From: Pierre-Louis Bossart pierre-louis.bossart@linux.intel.com

The power down sequence sets the link_up flag as false outside of the mutex_lock. This is potentially unsafe.

In additional the flow in that sequence can be improved by first testing if the link was powered, setting the link_up flag as false and proceeding with the power down. In case the CPA bits cannot be cleared, we only flag an error since we cannot deal with interrupts any longer.

Signed-off-by: Pierre-Louis Bossart pierre-louis.bossart@linux.intel.com Reviewed-by: Ranjani Sridharan ranjani.sridharan@linux.intel.com Signed-off-by: Bard Liao yung-chuan.liao@linux.intel.com --- drivers/soundwire/intel.c | 23 +++++++++++++---------- 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/soundwire/intel.c b/drivers/soundwire/intel.c index 9794bc222fb5..808dda1380c2 100644 --- a/drivers/soundwire/intel.c +++ b/drivers/soundwire/intel.c @@ -538,12 +538,14 @@ static int intel_link_power_down(struct sdw_intel *sdw)

mutex_lock(sdw->link_res->shim_lock);

- intel_shim_master_ip_to_glue(sdw); - if (!(*shim_mask & BIT(link_id))) dev_err(sdw->cdns.dev, "%s: Unbalanced power-up/down calls\n", __func__);

+ sdw->cdns.link_up = false; + + intel_shim_master_ip_to_glue(sdw); + *shim_mask &= ~BIT(link_id);

if (!*shim_mask) { @@ -560,18 +562,19 @@ static int intel_link_power_down(struct sdw_intel *sdw) link_control &= spa_mask;

ret = intel_clear_bit(shim, SDW_SHIM_LCTL, link_control, cpa_mask); + if (ret < 0) { + dev_err(sdw->cdns.dev, "%s: could not power down link\n", __func__); + + /* + * we leave the sdw->cdns.link_up flag as false since we've disabled + * the link at this point and cannot handle interrupts any longer. + */ + } }

mutex_unlock(sdw->link_res->shim_lock);

- if (ret < 0) { - dev_err(sdw->cdns.dev, "%s: could not power down link\n", __func__); - - return ret; - } - - sdw->cdns.link_up = false; - return 0; + return ret; }

static void intel_shim_sync_arm(struct sdw_intel *sdw)

From: Pierre-Louis Bossart pierre-louis.bossart@linux.intel.com

Intel stress tests reported issues with the clock stop mode, specifically when trying to do a system suspend while the link is already pm_runtime suspended.

In this case, we need to disable the shim wake, but when the PCI parent device is also pm_runtime suspended the SHIM registers are not accessible.

Since this is an invalid corner case, this patch suggests a pm_runtime resume of the entire bus to full power (parent+child devices) before the system suspend so that the shim wake can be disabled.

Unlike the suspend operation, the .prepare callbacks are propagated from root device to leaf devices. By adding a .prepare callback at the SoundWire link level, we can double-check the pm_runtime status of the device as well as its parent PCI device. When the problematic configuration is detected, the device is pm_runtime resumed - which by construction also resume its parent.

An additional loop is added to resume all child devices. In theory we only need to restart the link, but doing so will also cause the physical devices to synchronize and re-initialize, while their Linux devices remain pm_runtime suspended. It's simpler to make sure the codec devices are fully resumed so that we don't have to deal with zombie states.

This additional loop could have been avoided by adding a .prepare callback in SoundWire codec drivers. Functionally this would have been equivalent. The rationale for implementing a loop at the link level is only to reduce the amount of code required to deal at the codec level with an Intel corner case - in other words keep codec drivers independent from Intel platform-specific programming sequences.

