Re: [PATCH V2] ASoC: fix hdmi codec driver contest in S3

From: "Yang, Libin" <libin.yang@intel.com>
To: Takashi Iwai <tiwai@suse.de>
Cc: "alsa-devel@alsa-project.org" <alsa-devel@alsa-project.org>,
	"broonie@kernel.org" <broonie@kernel.org>
Subject: Re: [PATCH V2] ASoC: fix hdmi codec driver contest in S3
Date: Mon, 25 Mar 2019 06:51:11 +0000	[thread overview]
Message-ID: <96A12704CE18D347B625EE2D4A099D19527FAAA5@SHSMSX103.ccr.corp.intel.com> (raw)
In-Reply-To: <s5hbm22psfz.wl-tiwai@suse.de>

Hi Takashi,

>-----Original Message-----
>From: Takashi Iwai [mailto:tiwai@suse.de]
>Sent: Saturday, March 23, 2019 4:26 AM
>To: Yang, Libin <libin.yang@intel.com>
>Cc: alsa-devel@alsa-project.org; broonie@kernel.org
>Subject: Re: [alsa-devel] [PATCH V2] ASoC: fix hdmi codec driver contest in S3
>
>On Fri, 22 Mar 2019 12:46:25 +0100,
>Yang, Libin wrote:
>>
>> Hi Takashi,
>>
>> >> >
>> >> >On Fri, 22 Mar 2019 07:24:56 +0100, libin.yang@intel.com wrote:
>> >> >>
>> >> >> From: Libin Yang <libin.yang@intel.com>
>> >> >>
>> >> >> In S3, there is a contest between dapm event and getting display
>power.
>> >> >>
>> >> >> When resume, the sequence is:
>> >> >>
>> >> >> hdac_hdmi_runtime_resume()
>> >> >>   => snd_hdac_display_power()
>> >> >> hdac_hdmi_xxx_widget_event()
>> >> >>
>> >> >> The hdac_hdmi_xxx_widget_event() are based on the power being on.
>> >> >> Otherwise, the operation on the codec register will fail.
>> >> >>
>> >> >> However, in snd_hdac_display_power(), it may sleep because of
>> >> >> the
>> >> >> mutex_lock() in display driver. In this case,
>> >> >> hdac_hdmi_xxx_widget_event() will be called before the power is on.
>> >> >>
>> >> >> Let's not operate the registers and wait for the power in
>> >> >> hdac_hdmi_xxx_widget_event()
>> >> >>
>> >> >> Signed-off-by: Libin Yang <libin.yang@intel.com>
>> >> >
>> >> >IMO the workaround looks a bit too fragile.  The substantial
>> >> >problem is the race between codec and DAPM.  Can this be
>> >> >controlled better, e.g. by defining the proper PM dependency?  I
>> >> >thought we may rearrange the PM topology dynamically.
>> >>
>> >> It seems codec and DAPM is OK so far. Codec resume will be called
>> >> firstly and then DAPM. But in HDMI codec runtime resume, it will
>> >> call snd_hdac_display_power(). This function will try to get a mutex_lock.
>> >> If it fails to get the lock, it will sleep. This will cause dapm
>> >> event handler to be called before audio power domain in display is
>> >> on in the HDMI
>> >driver.
>> >
>> >It implies that the calls are racy.  If they have to be called in
>> >some order, they have to be serialized in a more better way than inserting
>a random delay...
>>
>> Yes. The code does seem to be misleading. What do you think of using
>> something like "wait_for_complete()"? This will be more readable.
>
>Well, maybe we should create a proper device link for assuring the PM
>dependency instead?  Then PM core will take care of everything like that ugly
>stuff.

Thanks for the suggestion. I did some investigation based on your suggestion
today. Below is the result on my sof platform:
There are 3 devices we concerned in this case:
machine_device: this is the device of the machine, its parent is pci_device
hdmi_device: this is the device of the hdmi codec, its parent is pci_device
pci_device: this is the device of the pci

When resume, pci_device will be resumed firstly, and then machine_device 
and hdmi_device.
When machine_device is resumed, it will schedule a work to call the
xxx_event(). So the xxx_event() will be run later.
When hdmi_device is resumed, it will try to turn on display power. However,
it may sleep if it can't get the mutex_lock. 

If hdmi_device sleeps, xxx_event() will be called firstly. However, this is wrong,
because xxx_event() depends on the display power.

