On 12/31/22 10:33 AM, Lukas Wunner wrote: > Sheng Bi reports that pci_bridge_secondary_bus_reset() may fail to wait > for devices on the secondary bus to become accessible after reset: > > Although it does call pci_dev_wait(), it erroneously passes the bridge's > pci_dev rather than that of a child. The bridge of course is always > accessible while its secondary bus is reset, so pci_dev_wait() returns > immediately. > > Sheng Bi proposes introducing a new pci_bridge_secondary_bus_wait() > function which is called from pci_bridge_secondary_bus_reset(): > > https://lore.kernel.org/linux-pci/20220523171517.32407-1-windy.bi.enflame@xxxxxxxxx/ > > However we already have pci_bridge_wait_for_secondary_bus() which does > almost exactly what we need. So far it's only called on resume from > D3cold (which implies a Fundamental Reset per PCIe r6.0 sec 5.8). > Re-using it for Secondary Bus Resets is a leaner and more rational > approach than introducing a new function. > > That only requires a few minor tweaks: > > - Amend pci_bridge_wait_for_secondary_bus() to await accessibility of > the first device on the secondary bus by calling pci_dev_wait() after > performing the prescribed delays. pci_dev_wait() needs two parameters, > a reset reason and a timeout, which callers must now pass to > pci_bridge_wait_for_secondary_bus(). The timeout is 1 sec for resume > (PCIe r6.0 sec 6.6.1) and 60 sec for reset (commit 821cdad5c46c ("PCI: > Wait up to 60 seconds for device to become ready after FLR")). > > - Amend pci_bridge_wait_for_secondary_bus() to return 0 on success or > -ENOTTY on error for consumption by pci_bridge_secondary_bus_reset(). > > - Drop an unnecessary 1 sec delay from pci_reset_secondary_bus() which > is now performed by pci_bridge_wait_for_secondary_bus(). A static > delay this long is only necessary for Conventional PCI, so modern > PCIe systems benefit from shorter reset times as a side effect. > > Fixes: 6b2f1351af56 ("PCI: Wait for device to become ready after secondary bus reset") > Reported-by: Sheng Bi <windy.bi.enflame@xxxxxxxxx> > Tested-by: Ravi Kishore Koppuravuri <ravi.kishore.koppuravuri@xxxxxxxxx> > Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx> > Cc: stable@xxxxxxxxxxxxxxx # v4.17+ > Cc: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> > --- Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx> > drivers/pci/pci-driver.c | 2 +- > drivers/pci/pci.c | 50 ++++++++++++++++++---------------------- > drivers/pci/pci.h | 3 ++- > 3 files changed, 25 insertions(+), 30 deletions(-) > > diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c > index a2ceeacc33eb..02e84c87f41a 100644 > --- a/drivers/pci/pci-driver.c > +++ b/drivers/pci/pci-driver.c > @@ -572,7 +572,7 @@ static void pci_pm_default_resume_early(struct pci_dev *pci_dev) > > static void pci_pm_bridge_power_up_actions(struct pci_dev *pci_dev) > { > - pci_bridge_wait_for_secondary_bus(pci_dev); > + pci_bridge_wait_for_secondary_bus(pci_dev, "resume", 1000); > /* > * When powering on a bridge from D3cold, the whole hierarchy may be > * powered on into D0uninitialized state, resume them to give them a > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > index f43f3e84f634..b0b49243a908 100644 > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -4948,24 +4948,31 @@ static int pci_bus_max_d3cold_delay(const struct pci_bus *bus) > /** > * pci_bridge_wait_for_secondary_bus - Wait for secondary bus to be accessible > * @dev: PCI bridge > + * @reset_type: reset type in human-readable form > + * @timeout: maximum time to wait for devices on secondary bus > * > * Handle necessary delays before access to the devices on the secondary > - * side of the bridge are permitted after D3cold to D0 transition. > + * side of the bridge are permitted after D3cold to D0 transition > + * or Conventional Reset. > * > * For PCIe this means the delays in PCIe 5.0 section 6.6.1. For > * conventional PCI it means Tpvrh + Trhfa specified in PCI 3.0 section > * 4.3.2. > + * > + * Return 0 on success or -ENOTTY if the first device on the secondary bus > + * failed to become accessible. > */ > -void