Re: [PATCH 1/1] hw/i386/acpi-build: add OSHP method support for SHPC driver load

[Michael S. Tsirkin]

On Mon, Jun 24, 2024 at 01:34:08PM +0000, Gao,Shiyuan wrote:
> > > SHPC driver will be loaded fail in i440fx platform, the dmesg shows
> > > that OS cannot get control of SHPC hotplug and hotplug device to
> > > the PCI bridge will fail when we use SHPC Native type:
> > >
> > >   [3.336059] shpchp 0000:00:03.0: Requesting control of SHPC hotplug via 
> > >OSHP (\_SB_.PCI0.S28_)
> > >   [3.337408] shpchp 0000:00:03.0: Requesting control of SHPC hotplug via 
> > >OSHP (\_SB_.PCI0)
> > >   [3.338710] shpchp 0000:00:03.0: Cannot get control of SHPC hotplug
> > >
> > > Add OSHP method support for SHPC driver load, the hotplug device to the 
> > > PCI bridge will
> > > success when we use SHPC Native type.
> > >
> > >   [1.703975] shpchp 0000:00:03.0: Requesting control of SHPC hotplug via 
> > >OSHP (\_SB_.PCI0.S18_)
> > >   [1.704934] shpchp 0000:00:03.0: Requesting control of SHPC hotplug via 
> > >OSHP (\_SB_.PCI0)
> > >   [1.705855] shpchp 0000:00:03.0: Gained control of SHPC hotplug 
> > >(\_SB_.PCI0)
> > >   [1.707054] shpchp 0000:00:03.0: HPC vendor_id 1b36 device_id 1 ss_vid 0 
> > >ss_did 0
> > >
> > > According to the acpi_pcihp, the OSHP method don't need parameter and 
> > > return value now.
> > >
> > >   shpc_probe
> > >     --> acpi_get_hp_hw_control_from_firmware
> > >       --> acpi_run_oshp
> > >         --> status = acpi_evaluate_object(handle, METHOD_NAME_OSHP, NULL, 
> > >NULL);
> > >
> > > Signed-off-by: Shiyuan Gao <gaoshiyuan@baidu.com>
> > > ---
> > >  hw/i386/acpi-build.c | 14 ++++++++++++++
> > >  1 file changed, 14 insertions(+)
> > >
> > > diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> > > index f4e366f64f..79622e6939 100644
> > > --- a/hw/i386/acpi-build.c
> > > +++ b/hw/i386/acpi-build.c
> > > @@ -1412,6 +1412,18 @@ static void build_acpi0017(Aml *table)
> > >      aml_append(table, scope);
> > >  }
> > >
> > > +static Aml *build_oshp_method(void)
> > > +{
> > > +    Aml *method;
> > > +
> > > +    /*
> > > +     * Request control of SHPC hotplug via OSHP method,
> > > +     * no need parameter and return value in acpi_pcihp.
> > > +     */
> >
> > Quote spec and earliest version documenting this, please.
> 
> I cann't find document describe this, only find in the kernel code
> and describe it in the commit message.

Hrrm you really should read the spec not just go by the fact things
happen to work.  Look up PCI Firmware Specification

-- 
MST