linux-kernel - Re: [PATCH V3 3/5] i3c: mipi-i3c-hci: Allow parent to manage runtime PM

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Message-ID: <aYS9WwwjgZi5UDTE@lizhi-Precision-Tower-5810>
Date: Thu, 5 Feb 2026 10:55:07 -0500
From: Frank Li <Frank.li@....com>
To: Adrian Hunter <adrian.hunter@...el.com>
Cc: alexandre.belloni@...tlin.com, rafael@...nel.org,
	linux-i3c@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org
Subject: Re: [PATCH V3 3/5] i3c: mipi-i3c-hci: Allow parent to manage runtime
 PM

On Thu, Feb 05, 2026 at 12:09:13PM +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 runtime PM callbacks are
> invoked in a controlled and synchronized manner.
>
> For example, if the parent enables IBI-wakeup when transitioning into a
> low-power state, 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 low-level runtime PM suspend and resume helpers so that
>     the parent can explicitly invoke them.
>
>   * Add a new quirk, HCI_QUIRK_RPM_PARENT_MANAGED, allowing platforms to
>     bypass per-instance runtime PM callbacks and delegate control to the
>     parent device.
>
>   * 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>
> ---
Reviewed-by: Frank Li <Frank.Li@....com>
>
>
> Changes in V3:
>
> 	None
>
> Changes in V2:
>
> 	For HCI_QUIRK_RPM_PARENT_MANAGED case, change from
> 	disabling runtime PM to instead causing the runtime PM
> 	callbacks to do nothing
>
>
>  drivers/i3c/master/mipi-i3c-hci/core.c | 28 ++++++++++++++++++++++----
>  drivers/i3c/master/mipi-i3c-hci/hci.h  |  6 ++++++
>  2 files changed, 30 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/i3c/master/mipi-i3c-hci/core.c b/drivers/i3c/master/mipi-i3c-hci/core.c
> index ec4dbe64c35e..149b3fad34b5 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_rpm_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_rpm_suspend);
>
> -static int i3c_hci_runtime_resume(struct device *dev)
> +int i3c_hci_rpm_resume(struct device *dev)
>  {
>  	struct i3c_hci *hci = dev_get_drvdata(dev);
>  	int ret;
> @@ -768,6 +769,27 @@ static int i3c_hci_runtime_resume(struct device *dev)
>
>  	return 0;
>  }
> +EXPORT_SYMBOL_GPL(i3c_hci_rpm_resume);
> +
> +static int i3c_hci_runtime_suspend(struct device *dev)
> +{
> +	struct i3c_hci *hci = dev_get_drvdata(dev);
> +
> +	if (hci->quirks & HCI_QUIRK_RPM_PARENT_MANAGED)
> +		return 0;
> +
> +	return i3c_hci_rpm_suspend(dev);
> +}
> +
> +static int i3c_hci_runtime_resume(struct device *dev)
> +{
> +	struct i3c_hci *hci = dev_get_drvdata(dev);
> +
> +	if (hci->quirks & HCI_QUIRK_RPM_PARENT_MANAGED)
> +		return 0;
> +
> +	return i3c_hci_rpm_resume(dev);
> +}
>
>  static int i3c_hci_suspend(struct device *dev)
>  {
> @@ -812,8 +834,6 @@ 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);
> diff --git a/drivers/i3c/master/mipi-i3c-hci/hci.h b/drivers/i3c/master/mipi-i3c-hci/hci.h
> index 819328a85b84..584ee632b634 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_rpm_suspend(struct device *dev);
> +int i3c_hci_rpm_resume(struct device *dev);
> +
>  #endif
> --
> 2.51.0
>