linux-kernel - Re: [PATCH V6 4/4] firmware: ti_sci: Introduce system suspend resume support

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Message-ID: <8c330bd9-5f4e-8cd0-ed02-c3a696d7473a@ti.com>
Date:   Thu, 3 Aug 2023 11:00:11 -0500
From:   Andrew Davis <afd@...com>
To:     Dhruva Gole <d-gole@...com>
CC:     Nishanth Menon <nm@...com>, Tero Kristo <kristo@...nel.org>,
        "Santosh Shilimkar" <ssantosh@...nel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <linux-pm@...r.kernel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Praneeth Bajjuri <praneeth@...com>,
        Tony Lindgren <tony@...mide.com>,
        Dave Gerlach <d-gerlach@...com>,
        Vibhore Vardhan <vibhore@...com>, Georgi Vlaev <g-vlaev@...com>
Subject: Re: [PATCH V6 4/4] firmware: ti_sci: Introduce system suspend resume
 support

On 8/3/23 10:55 AM, Dhruva Gole wrote:
> On Aug 03, 2023 at 10:26:32 -0500, Andrew Davis wrote:
>> On 8/3/23 1:42 AM, Dhruva Gole wrote:
>>> Introduce system suspend resume calls that will allow the ti_sci
>>> driver to support deep sleep low power mode when the user space issues a
>>> suspend to mem.
>>>
>>> Also, write a ti_sci_prepare_system_suspend call to be used in the driver
>>> suspend handler to allow the system to identify the low power mode being
>>> entered and if necessary, send TISCI_MSG_PREPARE_SLEEP with information
>>> about the mode is being entered and the address for allocated memory for
>>> storing the context during Deep Sleep.
>>>
>>> We're using "pm_suspend_target_state" to map the kernel's target suspend
>>> state to SysFW low power mode. Make sure this is available only when
>>> CONFIG_SUSPEND is enabled.
>>>
>>> Co-developed-by: Dave Gerlach <d-gerlach@...com>
>>> Signed-off-by: Dave Gerlach <d-gerlach@...com>
>>> Signed-off-by: Vibhore Vardhan <vibhore@...com>
>>> Signed-off-by: Georgi Vlaev <g-vlaev@...com>
>>> Signed-off-by: Dhruva Gole <d-gole@...com>
>>> ---
>>>    drivers/firmware/ti_sci.c | 63 +++++++++++++++++++++++++++++++++++++++
>>>    1 file changed, 63 insertions(+)
>>>
> [..snip..]
>>> +static int ti_sci_suspend(struct device *dev)
>>> +{
>>> +	struct ti_sci_info *info = dev_get_drvdata(dev);
>>> +	int ret;
>>> +
>>> +	ret = ti_sci_cmd_set_io_isolation(&info->handle, TISCI_MSG_VALUE_IO_ENABLE);
>>
>> After this the will the IOs be in isolation? Or does the firmware wait
>> until power down begins later?
> 
>  From what I understand,
> IOs will be in isolation immediately
> 

That is what I understand too, so then any device that may need to do some
external communication for its suspend will not function, this must be the
last driver _suspend() the system calls, how do you enforce that?

Andrew

>>
>> Andrew
>>
>>> +	if (ret)
>>> +		return ret;
>>> +	dev_dbg(dev, "%s: set I/O isolation: %d\n", __func__, ret);
>>> +
>>> +	ret = ti_sci_prepare_system_suspend(info);
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static int ti_sci_resume(struct device *dev)
>>> +{
>>> +	struct ti_sci_info *info = dev_get_drvdata(dev);
>>> +	int ret;
>>> +
>>> +	ret = ti_sci_cmd_set_io_isolation(&info->handle, TISCI_MSG_VALUE_IO_DISABLE);
>>> +	if (ret)
>>> +		return ret;
>>> +	dev_dbg(dev, "%s: disable I/O isolation: %d\n", __func__, ret);
>>> +
>>> +	return 0;
>>> +}
>>> +
>>> +static DEFINE_SIMPLE_DEV_PM_OPS(ti_sci_pm_ops, ti_sci_suspend, ti_sci_resume);
>>> +
>>>    static int ti_sci_init_suspend(struct platform_device *pdev,
>>>    			       struct ti_sci_info *info)
>>>    {
>>> @@ -3759,6 +3821,7 @@ static struct platform_driver ti_sci_driver = {
>>>    	.driver = {
>>>    		   .name = "ti-sci",
>>>    		   .of_match_table = of_match_ptr(ti_sci_of_match),
>>> +		   .pm = &ti_sci_pm_ops,
>>>    	},
>>>    };
>>>    module_platform_driver(ti_sci_driver);
>