So if we want to make sure machine_device resume is called always after
hdmi_device resume, we must set hdmi_device being the parent machine_device.
This seems a little weird because codecs are different for different platforms.
And what's more, one platform may have several codecs. It's hard to say which
codec should be the parent.

There is another solution I can figure out. We can do power on display power
in each xxx_event() manually. However, this may not be a very good solution.
There are several xxx_event() functions. So each time power on, the 
display power will be turned on several time. 

As we can make sure that display power is turned on already or will be turned
on very soon in the future. What about we just wait for completion of the 
display power on?

Regards,
Libin

>
>
>Takashi
>
>>
>> Regards,
>> Libin
>>
>> >
>> >
>> >thanks,
>> >
>> >Takashi
>> >
>> >>
>> >> Regards,
>> >> Libin
>> >>
>> >> >
>> >> >
>> >> >thanks,
>> >> >
>> >> >Takashi
>> >> >
>> >> >> ---
>> >> >>  sound/soc/codecs/hdac_hdmi.c | 36
>> >> >> ++++++++++++++++++++++++++++++++++++
>> >> >>  1 file changed, 36 insertions(+)
>> >> >>
>> >> >> diff --git a/sound/soc/codecs/hdac_hdmi.c
>> >> >> b/sound/soc/codecs/hdac_hdmi.c index 5eeb0fe..3c5c122 100644
>> >> >> --- a/sound/soc/codecs/hdac_hdmi.c
>> >> >> +++ b/sound/soc/codecs/hdac_hdmi.c
>> >> >> @@ -144,6 +144,7 @@ struct hdac_hdmi_priv {
>> >> >>  	int num_pin;
>> >> >>  	int num_cvt;
>> >> >>  	int num_ports;
>> >> >> +	int display_power;	/* 0: power off; 1 power on */
>> >> >>  	struct mutex pin_mutex;
>> >> >>  	struct hdac_chmap chmap;
>> >> >>  	struct hdac_hdmi_drv_data *drv_data; @@ -742,12 +743,27
>@@
>> >> >static
>> >> >> void hdac_hdmi_set_amp(struct hdac_device *hdev,
>> >> >>
>	AC_VERB_SET_AMP_GAIN_MUTE,
>> >> >val);  }
>> >> >>
>> >> >> +static int wait_for_display_power(struct hdac_hdmi_priv *hdmi) {
>> >> >> +	int i = 0;
>> >> >> +
>> >> >> +	/* sleep for totally 80ms ~ 200ms should be enough */
>> >> >> +	while (i < 40) {
>> >> >> +		if (!hdmi->display_power)
>> >> >> +			usleep_range(2000, 5000);
>> >> >> +		else
>> >> >> +			return 0;
>> >> >> +		i++;
>> >> >> +	}
>> >> >> +	return -EAGAIN;
>> >> >> +}
>> >> >>
>> >> >>  static int hdac_hdmi_pin_output_widget_event(struct
>> >> >snd_soc_dapm_widget *w,
>> >> >>  					struct snd_kcontrol *kc, int
>event)  {
>> >> >>  	struct hdac_hdmi_port *port = w->priv;
>> >> >>  	struct hdac_device *hdev = dev_to_hdac_dev(w->dapm->dev);
>> >> >> +	struct hdac_hdmi_priv *hdmi = hdev_to_hdmi_priv(hdev);
>> >> >>  	struct hdac_hdmi_pcm *pcm;
>> >> >>
>> >> >>  	dev_dbg(&hdev->dev, "%s: widget: %s event: %x\n", @@ -
>757,6
>> >> >+773,11
>> >> >> @@ static int hdac_hdmi_pin_output_widget_event(struct
>> >> >snd_soc_dapm_widget *w,
>> >> >>  	if (!pcm)
>> >> >>  		return -EIO;
>> >> >>
>> >> >> +	if (wait_for_display_power(hdmi)) {
>> >> >> +		dev_err(&hdev->dev, "%s: hdmi power is not ready\n",
>> >> >__func__);
>> >> >> +		return -EAGAIN;
>> >> >> +	}
>> >> >> +
>> >> >>  	/* set the device if pin is mst_capable */
