| Message ID | 20230321095031.65709-1-mika.westerberg@linux.intel.com |
|---|---|
| State | New |
| Headers | show |
| Series | PCI/PM: Wait longer after reset when active link reporting is supported | expand |
On Tue, Mar 21, 2023 at 11:50:31AM +0200, Mika Westerberg wrote: > The PCIe spec prescribes that a device may take up to 1 second to > recover from reset and this same delay is prescribed when coming out of > D3cold (as that involves reset too). The device may extend this 1 second > delay through Request Retry Status completions and we accommondate for > that in Linux with 60 second cap, only in reset code path, not in resume > code path. > > However, a device has surfaced, namely Intel Titan Ridge xHCI, which > requires longer delay also in the resume code path. For this reason make > the resume code path to use this same extended delay than with the reset > path but only after the link has come up (active link reporting is > supported) so that we do not wait longer time for devices that have > become permanently innaccessible during system sleep, e.g because they > have been removed. > > While there move the two constants from the pci.h header into pci.c as > these are not used outside of that file anymore. > > Reported-by: Chris Chiu <chris.chiu@canonical.com> > Link: https://bugzilla.kernel.org/show_bug.cgi?id=216728 > Cc: Lukas Wunner <lukas@wunner.de> > Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com> Lukas just added the "timeout" parameter with ac91e6980563 ("PCI: Unify delay handling for reset and resume"), so I'm going to look for his ack for this. After ac91e6980563, we called pci_bridge_wait_for_secondary_bus() with timeouts of either: 60s for reset (pci_bridge_secondary_bus_reset() or dpc_reset_link()), or 1s for resume (pci_pm_resume_noirq() or pci_pm_runtime_resume() via pci_pm_bridge_power_up_actions()) If I'm reading this right, the main changes of this patch are: - For slow links (<= 5 GT/s), we sleep 100ms, then previously waited up to 1s (resume) or 60s (reset) for the device to be ready. Now we will wait a max of 1s for both resume and reset. - For fast links (> 5 GT/s) we wait up to 100ms for the link to come up and fail if it does not. If the link did come up in 100ms, we previously waited up to 1s (resume) or 60s (reset). Now we will wait up to 60s for both resume and reset. So this *reduces* the time we wait for slow links after reset, and *increases* the time for fast links after resume. Right? > --- > drivers/pci/pci-driver.c | 2 +- > drivers/pci/pci.c | 51 +++++++++++++++++++++++----------------- > drivers/pci/pci.h | 16 +------------ > drivers/pci/pcie/dpc.c | 3 +-- > 4 files changed, 33 insertions(+), 39 deletions(-) > > diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c > index 57ddcc59af30..1a5ee65edb10 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, "resume", PCI_RESET_WAIT); > + pci_bridge_wait_for_secondary_bus(pci_dev, "resume"); > /* > * 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 7a67611dc5f4..f4875e5b8b29 100644 > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -64,6 +64,19 @@ struct pci_pme_device { > > #define PME_TIMEOUT 1000 /* How long between PME checks */ > > +/* > + * 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 */ > +/* > + * Devices may extend the 1 sec period through Request Retry Status completions > + * (PCIe r6.0 sec 2.3.1). The spec does not provide an upper limit, but 60 sec > + * ought to be enough for any device to become responsive. > + */ > +#define PCIE_RESET_READY_POLL_MS 60000 /* msec */ > + > static void pci_dev_d3_sleep(struct pci_dev *dev) > { > unsigned int delay_ms = max(dev->d3hot_delay, pci_pm_d3hot_delay); > @@ -4939,7 +4952,6 @@ 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 (milliseconds) > * > * Handle necessary delays before access to the devices on the secondary > * side of the bridge are permitted after D3cold to D0 transition > @@ -4952,8 +4964,7 @@ static int pci_bus_max_d3cold_delay(const struct pci_bus *bus) > * Return 0 on success or -ENOTTY if the first device on the secondary bus > * failed to become accessible. > */ > -int pci_bridge_wait_for_secondary_bus(struct pci_dev *dev, char *reset_type, > - int timeout) > +int pci_bridge_wait_for_secondary_bus(struct pci_dev *dev, char *reset_type) > { > struct pci_dev *child; > int delay; > @@ -5004,13 +5015,11 @@ int pci_bridge_wait_for_secondary_bus(struct pci_dev *dev, char *reset_type, > * speeds (gen3) we need to wait first for the data link layer to > * become active. > * > - * However, 100 ms is the minimum and the PCIe spec says the > - * software must allow at least 1s before it can determine that the > - * device that did not respond is a broken device. There is > - * evidence that 100 ms is not always enough, for example certain > - * Titan Ridge xHCI controller does not always respond to > - * configuration requests if we only wait for 100 ms (see > - * https://bugzilla.kernel.org/show_bug.cgi?id=203885). > + * However, 100 ms is the minimum and the PCIe spec says the software > + * must allow at least 1s before it can determine that the device that > + * did not respond is a broken device. Also device can take longer than > + * that to respond if it indicates so through Request Retry Status > + * completions. > * > * Therefore we wait for 100 ms and check for the device presence > * until the timeout expires. > @@ -5021,17 +5030,18 @@ int