Date:   Thu, 19 Dec 2019 21:11:08 -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>, <linux-kernel@...r.kernel.org>,
        <linux-omap@...r.kernel.org>
Subject: Re: [PATCHv3 12/15] remoteproc/omap: add support for system
 suspend/resume

Hi Mathieu, Tero,

On 12/19/19 3:46 PM, Mathieu Poirier wrote:
> 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

No depencencies, can be reordered.

> 
>>  
>>  #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.

These are suspend/resume callbacks, so are actually controlled by
CONFIG_PM_SLEEP which can be disabled independently from runtime
suspend, and hence the annotation.

> 
>> +{
>> +	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().

We are using a devres managed API, so why do we need to release it
specifically?

> 
>>  	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.

%s/2018/2019/

regards
Suman

>>   * 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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