BugLink: https://github.com/thesofproject/linux/issues/2606 Signed-off-by: Pierre-Louis Bossart pierre-louis.bossart@linux.intel.com Signed-off-by: Bard Liao yung-chuan.liao@linux.intel.com --- drivers/soundwire/intel.c | 105 +++++++++++++++++++++++++++++++++----- 1 file changed, 93 insertions(+), 12 deletions(-)

diff --git a/drivers/soundwire/intel.c b/drivers/soundwire/intel.c index 8b42053b171f..f66fcbc33a2f 100644 --- a/drivers/soundwire/intel.c +++ b/drivers/soundwire/intel.c @@ -1596,6 +1596,87 @@ int intel_link_process_wakeen_event(struct auxiliary_device *auxdev) * PM calls */

+static int intel_resume_child_device(struct device *dev, void *data) +{ + int ret; + struct sdw_slave *slave = dev_to_sdw_dev(dev); + + if (!slave->probed) { + dev_dbg(dev, "%s: skipping device, no probed driver\n", __func__); + return 0; + } + if (!slave->dev_num_sticky) { + dev_dbg(dev, "%s: skipping device, never detected on bus\n", __func__); + return 0; + } + + ret = pm_request_resume(dev); + if (ret < 0) + dev_err(dev, "%s: pm_request_resume failed: %d\n", __func__, ret); + + return ret; +} + +static int __maybe_unused intel_pm_prepare(struct device *dev) +{ + struct sdw_cdns *cdns = dev_get_drvdata(dev); + struct sdw_intel *sdw = cdns_to_intel(cdns); + struct sdw_bus *bus = &cdns->bus; + u32 clock_stop_quirks; + int ret = 0; + + if (bus->prop.hw_disabled || !sdw->startup_done) { + dev_dbg(dev, "SoundWire master %d is disabled or not-started, ignoring\n", + bus->link_id); + return 0; + } + + clock_stop_quirks = sdw->link_res->clock_stop_quirks; + + if (pm_runtime_suspended(dev) && + pm_runtime_suspended(dev->parent) && + ((clock_stop_quirks & SDW_INTEL_CLK_STOP_BUS_RESET) || + !clock_stop_quirks)) { + /* + * if we've enabled clock stop, and the parent is suspended, the SHIM registers + * are not accessible and the shim wake cannot be disabled. + * The only solution is to resume the entire bus to full power + */ + + /* + * If any operation in this block fails, we keep going since we don't want + * to prevent system suspend from happening and errors should be recoverable + * on resume. + */ + + /* + * first resume the device for this link. This will also by construction + * resume the PCI parent device. + */ + ret = pm_request_resume(dev); + if (ret < 0) { + dev_err(dev, "%s: pm_request_resume failed: %d\n", __func__, ret); + return 0; + } + + /* + * Continue resuming the entire bus (parent + child devices) to exit + * the clock stop mode. If there are no devices connected on this link + * this is a no-op. + * The resume to full power could have been implemented with a .prepare + * step in SoundWire codec drivers. This would however require a lot + * of code to handle an Intel-specific corner case. It is simpler in + * practice to add a loop at the link level. + */ + ret = device_for_each_child(bus->dev, NULL, intel_resume_child_device); + + if (ret < 0) + dev_err(dev, "%s: intel_resume_child_device failed: %d\n", __func__, ret); + } + + return 0; +} + static int __maybe_unused intel_suspend(struct device *dev) { struct sdw_cdns *cdns = dev_get_drvdata(dev); @@ -1615,19 +1696,18 @@ static int __maybe_unused intel_suspend(struct device *dev)

clock_stop_quirks = sdw->link_res->clock_stop_quirks;

- if ((clock_stop_quirks & SDW_INTEL_CLK_STOP_BUS_RESET || - !clock_stop_quirks) && - !pm_runtime_suspended(dev->parent)) { + if ((clock_stop_quirks & SDW_INTEL_CLK_STOP_BUS_RESET) || + !clock_stop_quirks) {

- /* - * if we've enabled clock stop, and the parent - * is still active, disable shim wake. The - * SHIM registers are not accessible if the - * parent is already pm_runtime suspended so - * it's too late to change that configuration - */ - - intel_shim_wake(sdw, false); + if (pm_runtime_suspended(dev->parent)) { + /* + * paranoia check: this should not happen with the .prepare + * resume to full power + */ + dev_err(dev, "%s: invalid config: parent is suspended\n", __func__); + } else { + intel_shim_wake(sdw, false); + } }

return 0; @@ -1992,6 +2072,7 @@ static int __maybe_unused intel_resume_runtime(struct device *dev) }

static const struct dev_pm_ops intel_pm = { + .prepare = intel_pm_prepare, SET_SYSTEM_SLEEP_PM_OPS(intel_suspend, intel_resume) SET_RUNTIME_PM_OPS(intel_suspend_runtime, intel_resume_runtime, NULL) };