Hi,
On Mon, Oct 06, 2025 at 11:32:38AM -0700, Brian Norris wrote:
Hi Mika,
On Mon, Oct 06, 2025 at 03:52:22PM +0200, Mika Westerberg wrote:
On Fri, Oct 03, 2025 at 03:40:09PM -0700, Brian Norris wrote:
From: Brian Norris briannorris@google.com
When transitioning to D3cold, __pci_set_power_state() will first transition a device to D3hot. If the device was already in D3hot, this will add excess work: (a) read/modify/write PMCSR; and (b) excess delay (pci_dev_d3_sleep()).
How come the device is already in D3hot when __pci_set_power_state() is called? IIRC PCI core will transition the device to low power state so that it passes there the deepest possible state, and at that point the device is still in D0. Then __pci_set_power_state() puts it into D3hot and then turns if the power resource -> D3cold.
What I'm missing here?
Some PCI drivers call pci_set_power_state(..., PCI_D3hot) on their own when preparing for runtime or system suspend, so by the time they hit pci_finish_runtime_suspend(), they're in D3hot. Then, pci_target_state() may still pick a lower state (D3cold).
Ah, right. Thanks for clarification.
Yeah, I agree with Bjorn and Mani that those calls should go away (PCI core does that already). That makes driver writes life simpler wrt. PCI PM.