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author | Takashi Iwai <tiwai@suse.de> | 2005-11-17 17:26:09 +0100 |
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committer | Jaroslav Kysela <perex@suse.cz> | 2006-01-03 12:28:55 +0100 |
commit | 5fe76e4dc60a2c3ff9b1143f5275a953db685e26 (patch) | |
tree | f54acdb029f429bf8c0068ed964a1216fbe614d3 /Documentation/sound | |
parent | a4efc230c60ad15584e723755316e67b3c708d67 (diff) | |
download | linux-5fe76e4dc60a2c3ff9b1143f5275a953db685e26.tar.bz2 |
[ALSA] document - Update PM support
Modules: Documentation
Update the description about the PCI PM support.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Diffstat (limited to 'Documentation/sound')
-rw-r--r-- | Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl | 185 |
1 files changed, 146 insertions, 39 deletions
diff --git a/Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl b/Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl index f2e59fe802bd..4963d83d1511 100644 --- a/Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl +++ b/Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl @@ -18,8 +18,8 @@ </affiliation> </author> - <date>October 6, 2005</date> - <edition>0.3.5</edition> + <date>November 17, 2005</date> + <edition>0.3.6</edition> <abstract> <para> @@ -2329,9 +2329,14 @@ struct _snd_pcm_runtime { <constant>PAUSE</constant> bit means that the pcm supports the <quote>pause</quote> operation, while the <constant>RESUME</constant> bit means that the pcm supports - the <quote>suspend/resume</quote> operation. If these flags - are set, the <structfield>trigger</structfield> callback below - must handle the corresponding commands. + the full <quote>suspend/resume</quote> operation. + If <constant>PAUSE</constant> flag is set, + the <structfield>trigger</structfield> callback below + must handle the corresponding (pause push/release) commands. + The suspend/resume trigger commands can be defined even without + <constant>RESUME</constant> flag. See <link + linkend="power-management"><citetitle> + Power Management</citetitle></link> section for details. </para> <para> @@ -2903,8 +2908,8 @@ struct _snd_pcm_runtime { </para> <para> - When the pcm supports the suspend/resume operation - (i.e. <constant>SNDRV_PCM_INFO_RESUME</constant> flag is set), + When the pcm supports the suspend/resume operation, + regardless of full or partial suspend/resume support, <constant>SUSPEND</constant> and <constant>RESUME</constant> commands must be handled, too. These commands are issued when the power-management status is @@ -2913,6 +2918,8 @@ struct _snd_pcm_runtime { do suspend and resume of the pcm substream, and usually, they are identical with <constant>STOP</constant> and <constant>START</constant> commands, respectively. + See <link linkend="power-management"><citetitle> + Power Management</citetitle></link> section for details. </para> <para> @@ -5483,22 +5490,60 @@ struct _snd_pcm_runtime { <constant>CONFIG_PM</constant>. </para> + <para> + If the driver supports the suspend/resume + <emphasis>fully</emphasis>, that is, the device can be + properly resumed to the status at the suspend is called, + you can set <constant>SNDRV_PCM_INFO_RESUME</constant> flag + to pcm info field. Usually, this is possible when the + registers of ths chip can be safely saved and restored to the + RAM. If this is set, the trigger callback is called with + <constant>SNDRV_PCM_TRIGGER_RESUME</constant> after resume + callback is finished. + </para> + + <para> + Even if the driver doesn't support PM fully but only the + partial suspend/resume is possible, it's still worthy to + implement suspend/resume callbacks. In such a case, applications + would reset the status by calling + <function>snd_pcm_prepare()</function> and restart the stream + appropriately. Hence, you can define suspend/resume callbacks + below but don't set <constant>SNDRV_PCM_INFO_RESUME</constant> + info flag to the PCM. + </para> + + <para> + Note that the trigger with SUSPEND can be always called when + <function>snd_pcm_suspend_all</function> is