Lukas Wunner
2016-Nov-08 11:57 UTC
[Nouveau] [PATCH] drm/nouveau: Drop superfluous DRM_SWITCH_POWER_DYNAMIC_OFF checks
nouveau's ->suspend and ->resume callbacks are currently skipped if the device's status is either DRM_SWITCH_POWER_OFF (powered off by vga_switcheroo manual power control) or DRM_SWITCH_POWER_DYNAMIC_OFF (runtime suspended). In the former case this makes sense since the device is powered off behind the PM core's back: It will try to execute the ->suspend and ->resume callbacks upon system sleep, not knowing that the device is inaccessible. Therefore the callbacks have to become no-ops. However the latter case doesn't make any sense because the PM core never calls the ->suspend and ->resume callbacks of runtime suspended devices: Such devices are either runtime resumed before going to system sleep (see call to pm_runtime_resume() in drivers/pci/pci-driver: pci_pm_suspend()) or they are left runtime suspended over the entire system suspend/resume process (search for "direct_complete" in drivers/base/power/main.c). Consequently the DRM_SWITCH_POWER_DYNAMIC_OFF checks are superfluous. Drop them. Signed-off-by: Lukas Wunner <lukas at wunner.de> --- drivers/gpu/drm/nouveau/nouveau_drm.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c index 9876e6f..d91d092 100644 --- a/drivers/gpu/drm/nouveau/nouveau_drm.c +++ b/drivers/gpu/drm/nouveau/nouveau_drm.c @@ -666,8 +666,7 @@ static int nouveau_drm_probe(struct pci_dev *pdev, struct drm_device *drm_dev = pci_get_drvdata(pdev); int ret; - if (drm_dev->switch_power_state == DRM_SWITCH_POWER_OFF || - drm_dev->switch_power_state == DRM_SWITCH_POWER_DYNAMIC_OFF) + if (drm_dev->switch_power_state == DRM_SWITCH_POWER_OFF) return 0; ret = nouveau_do_suspend(drm_dev, false); @@ -688,8 +687,7 @@ static int nouveau_drm_probe(struct pci_dev *pdev, struct drm_device *drm_dev = pci_get_drvdata(pdev); int ret; - if (drm_dev->switch_power_state == DRM_SWITCH_POWER_OFF || - drm_dev->switch_power_state == DRM_SWITCH_POWER_DYNAMIC_OFF) + if (drm_dev->switch_power_state == DRM_SWITCH_POWER_OFF) return 0; pci_set_power_state(pdev, PCI_D0); -- 2.10.1
Peter Wu
2016-Nov-08 20:29 UTC
[Nouveau] [PATCH] drm/nouveau: Drop superfluous DRM_SWITCH_POWER_DYNAMIC_OFF checks
On Tue, Nov 08, 2016 at 12:57:00PM +0100, Lukas Wunner wrote:> nouveau's ->suspend and ->resume callbacks are currently skipped if the > device's status is either DRM_SWITCH_POWER_OFF (powered off by > vga_switcheroo manual power control) or DRM_SWITCH_POWER_DYNAMIC_OFF > (runtime suspended). > > In the former case this makes sense since the device is powered off > behind the PM core's back: It will try to execute the ->suspend and > ->resume callbacks upon system sleep, not knowing that the device is > inaccessible. Therefore the callbacks have to become no-ops. > > However the latter case doesn't make any sense because the PM core > never calls the ->suspend and ->resume callbacks of runtime suspended > devices: Such devices are either runtime resumed before going to system > sleep (see call to pm_runtime_resume() in drivers/pci/pci-driver: > pci_pm_suspend()) or they are left runtime suspended over the entire > system suspend/resume process (search for "direct_complete" in > drivers/base/power/main.c). > > Consequently the DRM_SWITCH_POWER_DYNAMIC_OFF checks are superfluous. > Drop them. > > Signed-off-by: Lukas Wunner <lukas at wunner.de>It is better to rely on the official documentation rather than the implementation. Luckily, Documentation/power/pci.txt supports the claim: 2.4.1. System Suspend When the system is going into a sleep state in which the contents of memory will be preserved, such as one of the ACPI sleep states S1-S3, the phases are: prepare, suspend, suspend_noirq. [..] The pci_pm_prepare() routine first puts the device into the "fully functional" state with the help of pm_runtime_resume(). [..] So indeed we can be sure that the device is runtime-resumed before suspend. System resume is not documented explicitly, but it seems reasonable that the device is not runtime-suspended between system suspend and resume. Reviewed-by: Peter Wu <peter at lekensteyn.nl>> --- > drivers/gpu/drm/nouveau/nouveau_drm.c | 6 ++---- > 1 file changed, 2 insertions(+), 4 deletions(-) > > diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c > index 9876e6f..d91d092 100644 > --- a/drivers/gpu/drm/nouveau/nouveau_drm.c > +++ b/drivers/gpu/drm/nouveau/nouveau_drm.c > @@ -666,8 +666,7 @@ static int nouveau_drm_probe(struct pci_dev *pdev, > struct drm_device *drm_dev = pci_get_drvdata(pdev); > int ret; > > - if (drm_dev->switch_power_state == DRM_SWITCH_POWER_OFF || > - drm_dev->switch_power_state == DRM_SWITCH_POWER_DYNAMIC_OFF) > + if (drm_dev->switch_power_state == DRM_SWITCH_POWER_OFF) > return 0; > > ret = nouveau_do_suspend(drm_dev, false); > @@ -688,8 +687,7 @@ static int nouveau_drm_probe(struct pci_dev *pdev, > struct drm_device *drm_dev = pci_get_drvdata(pdev); > int ret; > > - if (drm_dev->switch_power_state == DRM_SWITCH_POWER_OFF || > - drm_dev->switch_power_state == DRM_SWITCH_POWER_DYNAMIC_OFF) > + if (drm_dev->switch_power_state == DRM_SWITCH_POWER_OFF) > return 0; > > pci_set_power_state(pdev, PCI_D0); > -- > 2.10.1
Lukas Wunner
2016-Dec-14 19:00 UTC
[Nouveau] [PATCH] drm/nouveau: Drop superfluous DRM_SWITCH_POWER_DYNAMIC_OFF checks
Hi Ben, On Tue, Nov 08, 2016 at 09:29:38PM +0100, Peter Wu wrote:> On Tue, Nov 08, 2016 at 12:57:00PM +0100, Lukas Wunner wrote: > > nouveau's ->suspend and ->resume callbacks are currently skipped if the > > device's status is either DRM_SWITCH_POWER_OFF (powered off by > > vga_switcheroo manual power control) or DRM_SWITCH_POWER_DYNAMIC_OFF > > (runtime suspended). > > > > In the former case this makes sense since the device is powered off > > behind the PM core's back: It will try to execute the ->suspend and > > ->resume callbacks upon system sleep, not knowing that the device is > > inaccessible. Therefore the callbacks have to become no-ops. > > > > However the latter case doesn't make any sense because the PM core > > never calls the ->suspend and ->resume callbacks of runtime suspended > > devices: Such devices are either runtime resumed before going to system > > sleep (see call to pm_runtime_resume() in drivers/pci/pci-driver: > > pci_pm_suspend()) or they are left runtime suspended over the entire > > system suspend/resume process (search for "direct_complete" in > > drivers/base/power/main.c). > > > > Consequently the DRM_SWITCH_POWER_DYNAMIC_OFF checks are superfluous. > > Drop them. > > > > Signed-off-by: Lukas Wunner <lukas at wunner.de>Just a gentle ping: This patch was posted a month ago and I'm not seeing it in your tree. Do you have objections? Should I repost with Peter's Reviewed-by? Thanks, Lukas> > It is better to rely on the official documentation rather than the > implementation. Luckily, Documentation/power/pci.txt supports the claim: > > 2.4.1. System Suspend > > When the system is going into a sleep state in which the contents of memory will > be preserved, such as one of the ACPI sleep states S1-S3, the phases are: > > prepare, suspend, suspend_noirq. > [..] > The pci_pm_prepare() routine first puts the device into the "fully functional" > state with the help of pm_runtime_resume(). [..] > > So indeed we can be sure that the device is runtime-resumed before > suspend. System resume is not documented explicitly, but it seems > reasonable that the device is not runtime-suspended between system > suspend and resume. > > Reviewed-by: Peter Wu <peter at lekensteyn.nl> > > > --- > > drivers/gpu/drm/nouveau/nouveau_drm.c | 6 ++---- > > 1 file changed, 2 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/gpu/drm/nouveau/nouveau_drm.c b/drivers/gpu/drm/nouveau/nouveau_drm.c > > index 9876e6f..d91d092 100644 > > --- a/drivers/gpu/drm/nouveau/nouveau_drm.c > > +++ b/drivers/gpu/drm/nouveau/nouveau_drm.c > > @@ -666,8 +666,7 @@ static int nouveau_drm_probe(struct pci_dev *pdev, > > struct drm_device *drm_dev = pci_get_drvdata(pdev); > > int ret; > > > > - if (drm_dev->switch_power_state == DRM_SWITCH_POWER_OFF || > > - drm_dev->switch_power_state == DRM_SWITCH_POWER_DYNAMIC_OFF) > > + if (drm_dev->switch_power_state == DRM_SWITCH_POWER_OFF) > > return 0; > > > > ret = nouveau_do_suspend(drm_dev, false); > > @@ -688,8 +687,7 @@ static int nouveau_drm_probe(struct pci_dev *pdev, > > struct drm_device *drm_dev = pci_get_drvdata(pdev); > > int ret; > > > > - if (drm_dev->switch_power_state == DRM_SWITCH_POWER_OFF || > > - drm_dev->switch_power_state == DRM_SWITCH_POWER_DYNAMIC_OFF) > > + if (drm_dev->switch_power_state == DRM_SWITCH_POWER_OFF) > > return 0; > > > > pci_set_power_state(pdev, PCI_D0); > > -- > > 2.10.1
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