pci_bridge_wait_for_secondary_bus(struct pci_dev *dev, char *reset_type, > if (pcie_get_speed_cap(dev) <= PCIE_SPEED_5_0GT) { > pci_dbg(dev, "waiting %d ms for downstream link\n", delay); > msleep(delay); > - } else { > - pci_dbg(dev, "waiting %d ms for downstream link, after activation\n", > - delay); > - 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 -ENOTTY; > - } > + return pci_dev_wait(child, reset_type, PCI_RESET_WAIT - delay); > + } > + > + pci_dbg(dev, "waiting %d ms for downstream link, after activation\n", > + delay); > + 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 -ENOTTY; > } > > - return pci_dev_wait(child, reset_type, timeout - delay); > + return pci_dev_wait(child, reset_type, PCIE_RESET_READY_POLL_MS - delay); > } > > void pci_reset_secondary_bus(struct pci_dev *dev) > @@ -5068,8 +5078,7 @@ int pci_bridge_secondary_bus_reset(struct pci_dev *dev) > { > pcibios_reset_secondary_bus(dev); > > - return pci_bridge_wait_for_secondary_bus(dev, "bus reset", > - PCIE_RESET_READY_POLL_MS); > + return pci_bridge_wait_for_secondary_bus(dev, "bus reset"); > } > EXPORT_SYMBOL_GPL(pci_bridge_secondary_bus_reset); > > diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h > index d2c08670a20e..f2d3aeab91f4 100644 > --- a/drivers/pci/pci.h > +++ b/drivers/pci/pci.h > @@ -64,19 +64,6 @@ struct pci_cap_saved_state *pci_find_saved_ext_cap(struct pci_dev *dev, > #define PCI_PM_D3HOT_WAIT 10 /* msec */ > #define PCI_PM_D3COLD_WAIT 100 /* msec */ > > -/* > - * 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 */ > -/* > - * Devices may extend the 1 sec period through Request Retry Status completions > - * (PCIe r6.0 sec 2.3.1). The spec does not provide an upper limit, but 60 sec > - * ought to be enough for any device to become responsive. > - */ > -#define PCIE_RESET_READY_POLL_MS 60000 /* msec */ > - > void pci_update_current_state(struct pci_dev *dev, pci_power_t state); > void pci_refresh_power_state(struct pci_dev *dev); > int pci_power_up(struct pci_dev *dev); > @@ -100,8 +87,7 @@ 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_reconfigure_ltr(struct pci_dev *dev); > -int pci_bridge_wait_for_secondary_bus(struct pci_dev *dev, char *reset_type, > - int timeout); > +int pci_bridge_wait_for_secondary_bus(struct pci_dev *dev, char *reset_type); > > static inline void pci_wakeup_event(struct pci_dev *dev) > { > diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c > index a5d7c69b764e..3ceed8e3de41 100644 > --- a/drivers/pci/pcie/dpc.c > +++ b/drivers/pci/pcie/dpc.c > @@ -170,8 +170,7 @@ pci_ers_result_t dpc_reset_link(struct pci_dev *pdev) > pci_write_config_word(pdev, cap + PCI_EXP_DPC_STATUS, > PCI_EXP_DPC_STATUS_TRIGGER); > > - if (pci_bridge_wait_for_secondary_bus(pdev, "DPC", > - PCIE_RESET_READY_POLL_MS)) { > + if (pci_bridge_wait_for_secondary_bus(pdev, "DPC")) { > clear_bit(PCI_DPC_RECOVERED, &pdev->priv_flags); > ret = PCI_ERS_RESULT_DISCONNECT; > } else { > -- > 2.39.2 >
Hi Bjorn, On Wed, Mar 22, 2023 at 05:16:24PM -0500, Bjorn Helgaas wrote: > On Tue, Mar 21, 2023 at 11:50:31AM +0200, Mika Westerberg wrote: > > The PCIe spec prescribes that a device may take up to 1 second to > > recover from reset and this same delay is prescribed when coming out of > > D3cold (as that involves reset too). The device may extend this 1 second > > delay through Request Retry Status completions and we accommondate for > > that in Linux with 60 second cap, only in reset code path, not in resume > > code path. > > > > However, a device has surfaced, namely Intel Titan Ridge xHCI, which > > requires longer delay also in the resume code path. For this reason make > > the resume code path to use this same extended delay than with the reset > > path but only after the link has come up (active link reporting is > > supported) so that we do not wait longer time for devices that have > > become permanently innaccessible during system sleep, e.g because they > > have been removed. > > > > While there move the two constants from the pci.h header into pci.c as > > these are not used outside of that file anymore. > > > > Reported-by: Chris Chiu <chris.chiu@canonical.com> > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=216728 > > Cc: Lukas Wunner <lukas@wunner.de> > > Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com> > > Lukas just added the "timeout" parameter with ac91e6980563 ("PCI: > Unify delay handling for reset and resume"), so I'm going to look for > his ack for this. Of course :) > After ac91e6980563, we called pci_bridge_wait_for_secondary_bus() with > timeouts of either: > > 60s for reset (pci_bridge_secondary_bus_reset() or > dpc_reset_link()), or > > 1s for resume (pci_pm_resume_noirq() or pci_pm_runtime_resume() via > pci_pm_bridge_power_up_actions()) > > If I'm reading this right, the main changes of this patch are: > > - For slow links (<= 5 GT/s), we sleep 100ms, then previously waited > up to 1s (resume) or 60s (reset) for the device to be ready. Now > we will wait a max of 1s for both resume and reset. > > - For fast links (> 5 GT/s) we wait up to 100ms for the link to come > up and fail if it does not. If the link did come up in 100ms, we > previously waited up to 1s (resume) or 60s (reset). Now we will > wait up to 60s for both resume and reset. > > So this *reduces* the time we wait for slow links after reset, and > *increases* the time for fast links after resume. Right? Yes, this is correct.