called, + regardless of <constant>SNDRV_PCM_INFO_RESUME</constant> flag. + The <constant>RESUME</constant> flag affects only the behavior + of <function>snd_pcm_resume()</function>. + (Thus, in theory, + <constant>SNDRV_PCM_TRIGGER_RESUME</constant> isn't needed + to be handled in the trigger callback when no + <constant>SNDRV_PCM_INFO_RESUME</constant> flag is set. But, + it's better to keep it for compatibility reason.) + </para> <para> - ALSA provides the common power-management layer. Each card driver - needs to have only low-level suspend and resume callbacks. + In the earlier version of ALSA drivers, a common + power-management layer was provided, but it has been removed. + The driver needs to define the suspend/resume hooks according to + the bus the device is assigned. In the case of PCI driver, the + callbacks look like below: <informalexample> <programlisting> <![CDATA[ #ifdef CONFIG_PM - static int snd_my_suspend(struct snd_card *card, pm_message_t state) + static int snd_my_suspend(struct pci_dev *pci, pm_message_t state) { - .... // do things for suspsend + .... /* do things for suspsend */ return 0; } - static int snd_my_resume(struct snd_card *card) + static int snd_my_resume(struct pci_dev *pci) { - .... // do things for suspsend + .... /* do things for suspsend */ return 0; } #endif @@ -5511,11 +5556,18 @@ struct _snd_pcm_runtime { The scheme of the real suspend job is as following. <orderedlist> - <listitem><para>Retrieve the chip data from pm_private_data field.</para></listitem> + <listitem><para>Retrieve the card and the chip data.</para></listitem> + <listitem><para>Call <function>snd_power_change_state()</function> with + <constant>SNDRV_CTL_POWER_D3hot</constant> to change the + power status.</para></listitem> <listitem><para>Call <function>snd_pcm_suspend_all()</function> to suspend the running PCM streams.</para></listitem> + <listitem><para>If AC97 codecs are used, call + <function>snd_ac97_resume()</function> for each codec.</para></listitem> <listitem><para>Save the register values if necessary.</para></listitem> <listitem><para>Stop the hardware if necessary.</para></listitem> - <listitem><para>Disable the PCI device by calling <function>pci_disable_device()</function>.</para></listitem> + <listitem><para>Disable the PCI device by calling + <function>pci_disable_device()</function>. Then, call + <function>pci_save_state()</function> at last.</para></listitem> </orderedlist> </para> @@ -5525,18 +5577,24 @@ struct _snd_pcm_runtime { <informalexample> <programlisting> <![CDATA[ - static int mychip_suspend(struct snd_card *card, pm_message_t state) + static int mychip_suspend(strut pci_dev *pci, pm_message_t state) { /* (1) */ - struct mychip *chip = card->pm_private_data; + struct snd_card *card = pci_get_drvdata(pci); + struct mychip *chip = card->private_data; /* (2) */ - snd_pcm_suspend_all(chip->pcm); + snd_power_change_state(card, SNDRV_CTL_POWER_D3hot); /* (3) */ - snd_mychip_save_registers(chip); + snd_pcm_suspend_all(chip->pcm); /* (4) */ - snd_mychip_stop_hardware(chip); + snd_ac97_suspend(chip->ac97); /* (5) */ - pci_disable_device(chip->pci); + snd_mychip_save_registers(chip); + /* (6) */ + snd_mychip_stop_hardware(chip); + /* (7) */ + pci_disable_device(pci); + pci_save_state(pci); return 0; } ]]> @@ -5548,14 +5606,17 @@ struct _snd_pcm_runtime { The scheme of the real resume job is as following. <orderedlist> - <listitem><para>Retrieve the chip data from pm_private_data field.</para></listitem> - <listitem><para>Enable the pci device again by calling - <function>pci_enable_device()</function>.</para></listitem> + <listitem><para>Retrieve the card and the chip data.</para></listitem> + <listitem><para>Set up PCI. First, call <function>pci_restore_state()</function>. + Then enable the pci device again by calling <function>pci_enable_device()</function>. + Call <function>pci_set_master()</function> if necessary, too.</para></listitem> <listitem><para>Re-initialize the chip.</para></listitem> <listitem><para>Restore the saved registers if necessary.