On Thu, Oct 26, 2023 at 12:47:31PM +0200, Anders Roxell wrote:
> On 2023-10-25 13:06, Bjorn Helgaas wrote:
> > On Wed, Oct 25, 2023 at 10:41:46AM -0700, D Scott Phillips wrote:
> > > Bjorn Helgaas <helgaas@xxxxxxxxxx> writes:
> > >
> > > > On Fri, Sep 29, 2023 at 05:20:36PM -0700, D Scott Phillips wrote:
> > > >> On Ampere Altra, PCIe hotplug is handled through ACPI. A side interface is
> > > >> also present to request system firmware control of attention LEDs. Add an
> > > >> ACPI PCI Hotplug companion driver to support attention LED control.
> > > >> ...
> > > >
> > > >> + arm_smccc_smc(REQUEST, LED_CMD, led_status(status), LED_ATTENTION,
> > > >> + pci_domain_nr(bus) | (PCI_SLOT(root_port->devfn) << 4), 0, 0,
> > > >
> > > > pci_domain_nr() returns "int" (normally 32 bits), but since this is an
> > > > ACPI system, the domain comes from _SEG, which is defined to be 16
> > > > bits (ACPI r6.5, sec 6.5.6).
> > > >
> > > > So it looks like ORing in the "slot << 4" clobbers the upper 12 bits
> > > > of _SEG.
> > > >
> > > > Is this code doing the right thing?
> > >
> > > Hi Bjorn,
> > >
> > > on these Altra platforms _SEG is limited within 0-11. I can add an `&
> > > 0xf` to pci_domain_nr() to make it clear that the segment number is
> > > encoded down into 4 bits in the smc request.
> >
> > If the following looks OK, we're all set. I put these on pci/hotplug
> > for v6.7, thanks!
> >
> > +static int set_attention_status(struct hotplug_slot *slot, u8 status)
> > +{
> > + struct arm_smccc_res res;
> > + struct pci_bus *bus;
> > + struct pci_dev *root_port;
> > + unsigned long flags;
> > + u32 handle;
> > + int ret = 0;
> > +
> > + bus = slot->pci_slot->bus;
> > + root_port = pcie_find_root_port(bus->self);
> > + if (!root_port)
> > + return -ENODEV;
> > +
> > + local_irq_save(flags);
> > + arm_smccc_smc(HANDLE_OPEN, led_service_id[0], led_service_id[1],
> > + led_service_id[2], led_service_id[3], 0, 0, 0, &res);
> > + if (res.a0) {
> > + ret = -ENODEV;
> > + goto out;
> > + }
> > + handle = res.a1 & 0xffff0000;
> > +
> > + arm_smccc_smc(REQUEST, LED_CMD, led_status(status), LED_ATTENTION,
> > + PCI_SLOT(root_port->devfn) << 4 | pci_domain_nr(bus) & 0xf,
> > + 0, 0, handle, &res);
> > + if (res.a0)
> > + ret = -ENODEV;
> > +
> > + arm_smccc_smc(HANDLE_CLOSE, handle, 0, 0, 0, 0, 0, 0, &res);
> > +
> > + out:
> > + local_irq_restore(flags);
> > + return ret;
> > +}
>
> Hi,
>
> Building todays linux-next tag next-20231026 for arm64 with
> CONFIG_HOTPLUG_PCI_ACPI_AMPERE_ALTRA=m I see the following build error.
>
> drivers/pci/hotplug/acpiphp_ampere_altra.c: In function 'set_attention_status':
> drivers/pci/hotplug/acpiphp_ampere_altra.c:63:75: error: suggest parentheses around arithmetic in operand of '|' [-Werror=parentheses]
> 63 | PCI_SLOT(root_port->devfn) << 4 | pci_domain_nr(bus) & 0xf,
> | ~~~~~~~~~~~~~~~~~~~^~~~~
> include/linux/arm-smccc.h:382:44: note: in definition of macro 'arm_smccc_smc'
> 382 | #define arm_smccc_smc(...) __arm_smccc_smc(__VA_ARGS__, NULL)
> | ^~~~~~~~~~~
> cc1: all warnings being treated as errors
> make[6]: *** [scripts/Makefile.build:243: drivers/pci/hotplug/acpiphp_ampere_altra.o] Error 1
My fault, fixed.
Bjorn
