linux-kernel - Re: [PATCH 5/7] i3c: mipi-i3c-hci: Allow parent to manage runtime PM

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Message-ID: <aXvKZK8tTnCDGzth@lizhi-Precision-Tower-5810>
Date: Thu, 29 Jan 2026 16:00:20 -0500
From: Frank Li <Frank.li@....com>
To: Adrian Hunter <adrian.hunter@...el.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 Thu, Jan 29, 2026 at 10:28:14PM +0200, Adrian Hunter wrote:
> 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.

It align my assumption, why need complex solution.

SDA->PME->IRQ should handle by hardware, so irq handle queue IBI to working
queue.

IBI work will try do transfer, which will call runtime resume(), then
transfer data.

What's issue?

Frank

>
> >
> > 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
> >>
>