[PATCH AUTOSEL 6.17-5.4] usb: xhci: plat: Facilitate using autosuspend for xhci plat devices

[Sasha Levin <sashal@kernel.org>]

From: Krishna Kurapati <krishna.kurapati@oss.qualcomm.com>

[ Upstream commit 41cf11946b9076383a2222bbf1ef57d64d033f66 ]

Allow autosuspend to be used by xhci plat device. For Qualcomm SoCs,
when in host mode, it is intended that the controller goes to suspend
state to save power and wait for interrupts from connected peripheral
to wake it up. This is particularly used in cases where a HID or Audio
device is connected. In such scenarios, the usb controller can enter
auto suspend and resume action after getting interrupts from the
connected device.

Signed-off-by: Krishna Kurapati <krishna.kurapati@oss.qualcomm.com>
Link: https://lore.kernel.org/r/20250916120436.3617598-1-krishna.kurapati@oss.qualcomm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

LLM Generated explanations, may be completely bogus:

YES. Adding `pm_runtime_use_autosuspend(&pdev->dev);` in
`xhci_plat_probe()` (`drivers/usb/host/xhci-plat.c:185`) finally lets
platform xHCI hosts honour runtime PM autosuspend, so boards that set
`power/control=auto` (such as the Qualcomm configurations called out in
the commit message) can actually drop the controller into low-power idle
instead of burning power indefinitely. The rest of the driver already
implements full runtime suspend/resume support (`drivers/usb/host/xhci-
plat.c:500-573`) and wraps probe/remove paths with the usual runtime-PM
bookkeeping (`drivers/usb/host/xhci-plat.c:355-390`,
`drivers/usb/host/xhci-plat.c:463-548`), so this line simply flips on an
otherwise wired-up capability. Risk is very low: runtime PM remains opt-
in because `pm_runtime_forbid()` keeps the default “on” policy
(`drivers/usb/host/xhci-plat.c:358-362`), and other SoC-specific xHCI
drivers have long invoked the same helper (for example
`drivers/usb/host/xhci-mtk.c:573` and `drivers/usb/host/xhci-
tegra.c:1943`). No dependent changes are required and there are no
follow-up fixes, so this targeted fix for a real power-management
regression is a good candidate for stable backporting.

 drivers/usb/host/xhci-plat.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/usb/host/xhci-plat.c b/drivers/usb/host/xhci-plat.c
index 5eb51797de326..dd57ffedcaa2f 100644
--- a/drivers/usb/host/xhci-plat.c
+++ b/drivers/usb/host/xhci-plat.c
@@ -171,6 +171,7 @@ int xhci_plat_probe(struct platform_device *pdev, struct device *sysdev, const s
 		return ret;
 
 	pm_runtime_set_active(&pdev->dev);
+	pm_runtime_use_autosuspend(&pdev->dev);
 	pm_runtime_enable(&pdev->dev);
 	pm_runtime_get_noresume(&pdev->dev);
 
-- 
2.51.0