On Thu, Mar 23, 2023 at 11:41:43AM +0200, Mika Westerberg wrote: > > After ac91e6980563, we called pci_bridge_wait_for_secondary_bus() with > > timeouts of either: > > > > 60s for reset (pci_bridge_secondary_bus_reset() or > > dpc_reset_link()), or > > > > 1s for resume (pci_pm_resume_noirq() or pci_pm_runtime_resume() via > > pci_pm_bridge_power_up_actions()) > > > > If I'm reading this right, the main changes of this patch are: > > > > - For slow links (<= 5 GT/s), we sleep 100ms, then previously waited > > up to 1s (resume) or 60s (reset) for the device to be ready. Now > > we will wait a max of 1s for both resume and reset. > > > > - For fast links (> 5 GT/s) we wait up to 100ms for the link to come > > up and fail if it does not. If the link did come up in 100ms, we > > previously waited up to 1s (resume) or 60s (reset). Now we will > > wait up to 60s for both resume and reset. > > > > So this *reduces* the time we wait for slow links after reset, and > > *increases* the time for fast links after resume. Right? > > Yes, this is correct. The reason why "fast links" is that we use the active link reporting (as it is available on such ports) to figure out whether the link trained or not and if not we come out early because it is likely that the device is not there anymore. When the link has been trained we know that the device is still there so can wait for longer it to reply. For the "slow links" this cannot be done so wait for 1s to avoid long waits if the device is already gone. I'm not entirely sure if this is fine for the reset path. I think it is but I hope Lukas/others correct me if not.
[cc += Ashok, Sathya, Ravi Kishore, Sheng Bi, Stanislav, Yang Su, Shuo Tan] On Wed, Mar 22, 2023 at 05:16:24PM -0500, Bjorn Helgaas wrote: > On Tue, Mar 21, 2023 at 11:50:31AM +0200, Mika Westerberg wrote: > > The PCIe spec prescribes that a device may take up to 1 second to > > recover from reset and this same delay is prescribed when coming out of > > D3cold (as that involves reset too). The device may extend this 1 second > > delay through Request Retry Status completions and we accommondate for > > that in Linux with 60 second cap, only in reset code path, not in resume > > code path. > > > > However, a device has surfaced, namely Intel Titan Ridge xHCI, which > > requires longer delay also in the resume code path. For this reason make > > the resume code path to use this same extended delay than with the reset > > path but only after the link has come up (active link reporting is > > supported) so that we do not wait longer time for devices that have > > become permanently innaccessible during system sleep, e.g because they > > have been removed. > > > > While there move the two constants from the pci.h header into pci.c as > > these are not used outside of that file anymore. > > > > Reported-by: Chris Chiu <chris.chiu@canonical.com> > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=216728 > > Cc: Lukas Wunner <lukas@wunner.de> > > Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com> > > Lukas just added the "timeout" parameter with ac91e6980563 ("PCI: > Unify delay handling for reset and resume"), so I'm going to look for > his ack for this. Acked-by: Lukas Wunner <lukas@wunner.de> > After ac91e6980563, we called pci_bridge_wait_for_secondary_bus() with > timeouts of either: > > 60s for reset (pci_bridge_secondary_bus_reset() or > dpc_reset_link()), or > > 1s for resume (pci_pm_resume_noirq() or pci_pm_runtime_resume() via > pci_pm_bridge_power_up_actions()) > > If I'm reading this right, the main changes of this patch are: > > - For slow links (<= 5 GT/s), we sleep 100ms, then previously waited > up to 1s (resume) or 60s (reset) for the device to be ready. Now > we will wait a max of 1s for both resume and reset. > > - For fast links (> 5 GT/s) we wait up to 100ms for the link to come > up and fail if it does not. If the link did come up in 100ms, we > previously waited up to 1s (resume) or 60s (reset). Now we will > wait up to 60s for both resume and reset. > > So this *reduces* the time we wait for slow links after reset, and > *increases* the time for fast links after resume. Right? Good point. So now the wait duration hinges on the link speed rather than reset versus resume. Before ac91e6980563 (which went into v6.3-rc1), the wait duration after a Secondary Bus Reset and a DPC-induced Hot Reset was essentially zero. And the Ponte Vecchio cards which necessitated ac91e6980563 are usually plugged into servers whose Root Ports support link speeds > 5 GT/s. So the risk of breaking anything with this change seems small. The reason why Mika is waiting only 1 second in the <= 5 GT/s case is that we don't check for the link to become active for these slower link speeds. That's because Link Active Reporting is only mandatory if the port is hotplug-capable or supports link speeds > 5 GT/s. Otherwise it's optional (PCIe r6.0.1 sec 7.5.3.6). It would be user-unfriendly to pause for 60 sec if the device does not come back after reset or resume (e.g. because it was removed) and the fact that the link is up is an indication that the device is present, but may just need a little more time to respond to Configuration Space Requests. We *could* afford the longer wait duration in the <= 5 GT/s case as well by checking if Link Active Reporting is supported and further checking if the link came up after the 100 ms delay prescribed by PCIe r6.0 sec 6.6.1. Should Link Active Reporting *not* be supported, we'd have to retain the shorter wait duration limit of 1 sec. This optimization opportunity for the <= 5 GT/s case does not have to be addressed in this patch. It could be added later on if it turns out that users do plug cards such as Ponte Vecchio into older Gen1/Gen2 Downstream Ports. (Unless Mika wants to perfect it right now.) Thanks, Lukas
