drm/i915: Fix runtime PM for LPE audio

commit 668e3b014afb66ab29e134bca7c258527273ac75 upstream.

Not calling pm_runtime_enable() means that runtime PM can't be
enabled at all via sysfs. So we definitely need to call it
from somewhere.

Calling it from the driver seems like a bad idea because it
would have to be paired with a pm_runtime_disable() at driver
unload time, otherwise the core gets upset. Also if there's
no LPE audio driver loaded then we couldn't runtime suspend
i915 either.

So it looks like a better plan is to call it from i915 when
we register the platform device. That seems to match how
pci generally does things. I cargo culted the
pm_runtime_forbid() and pm_runtime_set_active() calls from
pci as well.

The exposed runtime PM API is massive an thorougly misleading, so
I don't actually know if this is how you're supposed to use the API
or not. But it seems to work. I can now runtime suspend i915 again
with or without the LPE audio driver loaded, and reloading the
LPE audio driver also seems to work.

Note that powertop won't auto-tune runtime PM for platform devices,
which is a little annoying. So I'm not sure that leaving runtime
PM in "on" mode by default is the best choice here. But I've left
it like that for now at least.

Also remove the comment about there not being much benefit from
LPE audio runtime PM. Not allowing runtime PM blocks i915 runtime
PM, which will also block s0ix, and that could have a measurable
impact on power consumption.

Cc: Takashi Iwai <tiwai@suse.de>
Cc: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Fixes: 0b6b524f3915 ("ALSA: x86: Don't enable runtime PM as default")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170427160231.13337-2-ville.syrjala@linux.intel.com
Reviewed-by: Takashi Iwai <tiwai@suse.de>
(cherry picked from commit 183c00350ccda86781f6695840e6c5f5b22efbd1)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/gpu/drm/i915/intel_lpe_audio.c b/drivers/gpu/drm/i915/intel_lpe_audio.c
index 7a5b41b1c02414b293771080f701ae778c7380d7..999cb31ba63d792ef82304aa184b5a5c1299cb81 100644 (file)
--- a/drivers/gpu/drm/i915/intel_lpe_audio.c
+++ b/drivers/gpu/drm/i915/intel_lpe_audio.c
@@ -63,6 +63,7 @@
 #include <linux/acpi.h>
 #include <linux/device.h>
 #include <linux/pci.h>
+#include <linux/pm_runtime.h>
 
 #include "i915_drv.h"
 #include <linux/delay.h>
@@ -121,6 +122,10 @@ lpe_audio_platdev_create(struct drm_i915_private *dev_priv)
 
        kfree(rsc);
 
+       pm_runtime_forbid(&platdev->dev);
+       pm_runtime_set_active(&platdev->dev);
+       pm_runtime_enable(&platdev->dev);
+
        return platdev;
 
 err:

diff --git a/sound/x86/intel_hdmi_audio.c b/sound/x86/intel_hdmi_audio.c
index c505b019e09ce0795cc8ddd79cf1f8c6a18d32ff..bfac6f21ae5e183eaa9efec113cde1e8e5f4a833 100644 (file)
--- a/sound/x86/intel_hdmi_audio.c
+++ b/sound/x86/intel_hdmi_audio.c
@@ -1809,10 +1809,6 @@ static int hdmi_lpe_audio_probe(struct platform_device *pdev)
        pdata->notify_pending = false;
        spin_unlock_irq(&pdata->lpe_audio_slock);
 
-       /* runtime PM isn't enabled as default, since it won't save much on
-        * BYT/CHT devices; user who want the runtime PM should adjust the
-        * power/ontrol and power/autosuspend_delay_ms sysfs entries instead
-        */
        pm_runtime_use_autosuspend(&pdev->dev);
        pm_runtime_mark_last_busy(&pdev->dev);
        pm_runtime_set_active(&pdev->dev);