From: Lukas Wunner lukas@wunner.de
commit ac91e6980563ed53afadd925fa6585ffd2bc4a2c upstream.
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@gm...
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")). Introduce a PCI_RESET_WAIT macro for the 1 sec timeout.
- 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") Link: https://lore.kernel.org/r/da77c92796b99ec568bd070cbe4725074a117038.167376951... Reported-by: Sheng Bi windy.bi.enflame@gmail.com Tested-by: Ravi Kishore Koppuravuri ravi.kishore.koppuravuri@intel.com Signed-off-by: Lukas Wunner lukas@wunner.de Signed-off-by: Bjorn Helgaas bhelgaas@google.com Reviewed-by: Mika Westerberg mika.westerberg@linux.intel.com Reviewed-by: Kuppuswamy Sathyanarayanan sathyanarayanan.kuppuswamy@linux.intel.com Cc: stable@vger.kernel.org # v4.17+ Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/pci/pci-driver.c | 4 +-- drivers/pci/pci.c | 54 ++++++++++++++++++++--------------------------- drivers/pci/pci.h | 10 +++++++- 3 files changed, 35 insertions(+), 33 deletions(-)
--- a/drivers/pci/pci-driver.c +++ b/drivers/pci/pci-driver.c @@ -946,7 +946,7 @@ static int pci_pm_resume_noirq(struct de pcie_pme_root_status_cleanup(pci_dev);
if (!skip_bus_pm && prev_state == PCI_D3cold) - pci_bridge_wait_for_secondary_bus(pci_dev); + pci_bridge_wait_for_secondary_bus(pci_dev, "resume", PCI_RESET_WAIT);
if (pci_has_legacy_pm_support(pci_dev)) return pci_legacy_resume_early(dev); @@ -1355,7 +1355,7 @@ static int pci_pm_runtime_resume(struct pci_fixup_device(pci_fixup_resume, pci_dev);
if (prev_state == PCI_D3cold) - pci_bridge_wait_for_secondary_bus(pci_dev); + pci_bridge_wait_for_secondary_bus(pci_dev, "resume", PCI_RESET_WAIT);
if (pm && pm->runtime_resume) rc = pm->runtime_resume(dev); --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -4483,7 +4483,7 @@ static int pci_dev_wait(struct pci_dev * return -ENOTTY; }
- if (delay > 1000) + if (delay > PCI_RESET_WAIT) pci_info(dev, "not ready %dms after %s; waiting\n", delay - 1, reset_type);
@@ -4492,7 +4492,7 @@ static int pci_dev_wait(struct pci_dev * pci_read_config_dword(dev, PCI_COMMAND, &id); }
- if (delay > 1000) + if (delay > PCI_RESET_WAIT) pci_info(dev, "ready %dms after %s\n", delay - 1, reset_type);
@@ -4727,24 +4727,31 @@ static int pci_bus_max_d3cold_delay(cons /** * 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 (milliseconds) * * 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);
@@ -4756,14 +4763,14 @@ void pci_bridge_wait_for_secondary_bus(s */ 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, @@ -4772,14 +4779,12 @@ void pci_bridge_wait_for_secondary_bus(s
/* * 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; }
/* @@ -4796,11 +4801,11 @@ void pci_bridge_wait_for_secondary_bus(s * 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); @@ -4810,14 +4815,11 @@ void pci_bridge_wait_for_secondary_bus(s delay); if (!pcie_wait_for_link_delay(dev, true, delay)) { /* Did not train, no need to wait any further */ - 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) @@ -4836,15 +4838,6 @@ void pci_reset_secondary_bus(struct pci_
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) @@ -4863,7 +4856,8 @@ int pci_bridge_secondary_bus_reset(struc { 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);
--- a/drivers/pci/pci.h +++ b/drivers/pci/pci.h @@ -47,6 +47,13 @@ int pci_bus_error_reset(struct pci_dev * #define PCI_PM_D3COLD_WAIT 100 #define PCI_PM_BUS_WAIT 50
+/* + * Following exit from Conventional Reset, devices must be ready within 1 sec + * (PCIe r6.0 sec 6.6.1). A D3cold to D0 transition implies a Conventional + * Reset (PCIe r6.0 sec 5.8). + */ +#define PCI_RESET_WAIT 1000 /* msec */ + /** * struct pci_platform_pm_ops - Firmware PM callbacks * @@ -107,7 +114,8 @@ void pci_allocate_cap_save_buffers(struc void pci_free_cap_save_buffers(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); +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) {