Re: [PATCH] firewire: ohci: suppress unexpected system reboot in AMD Ryzen machines and ASM108x/VT630x PCIe cards

[Takashi Sakamoto <o-takashi@sakamocchi.jp>]

Hi Mario,

On Fri, Dec 29, 2023 at 08:30:00PM -0600, Mario Limonciello wrote:
> On 12/28/2023 21:57, Takashi Sakamoto wrote:
> > @@ -3527,6 +3534,45 @@ static const struct fw_card_driver ohci_driver = {
> >   	.stop_iso		= ohci_stop_iso,
> >   };
> > +// On PCI Express Root Complex in any type of AMD Ryzen machine, VIA VT6306/6307/6308 with Asmedia
> > +// ASM1083/1085 brings an inconvenience that read accesses to 'Isochronous Cycle Timer' register
> > +// (at offset 0xf0 in PCI I/O space) often causes unexpected system reboot. The mechanism is not
> > +// clear, since the read access to the other registers is enough safe; e.g. 'Node ID' register,
> > +// while it is probable due to detection of any type of PCIe error.
> > +#if IS_ENABLED(CONFIG_X86)
> > +
> > +#define PCI_DEVICE_ID_ASMEDIA_ASM108X	0x1080
> > +
> > +static bool detect_vt630x_with_asm1083_on_amd_ryzen_machine(const struct pci_dev *pdev,
> > +							    struct fw_ohci *ohci)
> > +{
> > +	const struct pci_dev *pcie_to_pci_bridge;
> > +	const struct cpuinfo_x86 *cinfo = &cpu_data(0);
> > +
> > +	// Detect any type of AMD Ryzen machine.
> > +	if (cinfo->x86_vendor != X86_VENDOR_AMD || cinfo->x86 < 0x17)
> > +		return false;
> 
> Maybe it's better to use X86_FEATURE_ZEN?

Indeed. We can use it under the condition branch for CONFIG_X86, like:

+       // Detect any type of AMD Ryzen machine.
+       if (!static_cpu_has(X86_FEATURE_ZEN))
+               return false;


Thanks

Takashi Sakamoto