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

["Mukunda,Vijendar" <vijendar.mukunda@amd.com>]

On 11/01/23 21:28, Pierre-Louis Bossart wrote:
>
> 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@amd.com>
>> Signed-off-by: Mastan Katragadda <Mastan.Katragadda@amd.com>
>> ---
>>  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?
No It's not inspired by intel code. Initially, we haven't included
pm_prepare callback. We have observed issues without
pm_prepare callback.
> 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?
Our platform supports different power modes. To support all
combinations, we have included pm_prepare callback.
>> +
>> +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?
Yes, as per our design, we need to stop the clock
before powering off.
>> +		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)
>>  };
>>