>> >> >>  	if (hdac_hdmi_port_select_set(hdev, port) < 0)
>> >> >>  		return -EIO;
>> >> >> @@ -803,6 +824,11 @@ static int
>> >> >hdac_hdmi_cvt_output_widget_event(struct snd_soc_dapm_widget *w,
>> >> >>  	if (!pcm)
>> >> >>  		return -EIO;
>> >> >>
>> >> >> +	if (wait_for_display_power(hdmi)) {
>> >> >> +		dev_err(&hdev->dev, "%s: hdmi power is not ready\n",
>> >> >__func__);
>> >> >> +		return -EAGAIN;
>> >> >> +	}
>> >> >> +
>> >> >>  	switch (event) {
>> >> >>  	case SND_SOC_DAPM_PRE_PMU:
>> >> >>  		hdac_hdmi_set_power_state(hdev, cvt->nid,
>AC_PWRST_D0);
>> >> >@@ -840,6
>> >> >> +866,7 @@ static int hdac_hdmi_pin_mux_widget_event(struct
>> >> >> snd_soc_dapm_widget *w,  {
>> >> >>  	struct hdac_hdmi_port *port = w->priv;
>> >> >>  	struct hdac_device *hdev = dev_to_hdac_dev(w->dapm->dev);
>> >> >> +	struct hdac_hdmi_priv *hdmi = hdev_to_hdmi_priv(hdev);
>> >> >>  	int mux_idx;
>> >> >>
>> >> >>  	dev_dbg(&hdev->dev, "%s: widget: %s event: %x\n", @@ -
>850,6
>> >> >+877,11
>> >> >> @@ static int hdac_hdmi_pin_mux_widget_event(struct
>> >> >> snd_soc_dapm_widget *w,
>> >> >>
>> >> >>  	mux_idx = dapm_kcontrol_get_value(kc);
>> >> >>
>> >> >> +	if (wait_for_display_power(hdmi)) {
>> >> >> +		dev_err(&hdev->dev, "%s: hdmi power is not ready\n",
>> >> >__func__);
>> >> >> +		return -EAGAIN;
>> >> >> +	}
>> >> >> +
>> >> >>  	/* set the device if pin is mst_capable */
>> >> >>  	if (hdac_hdmi_port_select_set(hdev, port) < 0)
>> >> >>  		return -EIO;
>> >> >> @@ -2068,6 +2100,7 @@ static int
>> >> >> hdac_hdmi_runtime_suspend(struct device *dev)  {
>> >> >>  	struct hdac_device *hdev = dev_to_hdac_dev(dev);
>> >> >>  	struct hdac_bus *bus = hdev->bus;
>> >> >> +	struct hdac_hdmi_priv *hdmi = hdev_to_hdmi_priv(hdev);
>> >> >>  	struct hdac_ext_link *hlink = NULL;
>> >> >>
>> >> >>  	dev_dbg(dev, "Enter: %s\n", __func__); @@ -2095,6 +2128,7
>@@
>> >> >static
>> >> >> int hdac_hdmi_runtime_suspend(struct device *dev)
>> >> >>  	snd_hdac_ext_bus_link_put(bus, hlink);
>> >> >>
>> >> >>  	snd_hdac_display_power(bus, hdev->addr, false);
>> >> >> +	hdmi->display_power = 0;
>> >> >>
>> >> >>  	return 0;
>> >> >>  }
>> >> >> @@ -2102,6 +2136,7 @@ static int
>> >> >> hdac_hdmi_runtime_suspend(struct device *dev)  static int
>> >> >> hdac_hdmi_runtime_resume(struct device
>> >> >> *dev) {
>> >> >>  	struct hdac_device *hdev = dev_to_hdac_dev(dev);
>> >> >> +	struct hdac_hdmi_priv *hdmi = hdev_to_hdmi_priv(hdev);
>> >> >>  	struct hdac_bus *bus = hdev->bus;
>> >> >>  	struct hdac_ext_link *hlink = NULL;
>> >> >>
>> >> >> @@ -2128,6 +2163,7 @@ static int
>hdac_hdmi_runtime_resume(struct
>> >> >device *dev)
>> >> >>  	snd_hdac_codec_read(hdev, hdev->afg, 0,
>> >> >	AC_VERB_SET_POWER_STATE,
>> >> >>
>	AC_PWRST_D0);
>> >> >>
>> >> >> +	hdmi->display_power = 1;
>> >> >>  	return 0;
>> >> >>  }
>> >> >>  #else
>> >> >> --
>> >> >> 2.7.4
>> >> >>
>> >> >> _______________________________________________
>> >> >> Alsa-devel mailing list
>> >> >> Alsa-devel@alsa-project.org
>> >> >> https://mailman.alsa-project.org/mailman/listinfo/alsa-devel
>> >> >>
>> >>
>>