Re: [PATCH 17/19] soundwire: amd: add pm_prepare callback and pm ops support

[Pierre-Louis Bossart]

On 1/11/23 03:02, Vijendar Mukunda wrote:
> Add pm_prepare callback and System level pm ops support for
> AMD master driver.
> 
> Signed-off-by: Vijendar Mukunda <Vijendar.Mukunda@xxxxxxx>
> Signed-off-by: Mastan Katragadda <Mastan.Katragadda@xxxxxxx>
> ---
>  drivers/soundwire/amd_master.c | 76 ++++++++++++++++++++++++++++++++++
>  1 file changed, 76 insertions(+)
> 
> diff --git a/drivers/soundwire/amd_master.c b/drivers/soundwire/amd_master.c
> index 2fd77a673c22..f4478cc17aac 100644
> --- a/drivers/soundwire/amd_master.c
> +++ b/drivers/soundwire/amd_master.c
> @@ -1552,6 +1552,80 @@ static int amd_sdwc_clock_stop_exit(struct amd_sdwc_ctrl *ctrl)
>  	return 0;
>  }
>  
> +static int amd_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, "skipping device, no probed driver\n");
> +		return 0;
> +	}
> +	if (!slave->dev_num_sticky) {
> +		dev_dbg(dev, "skipping device, never detected on bus\n");
> +		return 0;
> +	}
> +
> +	if (!pm_runtime_suspended(dev))
> +		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 amd_pm_prepare(struct device *dev)
> +{
> +	struct amd_sdwc_ctrl *ctrl = dev_get_drvdata(dev);
> +	struct sdw_bus *bus = &ctrl->bus;
> +	int ret;
> +
> +	if (bus->prop.hw_disabled || !ctrl->startup_done) {
> +		dev_dbg(bus->dev, "SoundWire master %d is disabled or not-started, ignoring\n",
> +			bus->link_id);
> +		return 0;
> +	}
> +	ret = device_for_each_child(bus->dev, NULL, amd_resume_child_device);
> +	if (ret < 0)
> +		dev_err(dev, "%s: amd_resume_child_device failed: %d\n", __func__, ret);
> +	if (pm_runtime_suspended(dev) && ctrl->power_mode_mask & AMD_SDW_CLK_STOP_MODE) {
> +		ret = pm_request_resume(dev);
> +		if (ret < 0) {
> +			dev_err(bus->dev, "pm_request_resume failed: %d\n", ret);
> +			return 0;
> +		}
> +	}
> +	return 0;
> +}

This seems to be inspired by the Intel code, but is this necessary here?

For Intel, we saw cases where we had to pm_resume before doing a system
suspend, otherwise the hardware was in a bad state.

Do you actually need to do so, or is is possible to do a system suspend
when the clock is stopped.

And in the case where the bus is in 'power-off' mode, do you actually
need to resume at all?

> +
> +static int __maybe_unused amd_suspend(struct device *dev)
> +{
> +	struct amd_sdwc_ctrl *ctrl = dev_get_drvdata(dev);
> +	struct sdw_bus *bus = &ctrl->bus;
> +	int ret;
> +
> +	if (bus->prop.hw_disabled || !ctrl->startup_done) {
> +		dev_dbg(bus->dev, "SoundWire master %d is disabled or not-started, ignoring\n",
> +			bus->link_id);
> +		return 0;
> +	}
> +
> +	if (ctrl->power_mode_mask & AMD_SDW_CLK_STOP_MODE) {
> +		ret = amd_sdwc_clock_stop(ctrl);
> +		if (ret)
> +			return ret;
> +	} else if (ctrl->power_mode_mask & AMD_SDW_POWER_OFF_MODE) {
> +		ret = amd_sdwc_clock_stop(ctrl);

do you actually need to stop the clock before powering-off? This seems
counter intuitive and not so useful?

> +		if (ret)
> +			return ret;
> +		ret = amd_deinit_sdw_controller(ctrl);
> +		if (ret)
> +			return ret;
> +	}
> +	return 0;
> +}
> +
>  static int __maybe_unused amd_suspend_runtime(struct device *dev)
>  {
>  	struct amd_sdwc_ctrl *ctrl = dev_get_drvdata(dev);
> @@ -1638,6 +1712,8 @@ static int __maybe_unused amd_resume_runtime(struct device *dev)
>  }
>  
>  static const struct dev_pm_ops amd_pm = {
> +	.prepare = amd_pm_prepare,
> +	SET_SYSTEM_SLEEP_PM_OPS(amd_suspend, amd_resume_runtime)
>  	SET_RUNTIME_PM_OPS(amd_suspend_runtime, amd_resume_runtime, NULL)
>  };
>