Hi, On Sun, Mar 26, 2023 at 08:22:07AM +0200, Lukas Wunner wrote: > [cc += Ashok, Sathya, Ravi Kishore, Sheng Bi, Stanislav, Yang Su, Shuo Tan] > > On Wed, Mar 22, 2023 at 05:16:24PM -0500, Bjorn Helgaas wrote: > > On Tue, Mar 21, 2023 at 11:50:31AM +0200, Mika Westerberg wrote: > > > The PCIe spec prescribes that a device may take up to 1 second to > > > recover from reset and this same delay is prescribed when coming out of > > > D3cold (as that involves reset too). The device may extend this 1 second > > > delay through Request Retry Status completions and we accommondate for > > > that in Linux with 60 second cap, only in reset code path, not in resume > > > code path. > > > > > > However, a device has surfaced, namely Intel Titan Ridge xHCI, which > > > requires longer delay also in the resume code path. For this reason make > > > the resume code path to use this same extended delay than with the reset > > > path but only after the link has come up (active link reporting is > > > supported) so that we do not wait longer time for devices that have > > > become permanently innaccessible during system sleep, e.g because they > > > have been removed. > > > > > > While there move the two constants from the pci.h header into pci.c as > > > these are not used outside of that file anymore. > > > > > > Reported-by: Chris Chiu <chris.chiu@canonical.com> > > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=216728 > > > Cc: Lukas Wunner <lukas@wunner.de> > > > Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com> > > > > Lukas just added the "timeout" parameter with ac91e6980563 ("PCI: > > Unify delay handling for reset and resume"), so I'm going to look for > > his ack for this. > > Acked-by: Lukas Wunner <lukas@wunner.de> > > > > After ac91e6980563, we called pci_bridge_wait_for_secondary_bus() with > > timeouts of either: > > > > 60s for reset (pci_bridge_secondary_bus_reset() or > > dpc_reset_link()), or > > > > 1s for resume (pci_pm_resume_noirq() or pci_pm_runtime_resume() via > > pci_pm_bridge_power_up_actions()) > > > > If I'm reading this right, the main changes of this patch are: > > > > - For slow links (<= 5 GT/s), we sleep 100ms, then previously waited > > up to 1s (resume) or 60s (reset) for the device to be ready. Now > > we will wait a max of 1s for both resume and reset. > > > > - For fast links (> 5 GT/s) we wait up to 100ms for the link to come > > up and fail if it does not. If the link did come up in 100ms, we > > previously waited up to 1s (resume) or 60s (reset). Now we will > > wait up to 60s for both resume and reset. > > > > So this *reduces* the time we wait for slow links after reset, and > > *increases* the time for fast links after resume. Right? > > Good point. So now the wait duration hinges on the link speed > rather than reset versus resume. > > Before ac91e6980563 (which went into v6.3-rc1), the wait duration > after a Secondary Bus Reset and a DPC-induced Hot Reset was > essentially zero. And the Ponte Vecchio cards which necessitated > ac91e6980563 are usually plugged into servers whose Root Ports > support link speeds > 5 GT/s. So the risk of breaking anything > with this change seems small. > > The reason why Mika is waiting only 1 second in the <= 5 GT/s case > is that we don't check for the link to become active for these slower > link speeds. That's because Link Active Reporting is only mandatory > if the port is hotplug-capable or supports link speeds > 5 GT/s. > Otherwise it's optional (PCIe r6.0.1 sec 7.5.3.6). > > It would be user-unfriendly to pause for 60 sec if the device does > not come back after reset or resume (e.g. because it was removed) > and the fact that the link is up is an indication that the device > is present, but may just need a little more time to respond to > Configuration Space Requests. > > We *could* afford the longer wait duration in the <= 5 GT/s case > as well by checking if Link Active Reporting is supported and further > checking if the link came up after the 100 ms delay prescribed by > PCIe r6.0 sec 6.6.1. Should Link Active Reporting *not* be supported, > we'd have to retain the shorter wait duration limit of 1 sec. > > This optimization opportunity for the <= 5 GT/s case does not have > to be addressed in this patch. It could be added later on if it > turns out that users do plug cards such as Ponte Vecchio into older > Gen1/Gen2 Downstream Ports. (Unless Mika wants to perfect it right > now.) > No problem doing that :) I guess you mean something like the diff below, so that we use active link reporting and the longer time also for any downstream port that supports supports it, regardless of the speed. I can update the patch accordingly. diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index 36d4aaa8cea2..b507a26ffb9d 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -5027,7 +5027,8 @@ int pci_bridge_wait_for_secondary_bus(struct pci_dev *dev, char *reset_type) if (!pcie_downstream_port(dev)) return 0; - if (pcie_get_speed_cap(dev) <= PCIE_SPEED_5_0GT) { + if (!dev->link_active_reporting && + pcie_get_speed_cap(dev) <= PCIE_SPEED_5_0GT) { pci_dbg(dev, "waiting %d ms for downstream link\n", delay); msleep(delay); return pci_dev_wait(child, reset_type, PCI_RESET_WAIT - delay);
