Re: [PATCH 14/15] drm/i915: vlv: add runtime PM support

[Daniel Vetter <daniel@ffwll.ch>]

On Wed, Apr 09, 2014 at 06:43:10PM +0300, Imre Deak wrote:
> On Wed, 2014-04-09 at 16:22 +0200, Daniel Vetter wrote:
> > On Tue, Apr 08, 2014 at 07:57:55PM +0300, Imre Deak wrote:
> > > Add runtime PM support for VLV, but leave it disabled. The next patch
> > > enables it.
> > > 
> > > The suspend/resume sequence used is based on [1] and [2]. In practice we
> > > depend on the GT RC6 mechanism to save the HW context depending on the
> > > render and media power wells. By the time we run the runtime suspend
> > > callback the display side is also off and the HW context for that is
> > > managed by the display power domain framework.
> > > 
> > > Besides the above there are Gunit registers that depend on a system-wide
> > > power well. This power well goes off once the device enters any of the
> > > S0i[R123] states. To handle this scenario, save/restore these Gunit
> > > registers. Note that this is not the complete register set dictated by
> > > [2], to remove some overhead registers that are known not to be used are
> > > ignored. Also some registers are fully setup by initialization functions
> > > called during resume, these are not saved either. The list of registers
> > > can be further reduced, see the TODO note in the code.
> > > 
> > > [1] VLV_gfx_clocking_PM_reset_y12w21d3 / "Driver D3 entry/exit"
> > > [2] VLV2_S0IXRegs
> > > 
> > > Signed-off-by: Imre Deak <imre.deak@intel.com>
> > > ---
> > >  drivers/gpu/drm/i915/i915_drv.c | 170 +++++++++++++++++++++++++++++++++++++++-
> > >  1 file changed, 166 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/drivers/gpu/drm/i915/i915_drv.c b/drivers/gpu/drm/i915/i915_drv.c
> > > index 9f9d0db..16ca37f 100644
> > > --- a/drivers/gpu/drm/i915/i915_drv.c
> > > +++ b/drivers/gpu/drm/i915/i915_drv.c
> > > @@ -891,19 +891,23 @@ static int i915_pm_poweroff(struct device *dev)
> > >  	return i915_drm_freeze(drm_dev);
> > >  }
> > >  
> > > -static void snb_runtime_suspend(struct drm_i915_private *dev_priv)
> > > +static int snb_runtime_suspend(struct drm_i915_private *dev_priv)
> > >  {
> > >  	struct drm_device *dev = dev_priv->dev;
> > >  
> > >  	intel_runtime_pm_disable_interrupts(dev);
> > > +
> > > +	return 0;
> > >  }
> > >  
> > > -static void hsw_runtime_suspend(struct drm_i915_private *dev_priv)
> > > +static int hsw_runtime_suspend(struct drm_i915_private *dev_priv)
> > >  {
> > >  	hsw_enable_pc8(dev_priv);
> > > +
> > > +	return 0;
> > >  }
> > >  
> > > -static void snb_runtime_resume(struct drm_i915_private *dev_priv)
> > > +static int snb_runtime_resume(struct drm_i915_private *dev_priv)
> > >  {
> > >  	struct drm_device *dev = dev_priv->dev;
> > >  
> > > @@ -913,11 +917,15 @@ static void snb_runtime_resume(struct drm_i915_private *dev_priv)
> > >  	mutex_lock(&dev_priv->rps.hw_lock);
> > >  	gen6_update_ring_freq(dev);
> > >  	mutex_unlock(&dev_priv->rps.hw_lock);
> > > +
> > > +	return 0;
> > >  }
> > >  
> > > -static void hsw_runtime_resume(struct drm_i915_private *dev_priv)
> > > +static int hsw_runtime_resume(struct drm_i915_private *dev_priv)
> > >  {
> > >  	hsw_disable_pc8(dev_priv);
> > > +
> > > +	return 0;
> > >  }
> > >  
> > >  /*
> > > @@ -1144,11 +1152,155 @@ int vlv_force_gfx_clock(struct drm_i915_private *dev_priv, bool force_on)
> > >  #undef COND
> > >  }
> > >  
> > > +static int vlv_allow_gt_wake(struct drm_i915_private *dev_priv, bool allow)
> > > +{
> > > +	u32 val;
> > > +	int err = 0;
> > > +
> > > +	val = I915_READ(VLV_GTLC_WAKE_CTRL);
> > > +	val &= ~VLV_GTLC_ALLOWWAKEREQ;
> > > +	if (allow)
> > > +		val |= VLV_GTLC_ALLOWWAKEREQ;
> > > +	I915_WRITE(VLV_GTLC_WAKE_CTRL, val);
> > > +	POSTING_READ(VLV_GTLC_WAKE_CTRL);
> > > +
> > > +#define COND (!!(I915_READ(VLV_GTLC_PW_STATUS) & VLV_GTLC_ALLOWWAKEACK) == \
> > > +	      allow)
> > > +	err = wait_for(COND, 1);
> > > +	if (err)
> > > +		DRM_ERROR("timeout disabling GT waking\n");
> > > +	return err;
> > > +#undef COND
> > > +}
> > > +
> > > +static int vlv_wait_for_gt_wells(struct drm_i915_private *dev_priv,
> > > +				 bool wait_for_on)
> > > +{
> > > +	u32 mask;
> > > +	u32 val;
> > > +	int err;
> > > +
> > > +	mask = VLV_GTLC_PW_MEDIA_STATUS_MASK | VLV_GTLC_PW_RENDER_STATUS_MASK;
> > > +	val = wait_for_on ? mask : 0;
> > > +#define COND ((I915_READ(VLV_GTLC_PW_STATUS) & mask) == val)
> > > +	if (COND)
> > > +		return 0;
> > > +
> > > +	DRM_DEBUG_KMS("waiting for GT wells to go %s (%08x)\n",
> > > +			wait_for_on ? "on" : "off",
> > > +			I915_READ(VLV_GTLC_PW_STATUS));
> > > +
> > > +	/*
> > > +	 * RC6 transitioning can be delayed up to 2 msec (see
> > > +	 * valleyview_enable_rps), use 3 msec for safety.
