Re: [PATCHv4 11/14] remoteproc/omap: add support for system suspend/resume

Suman Anna
2020-01-08T21:42:27Z

On 1/8/20 1:57 PM, Suman Anna wrote:
> On 1/2/20 7:18 AM, Tero Kristo wrote:
>> From: Suman Anna <s-anna@ti.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@ti.com>
>> [t-kristo@ti.com: converted to use ti-sysc instead of hwmod]
>> Signed-off-by: Tero Kristo <t-kristo@ti.com>
>> ---
>> v4:
>> - include headers sorted by name
>
>> - using #ifdef CONFIG_PM_SLEEP for suspend/resume ops
>
> Yeah, guess you missed my response comment on this on v3. This is
> actually old-style, so original code in v3 is good on this one.
>
> regards
> Suman
>
>>
>> drivers/remoteproc/omap_remoteproc.c | 181 +++++++++++++++++++++++++++
>> drivers/remoteproc/omap_remoteproc.h | 18 ++-
>> 2 files changed, 197 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/remoteproc/omap_remoteproc.c b/drivers/remoteproc/omap_remoteproc.c
>> index fd4700861a14..2a333565a9c1 100644
>> --- a/drivers/remoteproc/omap_remoteproc.c
>> +++ b/drivers/remoteproc/omap_remoteproc.c
>> @@ -15,13 +15,17 @@
>>
>> #include <linux/kernel.h>
>> #include <linux/module.h>
>> +#include <linux/clk.h>
>> +#include <linux/clk/ti.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>
>> #include <linux/dma-mapping.h>
>> #include <linux/remoteproc.h>
>> #include <linux/mailbox_client.h>
>> +#include <linux/omap-iommu.h>
>> #include <linux/omap-mailbox.h>
>> #include <linux/regmap.h>
>> #include <linux/mfd/syscon.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;
>> };
>>
>> /**
>> @@ -366,6 +376,12 @@ 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:
>> + /* 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;
>> @@ -554,6 +570,158 @@ 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);
>> + goto out;
>> + }
>> +
>> + reset_control_deassert(oproc->reset);

So, I actually did not comment specifically on this on v3 hoping that my
comment on the lack of error checking in v3 Patch 2 would have been
taken care of here as well.

Please do compare the overall code against our current downstream
release code as well. I still see some deltas, I have to double-check
the behavior as well once with the auto-suspend patch. Probably will do
that on the next version.

regards
Suman

>> +
>> +out:
>> + return ret;
>> +}
>> +
>> +#ifdef CONFIG_PM_SLEEP
>> +static int omap_rproc_suspend(struct device *dev)
>> +{
>> + 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 omap_rproc_resume(struct device *dev)
>> +{
>> + 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_SLEEP */
>> +#endif /* CONFIG_PM */
>> +
>> static const struct omap_rproc_mem_data ipu_mems[] = {
>> { .name = "l2ram", .dev_addr = 0x20000000 },
>> { },
>> @@ -796,6 +964,14 @@ 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;
>> + }
>> +
>> ret = of_reserved_mem_device_init(&pdev->dev);
>> if (ret) {
>> dev_err(&pdev->dev, "device does not have specific CMA pool\n");
>> @@ -828,11 +1004,16 @@ 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..8af37e46aa73 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) 2011-2020 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 */
>>
>