From 5fe76e4dc60a2c3ff9b1143f5275a953db685e26 Mon Sep 17 00:00:00 2001 From: Takashi Iwai Date: Thu, 17 Nov 2005 17:26:09 +0100 Subject: [ALSA] document - Update PM support Modules: Documentation Update the description about the PCI PM support. Signed-off-by: Takashi Iwai --- .../sound/alsa/DocBook/writing-an-alsa-driver.tmpl | 185 ++++++++++++++++----- 1 file changed, 146 insertions(+), 39 deletions(-) (limited to 'Documentation/sound') diff --git a/Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl b/Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl index f2e59fe..4963d83 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 @@ - October 6, 2005 - 0.3.5 + November 17, 2005 + 0.3.6 @@ -2329,9 +2329,14 @@ struct _snd_pcm_runtime { PAUSE bit means that the pcm supports the pause operation, while the RESUME bit means that the pcm supports - the suspend/resume operation. If these flags - are set, the trigger callback below - must handle the corresponding commands. + the full suspend/resume operation. + If PAUSE flag is set, + the trigger callback below + must handle the corresponding (pause push/release) commands. + The suspend/resume trigger commands can be defined even without + RESUME flag. See + Power Management section for details. @@ -2903,8 +2908,8 @@ struct _snd_pcm_runtime { - When the pcm supports the suspend/resume operation - (i.e. SNDRV_PCM_INFO_RESUME flag is set), + When the pcm supports the suspend/resume operation, + regardless of full or partial suspend/resume support, SUSPEND and RESUME 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 STOP and START commands, respectively. + See + Power Management section for details. @@ -5483,22 +5490,60 @@ struct _snd_pcm_runtime { CONFIG_PM. + + If the driver supports the suspend/resume + fully, that is, the device can be + properly resumed to the status at the suspend is called, + you can set SNDRV_PCM_INFO_RESUME 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 + SNDRV_PCM_TRIGGER_RESUME after resume + callback is finished. + + + + 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 + snd_pcm_prepare() and restart the stream + appropriately. Hence, you can define suspend/resume callbacks + below but don't set SNDRV_PCM_INFO_RESUME + info flag to the PCM. + + + + Note that the trigger with SUSPEND can be always called when + snd_pcm_suspend_all is called, + regardless of SNDRV_PCM_INFO_RESUME flag. + The RESUME flag affects only the behavior + of snd_pcm_resume(). + (Thus, in theory, + SNDRV_PCM_TRIGGER_RESUME isn't needed + to be handled in the trigger callback when no + SNDRV_PCM_INFO_RESUME flag is set. But, + it's better to keep it for compatibility reason.) + - 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: - Retrieve the chip data from pm_private_data field. + Retrieve the card and the chip data. + Call snd_power_change_state() with + SNDRV_CTL_POWER_D3hot to change the + power status. Call snd_pcm_suspend_all() to suspend the running PCM streams. + If AC97 codecs are used, call + snd_ac97_resume() for each codec. Save the register values if necessary. Stop the hardware if necessary. - Disable the PCI device by calling pci_disable_device(). + Disable the PCI device by calling + pci_disable_device(). Then, call + pci_save_state() at last. @@ -5525,18 +5577,24 @@ struct _snd_pcm_runtime { 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. - Retrieve the chip data from pm_private_data field. - Enable the pci device again by calling - pci_enable_device(). + Retrieve the card and the chip data. + Set up PCI. First, call pci_restore_state(). + Then enable the pci device again by calling pci_enable_device(). + Call pci_set_master() if necessary, too. Re-initialize the chip. Restore the saved registers if necessary. Resume the mixer, e.g. calling snd_ac97_resume(). Restart the hardware (if any). + Call snd_power_change_state() with + SNDRV_CTL_POWER_D0 to notify the processes. @@ -5565,12 +5626,15 @@ struct _snd_pcm_runtime { 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 { - 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 + snd_pcm_suspend_all() or + snd_pcm_suspend(). 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 SNDRV_PCM_TRIGGER_RESUME + when necessary. + + + + 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 + private_data field, in case you + created the chip data individually. + + + +private_data = chip; + .... + } +]]> + + + + When you created the chip data with + snd_card_new(), it's anyway accessible + via private_data field. @@ -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; .... } ]]> - 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. - 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. - 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. @@ -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 }; ]]> -- cgit v1.1