On Mon, Mar 27, 2023 at 12:42:50PM +0300, Mika Westerberg wrote: > On Sun, Mar 26, 2023 at 08:22:07AM +0200, Lukas Wunner wrote: > > On Wed, Mar 22, 2023 at 05:16:24PM -0500, Bjorn Helgaas wrote: > > > On Tue, Mar 21, 2023 at 11:50:31AM +0200, Mika Westerberg wrote: > > > After ac91e6980563, we called pci_bridge_wait_for_secondary_bus() with > > > timeouts of either: > > > > > > 60s for reset (pci_bridge_secondary_bus_reset() or > > > dpc_reset_link()), or > > > > > > 1s for resume (pci_pm_resume_noirq() or pci_pm_runtime_resume() via > > > pci_pm_bridge_power_up_actions()) > > > > > > If I'm reading this right, the main changes of this patch are: > > > > > > - For slow links (<= 5 GT/s), we sleep 100ms, then previously waited > > > up to 1s (resume) or 60s (reset) for the device to be ready. Now > > > we will wait a max of 1s for both resume and reset. > > > > > > - For fast links (> 5 GT/s) we wait up to 100ms for the link to come > > > up and fail if it does not. If the link did come up in 100ms, we > > > previously waited up to 1s (resume) or 60s (reset). Now we will > > > wait up to 60s for both resume and reset. > > > > > > So this *reduces* the time we wait for slow links after reset, and > > > *increases* the time for fast links after resume. Right? > > > > Good point. So now the wait duration hinges on the link speed > > rather than reset versus resume. > > ... > I can update the patch accordingly. If you do an update, is it possible to split into two patches so one increases the time for resume for fast links and the other decreases the time for reset on slow links? I'm thinking about potential debug efforts where it might be easier to untangle things if they are separate. Bjorn
On 3/27/23 2:42 AM, Mika Westerberg wrote: > Hi, > > On Sun, Mar 26, 2023 at 08:22:07AM +0200, Lukas Wunner wrote: >> [cc += Ashok, Sathya, Ravi Kishore, Sheng Bi, Stanislav, Yang Su, Shuo Tan] >> >> On Wed, Mar 22, 2023 at 05:16:24PM -0500, Bjorn Helgaas wrote: >>> On Tue, Mar 21, 2023 at 11:50:31AM +0200, Mika Westerberg wrote: >>>> The PCIe spec prescribes that a device may take up to 1 second to >>>> recover from reset and this same delay is prescribed when coming out of >>>> D3cold (as that involves reset too). The device may extend this 1 second >>>> delay through Request Retry Status completions and we accommondate for >>>> that in Linux with 60 second cap, only in reset code path, not in resume >>>> code path. >>>> >>>> However, a device has surfaced, namely Intel Titan Ridge xHCI, which >>>> requires longer delay also in the resume code path. For this reason make >>>> the resume code path to use this same extended delay than with the reset >>>> path but only after the link has come up (active link reporting is >>>> supported) so that we do not wait longer time for devices that have >>>> become permanently innaccessible during system sleep, e.g because they >>>> have been removed. >>>> >>>> While there move the two constants from the pci.h header into pci.c as >>>> these are not used outside of that file anymore. >>>> >>>> Reported-by: Chris Chiu <chris.chiu@canonical.com> >>>> Link: https://bugzilla.kernel.org/show_bug.cgi?id=216728 >>>> Cc: Lukas Wunner <lukas@wunner.de> >>>> Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com> >>> >>> Lukas just added the "timeout" parameter with ac91e6980563 ("PCI: >>> Unify delay handling for reset and resume"), so I'm going to look for >>> his ack for this. >> >> Acked-by: Lukas Wunner <lukas@wunner.de> >> >> >>> After ac91e6980563, we called pci_bridge_wait_for_secondary_bus() with >>> timeouts of either: >>> >>> 60s for reset (pci_bridge_secondary_bus_reset() or >>> dpc_reset_link()), or >>> >>> 1s for resume (pci_pm_resume_noirq() or pci_pm_runtime_resume() via >>> pci_pm_bridge_power_up_actions()) >>> >>> If I'm reading this right, the main changes of this patch are: >>> >>> - For slow links (<= 5 GT/s), we sleep 100ms, then previously waited >>> up to 1s (resume) or 60s (reset) for the device to be ready. Now >>> we will wait a max of 1s for both resume and reset. >>> >>> - For fast links (> 5 GT/s) we wait up to 100ms for the link to come >>> up and fail if it does not. If the link did come up in 100ms, we >>> previously waited up to 1s (resume) or 60s (reset). Now we will >>> wait up to 60s for both resume and reset. >>> >>> So this *reduces* the time we wait for slow links after reset, and >>> *increases* the time for fast links after resume. Right? >> >> Good point. So now the wait duration hinges on the link speed >> rather than reset versus resume. >> >> Before ac91e6980563 (which went into