pci_bridge_wait_for_secondary_bus(struct pci_dev *dev) > +int pci_bridge_wait_for_secondary_bus(struct pci_dev *dev, char *reset_type, > + int timeout) > { > struct pci_dev *child; > int delay; > > if (pci_dev_is_disconnected(dev)) > - return; > + return 0; > > if (!pci_is_bridge(dev)) > - return; > + return 0; > > down_read(&pci_bus_sem); > > @@ -4977,14 +4984,14 @@ void pci_bridge_wait_for_secondary_bus(struct pci_dev *dev) > */ > if (!dev->subordinate || list_empty(&dev->subordinate->devices)) { > up_read(&pci_bus_sem); > - return; > + return 0; > } > > /* Take d3cold_delay requirements into account */ > delay = pci_bus_max_d3cold_delay(dev->subordinate); > if (!delay) { > up_read(&pci_bus_sem); > - return; > + return 0; > } > > child = list_first_entry(&dev->subordinate->devices, struct pci_dev, > @@ -4993,14 +5000,12 @@ void pci_bridge_wait_for_secondary_bus(struct pci_dev *dev) > > /* > * Conventional PCI and PCI-X we need to wait Tpvrh + Trhfa before > - * accessing the device after reset (that is 1000 ms + 100 ms). In > - * practice this should not be needed because we don't do power > - * management for them (see pci_bridge_d3_possible()). > + * accessing the device after reset (that is 1000 ms + 100 ms). > */ > if (!pci_is_pcie(dev)) { > pci_dbg(dev, "waiting %d ms for secondary bus\n", 1000 + delay); > msleep(1000 + delay); > - return; > + return 0; > } > > /* > @@ -5017,11 +5022,11 @@ void pci_bridge_wait_for_secondary_bus(struct pci_dev *dev) > * configuration requests if we only wait for 100 ms (see > * https://bugzilla.kernel.org/show_bug.cgi?id=203885). > * > - * Therefore we wait for 100 ms and check for the device presence. > - * If it is still not present give it an additional 100 ms. > + * Therefore we wait for 100 ms and check for the device presence > + * until the timeout expires. > */ > if (!pcie_downstream_port(dev)) > - return; > + return 0; > > if (pcie_get_speed_cap(dev) <= PCIE_SPEED_5_0GT) { > pci_dbg(dev, "waiting %d ms for downstream link\n", delay); > @@ -5032,14 +5037,11 @@ void pci_bridge_wait_for_secondary_bus(struct pci_dev *dev) > if (!pcie_wait_for_link_delay(dev, true, delay)) { > /* Did not train, no need to wait any further */ > pci_info(dev, "Data Link Layer Link Active not set in 1000 msec\n"); > - return; > + return -ENOTTY; > } > } > > - if (!pci_device_is_present(child)) { > - pci_dbg(child, "waiting additional %d ms to become accessible\n", delay); > - msleep(delay); > - } > + return pci_dev_wait(child, reset_type, timeout - delay); > } > > void pci_reset_secondary_bus(struct pci_dev *dev) > @@ -5058,15 +5060,6 @@ void pci_reset_secondary_bus(struct pci_dev *dev) > > ctrl &= ~PCI_BRIDGE_CTL_BUS_RESET; > pci_write_config_word(dev, PCI_BRIDGE_CONTROL, ctrl); > - > - /* > - * Trhfa for conventional PCI is 2^25 clock cycles. > - * Assuming a minimum 33MHz clock this results in a 1s > - * delay before we can consider subordinate devices to > - * be re-initialized. PCIe has some ways to shorten this, > - * but we don't make use of them yet. > - */ > - ssleep(1); > } > > void __weak pcibios_reset_secondary_bus(struct pci_dev *dev) > @@ -5085,7 +5078,8 @@ int pci_bridge_secondary_bus_reset(struct pci_dev *dev) > { > pcibios_reset_secondary_bus(dev); > > - return pci_dev_wait(dev, "bus reset", PCIE_RESET_READY_POLL_MS); > + return pci_bridge_wait_for_secondary_bus(dev, "bus reset", > + PCIE_RESET_READY_POLL_MS); > } > EXPORT_SYMBOL_GPL(pci_bridge_secondary_bus_reset); > > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h > index 9ed3b5550043..40758248dd80 100644 > --- a/drivers/pci/pci.h > +++ b/drivers/pci/pci.h > @@ -86,8 +86,9 @@ void pci_msi_init(struct pci_dev *dev); > void pci_msix_init(struct pci_dev *dev); > bool pci_bridge_d3_possible(struct pci_dev *dev); > void pci_bridge_d3_update(struct pci_dev *dev); > -void pci_bridge_wait_for_secondary_bus(struct pci_dev *dev); > void pci_bridge_reconfigure_ltr(struct pci_dev *dev); > +int pci_bridge_wait_for_secondary_bus(struct pci_dev *dev, char *reset_type, > + int timeout); > > static inline void pci_wakeup_event(struct pci_dev *dev) > { -- Sathyanarayanan Kuppuswamy Linux Kernel Developer
