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Message-ID: <aXu8TiFpMiIVk5Iq@lizhi-Precision-Tower-5810>
Date: Thu, 29 Jan 2026 15:00:14 -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 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?
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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