v6.3-rc1), the wait duration >> after a Secondary Bus Reset and a DPC-induced Hot Reset was >> essentially zero. And the Ponte Vecchio cards which necessitated >> ac91e6980563 are usually plugged into servers whose Root Ports >> support link speeds > 5 GT/s. So the risk of breaking anything >> with this change seems small. >> >> The reason why Mika is waiting only 1 second in the <= 5 GT/s case >> is that we don't check for the link to become active for these slower >> link speeds. That's because Link Active Reporting is only mandatory >> if the port is hotplug-capable or supports link speeds > 5 GT/s. >> Otherwise it's optional (PCIe r6.0.1 sec 7.5.3.6). >> >> It would be user-unfriendly to pause for 60 sec if the device does >> not come back after reset or resume (e.g. because it was removed) >> and the fact that the link is up is an indication that the device >> is present, but may just need a little more time to respond to >> Configuration Space Requests. >> >> We *could* afford the longer wait duration in the <= 5 GT/s case >> as well by checking if Link Active Reporting is supported and further >> checking if the link came up after the 100 ms delay prescribed by >> PCIe r6.0 sec 6.6.1. Should Link Active Reporting *not* be supported, >> we'd have to retain the shorter wait duration limit of 1 sec. >> >> This optimization opportunity for the <= 5 GT/s case does not have >> to be addressed in this patch. It could be added later on if it >> turns out that users do plug cards such as Ponte Vecchio into older >> Gen1/Gen2 Downstream Ports. (Unless Mika wants to perfect it right >> now.) >> > > No problem doing that :) I guess you mean something like the diff below, > so that we use active link reporting and the longer time also for any > downstream port that supports supports it, regardless of the speed. > > I can update the patch accordingly. > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > index 36d4aaa8cea2..b507a26ffb9d 100644 > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -5027,7 +5027,8 @@ int pci_bridge_wait_for_secondary_bus(struct pci_dev *dev, char *reset_type) > if (!pcie_downstream_port(dev)) > return 0; > > - if (pcie_get_speed_cap(dev) <= PCIE_SPEED_5_0GT) { > + if (!dev->link_active_reporting && > + pcie_get_speed_cap(dev) <= PCIE_SPEED_5_0GT) { Do we still need speed check? It looks like we can take this path if link active reporting is not supported. > pci_dbg(dev, "waiting %d ms for downstream link\n", delay); > msleep(delay); > return pci_dev_wait(child, reset_type, PCI_RESET_WAIT - delay);
On Mon, Mar 27, 2023 at 09:40:50AM -0500, Bjorn Helgaas wrote: > On Mon, Mar 27, 2023 at 12:42:50PM +0300, Mika Westerberg wrote: > > On Sun, Mar 26, 2023 at 08:22:07AM +0200, Lukas Wunner wrote: > > > On Wed, Mar 22, 2023 at 05:16:24PM -0500, Bjorn Helgaas wrote: > > > > On Tue, Mar 21, 2023 at 11:50:31AM +0200, Mika Westerberg wrote: > > > > > After ac91e6980563, we called pci_bridge_wait_for_secondary_bus() with > > > > timeouts of either: > > > > > > > > 60s for reset (pci_bridge_secondary_bus_reset() or > > > > dpc_reset_link()), or > > > > > > > > 1s for resume (pci_pm_resume_noirq() or pci_pm_runtime_resume() via > > > > pci_pm_bridge_power_up_actions()) > > > > > > > > If I'm reading this right, the main changes of this patch are: > > > > > > > > - For slow links (<= 5 GT/s), we sleep 100ms, then previously waited > > > > up to 1s (resume) or 60s (reset) for the device to be ready. Now > > > > we will wait a max of 1s for both resume and reset. > > > > > > > > - For fast links (> 5 GT/s) we wait up to 100ms for the link to come > > > > up and fail if it does not. If the link did come up in 100ms, we > > > > previously waited up to 1s (resume) or 60s (reset). Now we will > > > > wait up to 60s for both resume and reset. > > > > > > > > So this *reduces* the time we wait for slow links after reset, and > > > > *increases* the time for fast links after resume. Right? > > > > > > Good point. So now the wait duration hinges on the link speed > > > rather than reset versus resume. > > > ... > > > I can update the patch accordingly. > > If you do an update, is it possible to split into two patches so one > increases the time for resume for fast links and the other decreases > the time for reset on slow links? I'm thinking about potential debug > efforts where it might be easier to untangle things if they are > separate. Yes, sure.
On Mon, Mar 27, 2023 at 08:08:21AM -0700, Sathyanarayanan Kuppuswamy wrote: > > > On 3/27/23 2:42 AM, Mika Westerberg wrote: > > Hi, > > > > On Sun, Mar 26, 2023 at 08:22:07AM +0200, Lukas Wunner wrote: > >> [cc += Ashok, Sathya, Ravi Kishore, Sheng Bi, Stanislav, Yang Su, Shuo Tan] > >> > >> On Wed, Mar 22, 2023 at 05:16:24PM -0500, Bjorn Helgaas wrote: > >>> On Tue, Mar 21, 2023 at 11:50:31AM +0200, Mika Westerberg wrote: > >>>> The PCIe spec prescribes that a device may take up to 1 second to > >>>> recover from reset and this same delay is prescribed when coming out of > >>>> D3cold (as that involves reset too). The device may extend this 1 second > >>>> delay through Request Retry Status completions and we accommondate for > >>>> that in Linux with 60 second cap, only in reset code path, not in resume > >>>> code path. > >>>> > >>>> However, a device has surfaced, namely Intel Titan Ridge xHCI, which > >>>> requires longer delay also in the resume code path. For this reason make > >>>> the resume code path to use this same extended delay than with the reset > >>>> path but only after the link has come up (active link reporting is > >>>> supported) so that we do not wait longer time for devices that have > >>>> become permanently innaccessible during system sleep, e.g because they > >>>> have been removed. > >>>> > >>>> While there move the two constants from the pci.h header into pci.c as > >>>> these are not used outside of that file anymore. > >>>> > >>>> Reported-by: Chris Chiu <chris.chiu@canonical.com> > >>>> Link: https://bugzilla.kernel.org/show_bug.cgi?id=216728 > >>>> Cc: Lukas Wunner <lukas@wunner.de> > >>>> Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com> > >>> > >>> Lukas just added the "timeout" parameter with ac91e6980563 ("PCI: > >>> Unify delay handling for reset and resume"), so I'm going to look for > >>> his ack for this. > >> > >> Acked-by: Lukas Wunner <lukas@wunner.de> > >> > >> > >>> After ac91e6980563, we called pci_bridge_wait_for_secondary_bus() with > >>> timeouts of either: > >>> > >>> 60s for reset (pci_bridge_secondary_bus_reset() or > >>> dpc_reset_link()), or > >>> > >>> 1s for resume (pci_pm_resume_noirq() or pci_pm_runtime_resume() via > >>> pci_pm_bridge_power_up_actions()) > >>> > >>> If I'm reading this right, the main changes of this patch are: > >>> > >>> - For slow links (<= 5 GT/s), we sleep 100ms, then previously waited > >>> up to 1s (resume) or 60s (reset) for the device to be ready. Now > >>> we will wait a max of 1s for both resume and reset. > >>> > >>> - For fast links (> 5 GT/s) we wait up to 100ms for the link to come > >>> up and fail if it does not. If the link did come up in 100ms, we > >>> previously waited up to 1s (resume) or 60s (reset). Now we will > >>> wait up to 60s for both resume and reset. > >>> > >>> So this *reduces* the time we wait for slow links after reset, and > >>> *increases* the time for fast links after resume. Right? > >> > >> Good point. So now the wait duration hinges on the link speed > >> rather than reset versus resume. > >> > >> Before ac91e6980563 (which went into v6.3-rc1), the wait duration > >> after a Secondary Bus Reset and a DPC-induced Hot Reset was > >> essentially zero. And the Ponte Vecchio cards which necessitated > >> ac91e6980563 are usually plugged into servers whose Root Ports > >> support link speeds > 5 GT/s. So the risk of breaking anything > >> with this change seems small. > >> > >> The reason why Mika is waiting only 1 second in the <= 5 GT/s case > >> is that we don't check for the link to become active for these slower > >> link speeds. That's because Link Active Reporting is only mandatory > >> if the port is hotplug-capable or supports link speeds > 5 GT/s. > >> Otherwise it's optional (PCIe r6.0.1 sec 7.5.3.6). > >> > >> It would be user-unfriendly to pause for 60 sec if the device does > >> not come back after reset or resume (e.g. because it was removed) > >> and the fact that the link is up is an indication that the device > >> is present, but may just need a little more time to respond to > >> Configuration Space Requests. > >> > >> We *could* afford the longer wait duration in the <= 5 GT/s case > >> as well by checking if Link Active Reporting is supported and further > >> checking if the link came up after the 100 ms delay prescribed by > >> PCIe r6.0 sec 6.6.1. Should Link Active Reporting *not* be supported, > >> we'd have to retain the shorter wait duration limit of 1 sec. > >> > >> This optimization opportunity for the <= 5 GT/s case does not have > >> to be addressed in this patch. It could be added later on if it > >> turns out that users do plug cards such as Ponte Vecchio into older > >> Gen1/Gen2 Downstream Ports. (Unless Mika wants to perfect it right > >> now.) > >> > > > > No problem doing that :) I guess you mean something like the diff below, > > so that we use active link reporting and the longer time also for any > > downstream port that supports supports it, regardless of the speed. > > > > I can update the patch accordingly. > > > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > > index 36d4aaa8cea2..b507a26ffb9d 100644 > > --- a/drivers/pci/pci.c > > +++ b/drivers/pci/pci.c > > @@ -5027,7 +5027,8 @@ int pci_bridge_wait_for_secondary_bus(struct pci_dev *dev, char *reset_type) > > if (!pcie_downstream_port(dev)) > > return 0; > > > > - if (pcie_get_speed_cap(dev) <= PCIE_SPEED_5_0GT) { > > + if (!dev->link_active_reporting && > > + pcie_get_speed_cap(dev) <= PCIE_SPEED_5_0GT) { > > Do we still need speed check? It looks like we can take this path > if link active reporting is not supported. Good question, the spec only talks about the speed here: With a Downstream Port that does not support Link speeds greater than 5.0 GT/s, software must wait a minimum of 100 ms before sending a Configuration Request to the device immediately below that Port. but then again if the port supports active link reporting we will end up waiting more than the 100 ms above anyway so the minimum requirement should be met.
diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c index 57ddcc59af30..1a5ee65edb10 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, "resume", PCI_RESET_WAIT); + pci_bridge_wait_for_secondary_bus(pci_dev, "resume"); /* * 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 7a67611dc5f4..f4875e5b8b29 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -64,6 +64,19 @@ struct pci_pme_device { #define PME_TIMEOUT 1000 /* How long between PME checks */ +/* + * 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 */ +/* + * Devices may extend the 1 sec period through Request Retry Status completions + * (PCIe r6.0 sec 2.3.1). The spec does not provide an upper limit, but 60 sec + * ought to be enough for any device to become responsive. + */ +#define PCIE_RESET_READY_POLL_MS 60000 /* msec */ + static void pci_dev_d3_sleep(struct pci_dev *dev) { unsigned int delay_ms = max(dev->d3hot_delay, pci_pm_d3hot_delay); @@ -4939,7 +4952,6 @@ 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 (milliseconds) * * Handle necessary delays before access to the devices on the secondary * side of the bridge are permitted after D3cold to D0 transition @@ -4952,8 +4964,7 @@ static int pci_bus_max_d3cold_delay(const struct pci_bus *bus) * Return 0 on success or -ENOTTY if the first device on the secondary bus * failed to become accessible. */ -int pci_bridge_wait_for_secondary_bus(struct pci_dev *dev, char *reset_type, - int timeout) +int pci_bridge_wait_for_secondary_bus(struct pci_dev *dev, char *reset_type) { struct pci_dev *child; int delay; @@ -5004,13 +5015,11 @@ int pci_bridge_wait_for_secondary_bus(struct pci_dev *dev, char *reset_type, * speeds (gen3) we need to wait first for the data link layer to * become active. * - * However, 100 ms is the minimum and the PCIe spec says the - * software must allow at least 1s before it can determine that the - * device that did not respond is a broken device. There is - * evidence that 100 ms is not always enough, for example certain - * Titan Ridge xHCI controller does not always respond to - * configuration requests if we only wait for 100 ms (see - * https://bugzilla.kernel.org/show_bug.cgi?id=203885). + * However, 100 ms is the minimum and the PCIe spec says the software + * must allow at least 1s before it can determine that the device that + * did not respond is a broken device. Also device can take longer than + * that to respond if it indicates so through Request Retry Status + * completions. * * Therefore we wait for 100 ms and check for the device presence * until the timeout expires. @@ -5021,17 +5030,18 @@ int pci_bridge_wait_for_secondary_bus(struct pci_dev *dev, char *reset_type, if (pcie_get_speed_cap(dev) <= PCIE_SPEED_5_0GT) { pci_dbg(dev, "waiting %d ms for downstream link\n", delay); msleep(delay); - } else { - pci_dbg(dev, "waiting %d ms for downstream link, after activation\n", - delay); - 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 -ENOTTY; - } + return pci_dev_wait(child, reset_type, PCI_RESET_WAIT - delay); + } + + pci_dbg(dev, "waiting %d ms for downstream link, after activation\n", + delay); + 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 -ENOTTY; } - return pci_dev_wait(child, reset_type, timeout - delay); + return pci_dev_wait(child, reset_type, PCIE_RESET_READY_POLL_MS - delay); } void pci_reset_secondary_bus(struct pci_dev *dev) @@ -5068,8 +5078,7 @@ int pci_bridge_secondary_bus_reset(struct pci_dev *dev) { pcibios_reset_secondary_bus(dev); - return pci_bridge_wait_for_secondary_bus(dev, "bus reset", - PCIE_RESET_READY_POLL_MS); + return pci_bridge_wait_for_secondary_bus(dev, "bus reset"); } EXPORT_SYMBOL_GPL(pci_bridge_secondary_bus_reset); diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h index d2c08670a20e..f2d3aeab91f4 100644 --- a/drivers/pci/pci.h +++ b/drivers/pci/pci.h @@ -64,19 +64,6 @@ struct pci_cap_saved_state *pci_find_saved_ext_cap(struct pci_dev *dev, #define PCI_PM_D3HOT_WAIT 10 /* msec */ #define PCI_PM_D3COLD_WAIT 100 /* msec */ -/* - * 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 */ -/* - * Devices may extend the 1 sec period through Request Retry Status completions - * (PCIe r6.0 sec 2.3.1). The spec does not provide an upper limit, but 60 sec - * ought to be enough for any device to become responsive. - */ -#define PCIE_RESET_READY_POLL_MS 60000 /* msec */ - void pci_update_current_state(struct pci_dev *dev, pci_power_t state); void pci_refresh_power_state(struct pci_dev *dev); int pci_power_up(struct pci_dev *dev); @@ -100,8 +87,7 @@ 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_reconfigure_ltr(struct pci_dev *dev); -int pci_bridge_wait_for_secondary_bus(struct pci_dev *dev, char *reset_type, - int timeout); +int pci_bridge_wait_for_secondary_bus(struct pci_dev *dev, char *reset_type); static inline void pci_wakeup_event(struct pci_dev *dev) { diff --git a/drivers/pci/pcie/dpc.c b/drivers/pci/pcie/dpc.c index a5d7c69b764e..3ceed8e3de41 100644 --- a/drivers/pci/pcie/dpc.c +++ b/drivers/pci/pcie/dpc.c @@ -170,8 +170,7 @@ pci_ers_result_t dpc_reset_link(struct pci_dev *pdev) pci_write_config_word(pdev, cap + PCI_EXP_DPC_STATUS, PCI_EXP_DPC_STATUS_TRIGGER); - if (pci_bridge_wait_for_secondary_bus(pdev, "DPC", - PCIE_RESET_READY_POLL_MS)) { + if (pci_bridge_wait_for_secondary_bus(pdev, "DPC")) { clear_bit(PCI_DPC_RECOVERED, &pdev->priv_flags); ret = PCI_ERS_RESULT_DISCONNECT; } else {
The PCIe spec prescribes that a device may take up to 1 second to recover from reset and this same delay is prescribed when coming out of D3cold (as that involves reset too). The device may extend this 1 second delay through Request Retry Status completions and we accommondate for that in Linux with 60 second cap, only in reset code path, not in resume code path. However, a device has surfaced, namely Intel Titan Ridge xHCI, which requires longer delay also in the resume code path. For this reason make the resume code path to use this same extended delay than with the reset path but only after the link has come up (active link reporting is supported) so that we do not wait longer time for devices that have become permanently innaccessible during system sleep, e.g because they have been removed. While there move the two constants from the pci.h header into pci.c as these are not used outside of that file anymore. Reported-by: Chris Chiu <chris.chiu@canonical.com> Link: https://bugzilla.kernel.org/show_bug.cgi?id=216728 Cc: Lukas Wunner <lukas@wunner.de> Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com> --- drivers/pci/pci-driver.c | 2 +- drivers/pci/pci.c | 51 +++++++++++++++++++++++----------------- drivers/pci/pci.h | 16 +------------ drivers/pci/pcie/dpc.c | 3 +-- 4 files changed, 33 insertions(+), 39 deletions(-)