Messages in this thread | | | Subject | Re: [PATCH v8 2/6] PCI/DPC: define a function to check and wait till port finish DPC handling | From | "Kuppuswamy, Sathyanarayanan" <> | Date | Wed, 7 Oct 2020 10:28:50 -0700 |
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On 10/7/20 4:31 AM, Ethan Zhao wrote: > Once root port DPC capability is enabled and triggered, at the beginning > of DPC is triggered, the DPC status bits are set by hardware and then > sends DPC/DLLSC/PDC interrupts to OS DPC and pciehp drivers, it will > take the port and software DPC interrupt handler 10ms to 50ms (test data > on ICS(Ice Lake SP platform, see > https://en.wikichip.org/wiki/intel/microarchitectures/ice_lake_(server) > & stable 5.9-rc6) to complete the DPC containment procedure This data is based on one particular architecture. So using this to create a timed loop in pci_wait_port_outdpc() looks incorrect.
I still recommend looking for some locking model to fix this issue (may be atomic state flag or lock). > till the DPC status is cleared at the end of the DPC interrupt handler. > > We use this function to check if the root port is in DPC handling status > and wait till the hardware and software completed the procedure. > > Signed-off-by: Ethan Zhao <haifeng.zhao@intel.com> > Tested-by: Wen Jin <wen.jin@intel.com> > Tested-by: Shanshan Zhang <ShanshanX.Zhang@intel.com> > --- > changes: > v2:align ICS code name to public doc. > v3: no change. > v4: response to Christoph's (Christoph Hellwig <hch@infradead.org>) > tip, move pci_wait_port_outdpc() to DPC driver and its declaration > to pci.h. > v5: fix building issue reported by lkp@intel.com with some config. > v6: move from [1/5] to [2/5]. > v7: no change. > v8: no change. > > drivers/pci/pci.h | 2 ++ > drivers/pci/pcie/dpc.c | 27 +++++++++++++++++++++++++++ > 2 files changed, 29 insertions(+) > > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h > index fa12f7cbc1a0..455b32187abd 100644 > --- a/drivers/pci/pci.h > +++ b/drivers/pci/pci.h > @@ -455,10 +455,12 @@ void pci_restore_dpc_state(struct pci_dev *dev); > void pci_dpc_init(struct pci_dev *pdev); > void dpc_process_error(struct pci_dev *pdev); > pci_ers_result_t dpc_reset_link(struct pci_dev *pdev); > +bool pci_wait_port_outdpc(struct pci_dev *pdev); > #else > static inline void pci_save_dpc_state(struct pci_dev *dev) {} > static inline void pci_restore_dpc_state(struct pci_dev *dev) {} > static inline void pci_dpc_init(struct pci_dev *pdev) {} > +static inline bool pci_wait_port_outdpc(struct pci_dev *pdev) { return false; } > #endif > > #ifdef CONFIG_PCI_ATS > diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c > index daa9a4153776..2e0e091ce923 100644 > --- a/drivers/pci/pcie/dpc.c > +++ b/drivers/pci/pcie/dpc.c > @@ -71,6 +71,33 @@ void pci_restore_dpc_state(struct pci_dev *dev) > pci_write_config_word(dev, dev->dpc_cap + PCI_EXP_DPC_CTL, *cap); > } > > +bool pci_wait_port_outdpc(struct pci_dev *pdev) > +{ > + u16 cap = pdev->dpc_cap, status; > + u16 loop = 0; > + > + if (!cap) { > + pci_WARN_ONCE(pdev, !cap, "No DPC capability initiated\n"); > + return false; > + } > + pci_read_config_word(pdev, cap + PCI_EXP_DPC_STATUS, &status); > + pci_dbg(pdev, "DPC status %x, cap %x\n", status, cap); > + > + while (status & PCI_EXP_DPC_STATUS_TRIGGER && loop < 100) { > + msleep(10); > + loop++; > + pci_read_config_word(pdev, cap + PCI_EXP_DPC_STATUS, &status); > + } > + > + if (!(status & PCI_EXP_DPC_STATUS_TRIGGER)) { > + pci_dbg(pdev, "Out of DPC %x, cost %d ms\n", status, loop*10); > + return true; > + } > + > + pci_dbg(pdev, "Timeout to wait port out of DPC status\n"); > + return false; > +} > + > static int dpc_wait_rp_inactive(struct pci_dev *pdev) > { > unsigned long timeout = jiffies + HZ;
-- Sathyanarayanan Kuppuswamy Linux Kernel Developer
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