On 3/12/21 3:14 PM, Bjorn Helgaas wrote:
On Fri, Mar 12, 2021 at 02:11:03PM -0800, Kuppuswamy, Sathyanarayanan wrote:
On 3/12/21 1:33 PM, Bjorn Helgaas wrote:
On Mon, Mar 08, 2021 at 10:34:10PM -0800, sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx wrote:
From: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
+bool is_dpc_reset_active(struct pci_dev *dev)
+{
+ struct pci_host_bridge *host = pci_find_host_bridge(dev->bus);
+ u16 status;
+
+ if (!dev->dpc_cap)
+ return false;
+
+ /*
+ * If DPC is owned by firmware and EDR is not supported, there is
+ * no race between hotplug and DPC recovery handler. So return
+ * false.
+ */
+ if (!host->native_dpc && !IS_ENABLED(CONFIG_PCIE_EDR))
+ return false;
+
+ if (atomic_read_acquire(&dev->dpc_reset_active))
+ return true;
+
+ pci_read_config_word(dev, dev->dpc_cap + PCI_EXP_DPC_STATUS, &status);
+
+ return !!(status & PCI_EXP_DPC_STATUS_TRIGGER);
I know it's somewhat common in drivers/pci/, but I'm not really a
big fan of "!!".
I can change it to use ternary operator.
(status & PCI_EXP_DPC_STATUS_TRIGGER) ? true : false;
Ternary isn't terrible, but what's wrong with:
if (status & PCI_EXP_DPC_STATUS_TRIGGER)
return true;
return false;
I am fine with above format.
which matches the style of the rest of the function.
Looking at this again, we return "true" if either dpc_reset_active or
PCI_EXP_DPC_STATUS_TRIGGER. I haven't worked this all out, but that
pattern feels racy. I guess the thought is that if
PCI_EXP_DPC_STATUS_TRIGGER is set, dpc_reset_link() will be invoked
soon and we don't want to interfere?
Yes, the reason for checking dpc_reset_active before
PCI_EXP_DPC_STATUS_TRIGGER is because, we want suppress DLLSC events
till link comes back or it times out.
137 atomic_inc_return_acquire(&pdev->dpc_reset_active);
138
139 pci_write_config_word(pdev, cap + PCI_EXP_DPC_STATUS,
140 PCI_EXP_DPC_STATUS_TRIGGER);
141
142 if (!pcie_wait_for_link(pdev, true)) {
143 pci_info(pdev, "Data Link Layer Link Active not set in 1000 msec\n");
144 status = PCI_ERS_RESULT_DISCONNECT;
145 }
146
147 atomic_dec_return_release(&pdev->dpc_reset_active);
--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer
