On Wed, Jul 11, 2012 at 12:49 PM, Yinghai Lu <yinghai@xxxxxxxxxx> wrote: > On Wed, Jul 11, 2012 at 11:15 AM, Bjorn Helgaas <bhelgaas@xxxxxxxxxx> wrote: >> >> What's the connection with HP_SUPR_RM()? Is it just a coincidence >> that chipsets that set the "Hot-Plug Surprise" bit don't have this >> problem with the Presence Detect State bit? >> >> Using HP_SUPR_RM() seems like a totally bogus way to work around a >> presence detect issue. > > then we should blame the spec. What specifically are you referring to? I see this Presence Detect State text: Presence Detect State – This bit indicates the presence of an adapter in the slot, reflected by the logical “OR” of the Physical Layer in-band presence detect mechanism and, if present, any out-of-band presence detect mechanism defined for the slot’s corresponding form factor. Note that the in-band presence detect mechanism requires that power be applied to an adapter for its presence to be detected. Consequently, form factors that require a power controller for hot-plug must implement a physical pin presence detect mechanism. But I don't yet see the connection with the Hot-Plug Surprise bit. > and if you do the above changing, when plug the card into system, > kernel will bring that card online automatically without press > attention button. > that will be big change. I don't want to make a fundamental change in behavior like that. I'm just trying to understand why we should handle Presence Detect differently based on the Hot-Plug Surprise bit. The attention button is optional. What happens today when you plug a card into a slot with no attention button? -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
