struct device *dev)

The "__maybe_unused" can be dropped because this is within the #ifdef CONFIG_PM
block.

> +{
> +	struct platform_device *pdev = to_platform_device(dev);
> +	struct rproc *rproc = platform_get_drvdata(pdev);
> +	int ret = 0;
> +
> +	mutex_lock(&rproc->lock);
> +	if (rproc->state == RPROC_OFFLINE)
> +		goto out;
> +
> +	if (rproc->state == RPROC_SUSPENDED)
> +		goto out;
> +
> +	if (rproc->state != RPROC_RUNNING) {
> +		ret = -EBUSY;
> +		goto out;
> +	}
> +
> +	ret = _omap_rproc_suspend(rproc);
> +	if (ret) {
> +		dev_err(dev, "suspend failed %d\n", ret);
> +		goto out;
> +	}
> +
> +	rproc->state = RPROC_SUSPENDED;
> +out:
> +	mutex_unlock(&rproc->lock);
> +	return ret;
> +}
> +
> +static int __maybe_unused omap_rproc_resume(struct device *dev)

Same comment as above.

> +{
> +	struct platform_device *pdev = to_platform_device(dev);
> +	struct rproc *rproc = platform_get_drvdata(pdev);
> +	int ret = 0;
> +
> +	mutex_lock(&rproc->lock);
> +	if (rproc->state == RPROC_OFFLINE)
> +		goto out;
> +
> +	if (rproc->state != RPROC_SUSPENDED) {
> +		ret = -EBUSY;
> +		goto out;
> +	}
> +
> +	ret = _omap_rproc_resume(rproc);
> +	if (ret) {
> +		dev_err(dev, "resume failed %d\n", ret);
> +		goto out;
> +	}
> +
> +	rproc->state = RPROC_RUNNING;
> +out:
> +	mutex_unlock(&rproc->lock);
> +	return ret;
> +}
> +#endif /* CONFIG_PM */
> +
>  static const char * const ipu_mem_names[] = {
>  	"l2ram", NULL
>  };
> @@ -786,6 +952,14 @@ static int omap_rproc_probe(struct platform_device *pdev)
>  			oproc->num_timers);
>  	}
>  
> +	init_completion(&oproc->pm_comp);
> +
> +	oproc->fck = devm_clk_get(&pdev->dev, 0);
> +	if (IS_ERR(oproc->fck)) {
> +		ret = PTR_ERR(oproc->fck);
> +		goto free_rproc;
> +	}
> +

oproc->fck is not released if an error occurs in of_reserved_mem_device_init()
and rproc_add().

>  	ret = of_reserved_mem_device_init(&pdev->dev);
>  	if (ret) {
>  		dev_err(&pdev->dev, "device does not have specific CMA pool\n");
> @@ -818,11 +992,16 @@ static int omap_rproc_remove(struct platform_device *pdev)
>  	return 0;
>  }
>  
> +static const struct dev_pm_ops omap_rproc_pm_ops = {
> +	SET_SYSTEM_SLEEP_PM_OPS(omap_rproc_suspend, omap_rproc_resume)
> +};
> +
>  static struct platform_driver omap_rproc_driver = {
>  	.probe = omap_rproc_probe,
>  	.remove = omap_rproc_remove,
>  	.driver = {
>  		.name = "omap-rproc",
> +		.pm = &omap_rproc_pm_ops,
>  		.of_match_table = omap_rproc_of_match,
>  	},
>  };
> diff --git a/drivers/remoteproc/omap_remoteproc.h b/drivers/remoteproc/omap_remoteproc.h
> index 72f656c93caa..c73383e707c7 100644
> --- a/drivers/remoteproc/omap_remoteproc.h
> +++ b/drivers/remoteproc/omap_remoteproc.h
> @@ -1,7 +1,7 @@
>  /*
>   * Remote processor messaging
>   *
> - * Copyright (C) 2011 Texas Instruments, Inc.
> + * Copyright (C) 2011-2018 Texas Instruments, Inc.
>   * Copyright (C) 2011 Google, Inc.
>   * All rights reserved.
>   *
> @@ -57,6 +57,16 @@
>   * @RP_MBOX_ABORT_REQUEST: a "please crash" request, used for testing the
>   * recovery mechanism (to some extent).
>   *
> + * @RP_MBOX_SUSPEND_AUTO: auto suspend request for the remote processor
> + *
> + * @RP_MBOX_SUSPEND_SYSTEM: system suspend request for the remote processor
> + *
> + * @RP_MBOX_SUSPEND_ACK: successful response from remote processor for a
> + * suspend request
> + *
> + * @RP_MBOX_SUSPEND_CANCEL: a cancel suspend response from a remote processor
> + * on a suspend request
> + *
>   * Introduce new message definitions if any here.
>   *
>   * @RP_MBOX_END_MSG: Indicates end of known/defined messages from remote core
> @@ -70,7 +80,11 @@ enum omap_rp_mbox_messages {
>  	RP_MBOX_ECHO_REQUEST	= 0xFFFFFF03,
>  	RP_MBOX_ECHO_REPLY	= 0xFFFFFF04,
>  	RP_MBOX_ABORT_REQUEST	= 0xFFFFFF05,
> -	RP_MBOX_END_MSG		= 0xFFFFFF06,
> +	RP_MBOX_SUSPEND_AUTO	= 0xFFFFFF10,
> +	RP_MBOX_SUSPEND_SYSTEM	= 0xFFFFFF11,
> +	RP_MBOX_SUSPEND_ACK	= 0xFFFFFF12,
> +	RP_MBOX_SUSPEND_CANCEL	= 0xFFFFFF13,
> +	RP_MBOX_END_MSG		= 0xFFFFFF14,
>  };
>  
>  #endif /* _OMAP_RPMSG_H */
> -- 
> 2.17.1
> 
> --
> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki

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