On Tue, Jun 13, 2023 at 9:57 AM Zhiren Chen (陈志仁) <Zhiren.Chen@xxxxxxxxxxxx> wrote: > > On Fri, 2023-06-09 at 19:58 +0200, Rafael J. Wysocki wrote: > > > > On Fri, Jun 9, 2023 at 1:49 PM Bjorn Helgaas <helgaas@xxxxxxxxxx> > > wrote: > > > > > > [+cc Rafael, linux-pm] > > > > > > On Fri, Jun 09, 2023 at 10:30:38AM +0800, Zhiren Chen wrote: > > > > From: Zhiren Chen <Zhiren.Chen@xxxxxxxxxxxx> > > > > > > > > The platform_pci_choose_state function and other low-level > > platform > > > > interfaces used by PCI power management processing did not take > > into > > > > account non-ACPI-supported platforms. This shortcoming can result > > in > > > > limitations and issues. > > > > > > > > For example, in embedded systems like smartphones, a PCI device > > can be > > > > shared by multiple processors for different purposes. The PCI > > device and > > > > some of the processors are controlled by Linux, while the rest of > > the > > > > processors runs its own operating system. > > > > When Linux initiates system-level sleep, if it does not consider > > the > > > > working state of the shared PCI device and forcefully sets the > > PCI device > > > > state to D3, it will affect the functionality of other processors > > that > > > > are currently using the PCI device. > > > > > > > > To address this problem, an interface should be created for PCI > > devices > > > > that don't support ACPI to enable accurate reporting of the power > > state > > > > during the PCI PM handling process. > > > > > > > > Signed-off-by: Zhiren Chen <Zhiren.Chen@xxxxxxxxxxxx> > > > > Something like the pci_platform_pm_ops introduced here had been there > > for several years and the only users of it known to me were ACPI and > > Intel MID, which is why it was dropped. > > > > I would like to see the platform code using these new callbacks in > > the > > first place. > > > I think that more and more embedded products will use PCI devices to > achieve higher performance for data transfer, and these products may > not necessarily support ACPI. > > When developing the Mediatek T8xx modem chip driver, I found that there > was no good way for T8xx to skip D3 setting in certain PM scenarios. Well, is there any code that you are planning to add to the mainline Linux kernel that is going to use the proposed interface? If not, the interface itself will not be useful in the mainline Linux kernel.
