On Thu, Jan 04, 2024 at 02:34:52PM +0100, Rafael J. Wysocki wrote:
> On Thu, Jan 4, 2024 at 3:48 AM Kai-Heng Feng
> <kai.heng.feng@xxxxxxxxxxxxx> wrote:
> >
> > The function of acpi_power_meter module on Dell system requires IPMI
> > handler is installed and SMI is selected.
>
> Does the firmware use _DEP to let the OS know about this dependency?
>
> > So add a helper to let acpi_power_meter know when IPMI handler and SMI
> > are ready.
> >
> > Signed-off-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx>
> > ---
> > v3:
> > - New patch.
> >
> > drivers/acpi/acpi_ipmi.c | 17 ++++++++++++++++-
> > include/acpi/acpi_bus.h | 5 +++++
> > 2 files changed, 21 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/acpi/acpi_ipmi.c b/drivers/acpi/acpi_ipmi.c
> > index 0555f68c2dfd..54862cab7171 100644
> > --- a/drivers/acpi/acpi_ipmi.c
> > +++ b/drivers/acpi/acpi_ipmi.c
> > @@ -23,6 +23,8 @@ MODULE_LICENSE("GPL");
> > #define IPMI_TIMEOUT (5000)
> > #define ACPI_IPMI_MAX_MSG_LENGTH 64
> >
> > +static struct completion smi_selected;
> > +
> > struct acpi_ipmi_device {
> > /* the device list attached to driver_data.ipmi_devices */
> > struct list_head head;
> > @@ -463,8 +465,10 @@ static void ipmi_register_bmc(int iface, struct device *dev)
> > if (temp->handle == handle)
> > goto err_lock;
> > }
> > - if (!driver_data.selected_smi)
> > + if (!driver_data.selected_smi) {
> > driver_data.selected_smi = ipmi_device;
> > + complete(&smi_selected);
> > + }
> > list_add_tail(&ipmi_device->head, &driver_data.ipmi_devices);
> > mutex_unlock(&driver_data.ipmi_lock);
> >
> > @@ -578,10 +582,21 @@ acpi_ipmi_space_handler(u32 function, acpi_physical_address address,
> > return status;
> > }
> >
> > +int acpi_wait_for_acpi_ipmi(void)
> > +{
> > + long ret;
> > +
> > + ret = wait_for_completion_interruptible_timeout(&smi_selected, 2 * HZ);
> > +
> > + return ret > 0 ? 0 : -ETIMEDOUT;
>
> What will happen if the IPMI driver is unloaded after this has returned 0?
The IPMI driver can't be unloaded if it has a user.
I've been following this, but I know little about ACPI. Beyond this
solution, the only other solution I could come up with was to start the
IPMI driver earlier. But then you are in a chicken-and-egg situation
(https://dictionary.cambridge.org/dictionary/english/chicken-and-egg-situation).
Which was the reason for the SPMI table, but that's really kind of
useless for this, even if the SPMI table existed.
-corey
>
> > +}
> > +EXPORT_SYMBOL_GPL(acpi_wait_for_acpi_ipmi);
> > +
> > static int __init acpi_ipmi_init(void)
> > {
> > int result;
> > acpi_status status;
> > + init_completion(&smi_selected);
> >
> > if (acpi_disabled)
> > return 0;
> > diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
> > index 1216d72c650f..afa6e4d4bf46 100644
> > --- a/include/acpi/acpi_bus.h
> > +++ b/include/acpi/acpi_bus.h
> > @@ -821,11 +821,16 @@ static inline void acpi_put_acpi_dev(struct acpi_device *adev)
> > {
> > acpi_dev_put(adev);
> > }
> > +
> > +int acpi_wait_for_acpi_ipmi(void);
> > +
> > #else /* CONFIG_ACPI */
> >
> > static inline int register_acpi_bus_type(void *bus) { return 0; }
> > static inline int unregister_acpi_bus_type(void *bus) { return 0; }
> >
> > +static inline int acpi_wait_for_acpi_ipmi(void) { return 0; }
> > +
> > #endif /* CONFIG_ACPI */
> >
> > #endif /*__ACPI_BUS_H__*/
> > --
>
