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Message-ID: <dd681a97-de37-436b-b09e-5173c1de2f24@intel.com>
Date: Thu, 29 Jan 2026 22:28:14 +0200
From: Adrian Hunter <adrian.hunter@...el.com>
To: Frank Li <Frank.li@....com>
CC: <alexandre.belloni@...tlin.com>, <linux-i3c@...ts.infradead.org>,
<linux-kernel@...r.kernel.org>, <linux-pm@...r.kernel.org>
Subject: Re: [PATCH 5/7] i3c: mipi-i3c-hci: Allow parent to manage runtime PM
On 29/01/2026 22:00, Frank Li wrote:
> On Thu, Jan 29, 2026 at 08:18:39PM +0200, Adrian Hunter wrote:
>> Some platforms implement the MIPI I3C HCI Multi-Bus Instance capability,
>> where a single parent device hosts multiple I3C controller instances. In
>> such designs, the parent - not the individual child instances - may need to
>> coordinate runtime PM so that all controllers enter low-power states
>> together, and all runtime suspend callbacks are invoked in a controlled
>> and synchronized manner.
>>
>> For example, if the parent enables IBI-wakeup when transitioning into a
>> low-power state,
>
> Does your hardware support recieve IBI when runtime suspend?
When runtime suspended (in D3), the hardware first triggers a Power Management
Event (PME) when the SDA line is pulled low to signal the START condition of an IBI.
The PCI subsystem will then runtime-resume the device. When the bus is enabled,
the clock is started and the IBI is received.
>
> Frank
>
>> every bus instance must remain able to receive IBIs up
>> until that point. This requires deferring the individual controllers’
>> runtime suspend callbacks (which disable bus activity) until the parent
>> decides it is safe for all instances to suspend together.
>>
>> To support this usage model:
>>
>> * Export the controller's runtime PM suspend/resume callbacks so that
>> the parent can invoke them directly.
>>
>> * Add a new quirk, HCI_QUIRK_RPM_PARENT_MANAGED, which designates the
>> parent device as the controller’s runtime PM device (rpm_dev). When
>> used without HCI_QUIRK_RPM_ALLOWED, this also prevents the child
>> instance’s system-suspend callbacks from using
>> pm_runtime_force_suspend()/pm_runtime_force_resume(), since runtime
>> PM is managed entirely by the parent.
>>
>> * Move DEFAULT_AUTOSUSPEND_DELAY_MS into the header so it can be shared
>> by parent-managed PM implementations.
>>
>> The new quirk allows platforms with multi-bus parent-managed PM
>> infrastructure to correctly coordinate runtime PM across all I3C HCI
>> instances.
>>
>> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
>> ---
>> drivers/i3c/master/mipi-i3c-hci/core.c | 25 ++++++++++++++++---------
>> drivers/i3c/master/mipi-i3c-hci/hci.h | 6 ++++++
>> 2 files changed, 22 insertions(+), 9 deletions(-)
>>
>> diff --git a/drivers/i3c/master/mipi-i3c-hci/core.c b/drivers/i3c/master/mipi-i3c-hci/core.c
>> index ec4dbe64c35e..cb974b0f9e17 100644
>> --- a/drivers/i3c/master/mipi-i3c-hci/core.c
>> +++ b/drivers/i3c/master/mipi-i3c-hci/core.c
>> @@ -733,7 +733,7 @@ static int i3c_hci_reset_and_init(struct i3c_hci *hci)
>> return 0;
>> }
>>
