[PATCH 3/4] soundwire: intel: exit clock stop mode on system suspend

[Vinod Koul]

On 27-07-21, 13:56, Bard Liao wrote:
> From: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
> 
> Intel validation reported an issue where the HW_RST self-clearing bit
> is not cleared in hardware, which as a ripple effect creates issues
> with the clock stop mode.
> 
> This happens is a specific sequence where the Intel manager is
> pm_runtime suspended with the clock-stop mode enabled. During the
> system suspend, we currently do nothing, which can lead to potential
> issues on system resume and the following pm_runtime suspend,
> depending on the hardware state.
> 
> This patch suggests a full resume (parent+child devices) if the
> clock-stop mode is used. This may require extra time but will make the
> suspend/resume flows completely symmetric. This also removes a race
> condition where we could not access SHIM registers if the parent was
> suspended as well. Resuming the link also resumes the parent by
> construction.
> 
> BugLink: https://github.com/thesofproject/linux/issues/2606
> Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
> Reviewed-by: Ranjani Sridharan <ranjani.sridharan at linux.intel.com>
> Signed-off-by: Bard Liao <yung-chuan.liao at linux.intel.com>
> ---
>  drivers/soundwire/intel.c | 65 +++++++++++++++++++++++++++++++++++++++
>  1 file changed, 65 insertions(+)
> 
> diff --git a/drivers/soundwire/intel.c b/drivers/soundwire/intel.c
> index 46d1645cb7fe..9d05e158fe0e 100644
> --- a/drivers/soundwire/intel.c
> +++ b/drivers/soundwire/intel.c
> @@ -1527,6 +1527,70 @@ 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 ((clock_stop_quirks & SDW_INTEL_CLK_STOP_BUS_RESET) ||
> +	    !clock_stop_quirks) {
> +		/*
> +		 * Try to resume the entire bus (parent + child devices) to exit
> +		 * the clock stop mode. If this fails, we keep going since we don't want
> +		 * to prevent system suspend from happening and errors should be recoverable
> +		 * on resume.
> +		 */
> +		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);
> +
> +		/*
> +		 * in the case where a link was started but does not have anything connected,
> +		 * we still need to resume to keep link power up/down sequences balanced.
> +		 * This is a no-op if a child device was present, since resuming the child
> +		 * device would also resume the parent
> +		 */
> +		ret = pm_request_resume(dev);

I am not sure of this patch yet, maybe I am comprehending it..

1. In above you are calling resume of child devices first and then intel
device, which sounds reverse, should you not resume intel device first
and then child (codec devices) ?

2. What about when resume is invoked by the core for the child devices.
That would be called in the PM resume flow, so why do it here?

> +		if (ret < 0)
> +			dev_err(dev, "%s: pm_request_resume failed: %d\n", __func__, ret);
> +	}
> +
> +	return 0;
> +}
> +
>  static int __maybe_unused intel_suspend(struct device *dev)
>  {
>  	struct sdw_cdns *cdns = dev_get_drvdata(dev);
> @@ -1923,6 +1987,7 @@ 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)
>  };
> -- 
> 2.17.1

-- 
~Vinod