</para></listitem> <listitem><para>Resume the mixer, e.g. calling <function>snd_ac97_resume()</function>.</para></listitem> <listitem><para>Restart the hardware (if any).</para></listitem> + <listitem><para>Call <function>snd_power_change_state()</function> with + <constant>SNDRV_CTL_POWER_D0</constant> to notify the processes.</para></listitem> </orderedlist> </para> @@ -5565,12 +5626,15 @@ struct _snd_pcm_runtime { <informalexample> <programlisting> <![CDATA[ - static void mychip_resume(struct mychip *chip) + static int mychip_resume(struct pci_dev *pci) { /* (1) */ - struct mychip *chip = card->pm_private_data; + struct snd_card *card = pci_get_drvdata(pci); + struct mychip *chip = card->private_data; /* (2) */ - pci_enable_device(chip->pci); + pci_restore_state(pci); + pci_enable_device(pci); + pci_set_master(pci); /* (3) */ snd_mychip_reinit_chip(chip); /* (4) */ @@ -5579,6 +5643,8 @@ struct _snd_pcm_runtime { snd_ac97_resume(chip->ac97); /* (6) */ snd_mychip_restart_chip(chip); + /* (7) */ + snd_power_change_state(card, SNDRV_CTL_POWER_D0); return 0; } ]]> @@ -5587,8 +5653,48 @@ struct _snd_pcm_runtime { </para> <para> - OK, we have all callbacks now. Let's set up them now. In the - initialization of the card, add the following: + As shown in the above, it's better to save registers after + suspending the PCM operations via + <function>snd_pcm_suspend_all()</function> or + <function>snd_pcm_suspend()</function>. It means that the PCM + streams are already stoppped when the register snapshot is + taken. But, remind that you don't have to restart the PCM + stream in the resume callback. It'll be restarted via + trigger call with <constant>SNDRV_PCM_TRIGGER_RESUME</constant> + when necessary. + </para> + + <para> + OK, we have all callbacks now. Let's set them up. In the + initialization of the card, make sure that you can get the chip + data from the card instance, typically via + <structfield>private_data</structfield> field, in case you + created the chip data individually. + + <informalexample> + <programlisting> +<![CDATA[ + static int __devinit snd_mychip_probe(struct pci_dev *pci, + const struct pci_device_id *pci_id) + { + .... + struct snd_card *card; + struct mychip *chip; + .... + card = snd_card_new(index[dev], id[dev], THIS_MODULE, NULL); + .... + chip = kzalloc(sizeof(*chip), GFP_KERNEL); + .... + card->private_data = chip; + .... + } +]]> + </programlisting> + </informalexample> + + When you created the chip data with + <function>snd_card_new()</function>, it's anyway accessible + via <structfield>private_data</structfield> field. <informalexample> <programlisting> @@ -5600,30 +5706,28 @@ struct _snd_pcm_runtime { struct snd_card *card; struct mychip *chip; .... - snd_card_set_pm_callback(card, snd_my_suspend, snd_my_resume, chip); + card = snd_card_new(index[dev], id[dev], THIS_MODULE, + sizeof(struct mychip)); + .... + chip = card->private_data; .... } ]]> </programlisting> </informalexample> - Here you don't have to put ifdef CONFIG_PM around, since it's already - checked in the header and expanded to empty if not needed. </para> <para> - If you need a space for saving the registers, you'll need to - allocate the buffer for it here, too, since it would be fatal + If you need a space for saving the registers, allocate the + buffer for it here, too, since it would be fatal if you cannot allocate a memory in the suspend phase. The allocated buffer should be released in the corresponding destructor. </para> <para> - And next, set suspend/resume callbacks to the pci_driver, - This can be done by passing a macro SND_PCI_PM_CALLBACKS - in the pci_driver struct. This macro is expanded to the correct - (global) callbacks if CONFIG_PM is set. + And next, set suspend/resume callbacks to the pci_driver. <informalexample> <programlisting> @@ -5633,7 +5737,10 @@ struct _snd_pcm_runtime { .id_table = snd_my_ids, .probe = snd_my_probe, .remove = __devexit_p(snd_my_remove), - SND_PCI_PM_CALLBACKS + #ifdef CONFIG_PM + .suspend = snd_my_suspend, + .resume = snd_my_resume, + #endif }; ]]> </programlisting> |