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.