>> -static int i3c_hci_runtime_suspend(struct device *dev)
>> +int i3c_hci_runtime_suspend(struct device *dev)
>> {
>> struct i3c_hci *hci = dev_get_drvdata(dev);
>> int ret;
>> @@ -746,8 +746,9 @@ static int i3c_hci_runtime_suspend(struct device *dev)
>>
>> return 0;
>> }
>> +EXPORT_SYMBOL_GPL(i3c_hci_runtime_suspend);
>>
>> -static int i3c_hci_runtime_resume(struct device *dev)
>> +int i3c_hci_runtime_resume(struct device *dev)
>> {
>> struct i3c_hci *hci = dev_get_drvdata(dev);
>> int ret;
>> @@ -768,6 +769,7 @@ static int i3c_hci_runtime_resume(struct device *dev)
>>
>> return 0;
>> }
>> +EXPORT_SYMBOL_GPL(i3c_hci_runtime_resume);
>>
>> static int i3c_hci_suspend(struct device *dev)
>> {
>> @@ -784,12 +786,14 @@ static int i3c_hci_resume_common(struct device *dev, bool rstdaa)
>> struct i3c_hci *hci = dev_get_drvdata(dev);
>> int ret;
>>
>> - if (!(hci->quirks & HCI_QUIRK_RPM_ALLOWED))
>> - return 0;
>> + if (!(hci->quirks & HCI_QUIRK_RPM_PARENT_MANAGED)) {
>> + if (!(hci->quirks & HCI_QUIRK_RPM_ALLOWED))
>> + return 0;
>>
>> - ret = pm_runtime_force_resume(dev);
>> - if (ret)
>> - return ret;
>> + ret = pm_runtime_force_resume(dev);
>> + if (ret)
>> + return ret;
>> + }
>>
>> ret = i3c_master_do_daa_ext(&hci->master, rstdaa);
>> if (ret)
>> @@ -812,8 +816,6 @@ static int i3c_hci_restore(struct device *dev)
>> return i3c_hci_resume_common(dev, true);
>> }
>>
>> -#define DEFAULT_AUTOSUSPEND_DELAY_MS 1000
>> -
>> static void i3c_hci_rpm_enable(struct device *dev)
>> {
>> struct i3c_hci *hci = dev_get_drvdata(dev);
>> @@ -962,6 +964,11 @@ static int i3c_hci_probe(struct platform_device *pdev)
>> if (hci->quirks & HCI_QUIRK_RPM_IBI_ALLOWED)
>> hci->master.rpm_ibi_allowed = true;
>>
>> + if (hci->quirks & HCI_QUIRK_RPM_PARENT_MANAGED) {
>> + hci->master.rpm_dev = pdev->dev.parent;
>> + hci->master.rpm_allowed = true;
>> + }
>> +
>> return i3c_master_register(&hci->master, &pdev->dev, &i3c_hci_ops, false);
>> }
>>
>> diff --git a/drivers/i3c/master/mipi-i3c-hci/hci.h b/drivers/i3c/master/mipi-i3c-hci/hci.h
>> index 819328a85b84..d0e7ad58ac15 100644
>> --- a/drivers/i3c/master/mipi-i3c-hci/hci.h
>> +++ b/drivers/i3c/master/mipi-i3c-hci/hci.h
>> @@ -147,6 +147,7 @@ struct i3c_hci_dev_data {
>> #define HCI_QUIRK_RESP_BUF_THLD BIT(4) /* Set resp buf thld to 0 for AMD platforms */
>> #define HCI_QUIRK_RPM_ALLOWED BIT(5) /* Runtime PM allowed */
>> #define HCI_QUIRK_RPM_IBI_ALLOWED BIT(6) /* IBI and Hot-Join allowed while runtime suspended */
>> +#define HCI_QUIRK_RPM_PARENT_MANAGED BIT(7) /* Runtime PM managed by parent device */
>>
>> /* global functions */
>> void mipi_i3c_hci_resume(struct i3c_hci *hci);
>> @@ -156,4 +157,9 @@ void amd_set_od_pp_timing(struct i3c_hci *hci);
>> void amd_set_resp_buf_thld(struct i3c_hci *hci);
>> void i3c_hci_sync_irq_inactive(struct i3c_hci *hci);
>>
>> +#define DEFAULT_AUTOSUSPEND_DELAY_MS 1000
>> +
>> +int i3c_hci_runtime_suspend(struct device *dev);
>> +int i3c_hci_runtime_resume(struct device *dev);
>> +
>> #endif
>> --
>> 2.51.0
>>
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