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Date: Fri, 20 Nov 2020 11:33:37 -0800 From: "Kuppuswamy, Sathyanarayanan" <sathyanarayanan.kuppuswamy@...ux.intel.com> To: "Raj, Ashok" <ashok.raj@...el.com>, Lukas Wunner <lukas@...ner.de> Cc: linux-pci@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>, linux-kernel@...r.kernel.org Subject: Re: [PATCH 1/1] pci: pciehp: Handle MRL interrupts to enable slot for hotplug. Hi, On 11/19/20 2:08 PM, Raj, Ashok wrote: >> If an Attention Button is present, the current behavior is to bring up >> the hotplug slot as soon as presence or link is detected. We don't wait >> for a button press. This is intended as a convience feature to bring up >> slots as quickly as possible, but the behavior can be changed if the >> button press and 5 second delay is preferred. > No personal preference, I thought that is how the code in Linux was > earlier. > > Looks like we still don't subscribe to PDC if ATTN is present? So you don't > get an event until someone presses the button to process hotplug right? > > pciehp_hpc.c:pcie_enable_notification() > { > .... > > * Always enable link events: thus link-up and link-down shall > * always be treated as hotplug and unplug respectively. Enable > * presence detect only if Attention Button is not present. > */ > cmd = PCI_EXP_SLTCTL_DLLSCE; > if (ATTN_BUTTN(ctrl)) > cmd |= PCI_EXP_SLTCTL_ABPE; > else > cmd |= PCI_EXP_SLTCTL_PDCE; > .... > } > > > Looks like we still wait for button press to process. When you don't have a > power control yes the DLLSC would kick in and we would process them. but if > you have power control, you won't turn on until the button press? > Yes, as per current logic, if attention button is present, then we don't subscribe to PDC event changes. we wait for button pressĀ to turn on/off the slot. -- Sathyanarayanan Kuppuswamy Linux Kernel Developer
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