> > > +	 */
> > > +	err = wait_for(COND, 3);
> > > +	if (err)
> > > +		DRM_ERROR("timeout waiting for GT wells to go %s\n",
> > > +			  wait_for_on ? "on" : "off");
> > > +
> > > +	return err;
> > > +#undef COND
> > > +}
> > > +
> > > +static void vlv_check_no_gt_access(struct drm_i915_private *dev_priv)
> > > +{
> > > +	if (!(I915_READ(VLV_GTLC_PW_STATUS) & VLV_GTLC_ALLOWWAKEERR))
> > > +		return;
> > > +
> > > +	DRM_ERROR("GT register access while GT waking disabled\n");
> > > +	I915_WRITE(VLV_GTLC_PW_STATUS, VLV_GTLC_ALLOWWAKEERR);
> > > +}
> > > +
> > > +static int vlv_runtime_suspend(struct drm_i915_private *dev_priv)
> > > +{
> > > +	struct drm_device *dev = dev_priv->dev;
> > > +	u32 mask;
> > > +	int err;
> > > +
> > > +	if (WARN_ON(!valleyview_rc6_enabled(dev)))
> > > +		return -ENODEV;
> > > +
> > > +	intel_runtime_pm_disable_interrupts(dev);
> > > +	cancel_work_sync(&dev_priv->rps.work);
> > > +
> > > +	/*
> > > +	 * Bspec defines the following GT well on flags as debug only, so
> > > +	 * don't treat them as hard failures.
> > > +	 */
> > > +	(void)vlv_wait_for_gt_wells(dev_priv, false);
> > > +
> > > +	mask = VLV_GTLC_RENDER_CTX_EXISTS | VLV_GTLC_MEDIA_CTX_EXISTS;
> > > +	WARN_ON((I915_READ(VLV_GTLC_WAKE_CTRL) & mask) != mask);
> > > +
> > > +	vlv_check_no_gt_access(dev_priv);
> > > +
> > > +	err = vlv_force_gfx_clock(dev_priv, true);
> > > +	if (err)
> > > +		goto err1;
> > > +
> > > +	err = vlv_allow_gt_wake(dev_priv, false);
> > > +	if (err)
> > > +		goto err2;
> > > +	vlv_save_gunit_s0ix_state(dev_priv);
> > > +
> > > +	err = vlv_force_gfx_clock(dev_priv, false);
> > > +	if (err)
> > > +		goto err2;
> > > +
> > > +	return 0;
> > > +
> > > +err2:
> > > +	/* For safety always re-enable waking and disable gfx clock forcing */
> > > +	vlv_allow_gt_wake(dev_priv, true);
> > > +err1:
> > > +	vlv_force_gfx_clock(dev_priv, false);
> > > +	intel_runtime_pm_restore_interrupts(dev);
> > > +
> > > +	return err;
> > > +}
> > > +
> > > +static int vlv_runtime_resume(struct drm_i915_private *dev_priv)
> > > +{
> > > +	struct drm_device *dev = dev_priv->dev;
> > > +	int err;
> > > +	int ret;
> > > +
> > > +	/*
> > > +	 * If any of the steps fail just try to continue, that's the best we
> > > +	 * can do at this point. Return the first error code (which will also
> > > +	 * leave RPM permanentyl disabled).
> > > +	 */
> > > +	ret = vlv_force_gfx_clock(dev_priv, true);
> > > +
> > > +	vlv_restore_gunit_s0ix_state(dev_priv);
> > > +
> > > +	err = vlv_allow_gt_wake(dev_priv, true);
> > > +	if (!ret)
> > > +		ret = err;
> > > +
> > > +	err = vlv_force_gfx_clock(dev_priv, false);
> > > +	if (!ret)
> > > +		ret = err;
> > > +
> > > +	vlv_check_no_gt_access(dev_priv);
> > > +
> > > +	intel_init_clock_gating(dev);
> > > +	intel_reset_gt_powersave(dev);
> > > +	i915_gem_init_swizzling(dev);
> > > +	i915_gem_restore_fences(dev);
> > > +
> > > +	intel_runtime_pm_restore_interrupts(dev);
> > > +
> > > +	return ret;
> > > +}
> > > +
> > >  static int intel_runtime_suspend(struct device *device)
> > >  {
> > >  	struct pci_dev *pdev = to_pci_dev(device);
> > >  	struct drm_device *dev = pci_get_drvdata(pdev);
> > >  	struct drm_i915_private *dev_priv = dev->dev_private;
> > > +	int ret = 0;
> > >  
> > >  	if (WARN_ON_ONCE(!dev_priv->rps.enabled))
> > >  		return -ENODEV;
> > > @@ -1162,9 +1314,17 @@ static int intel_runtime_suspend(struct device *device)
> > >  		snb_runtime_suspend(dev_priv);
> > >  	else if (IS_HASWELL(dev) || IS_BROADWELL(dev))
> > >  		hsw_runtime_suspend(dev_priv);
> > > +	else if (IS_VALLEYVIEW(dev))
> > > +		ret = vlv_runtime_suspend(dev_priv);
> > >  	else
> > >  		WARN_ON(1);
> > >  
> > > +	if (ret) {
> > > +		DRM_ERROR("Runtime suspend failed, disabling it\n");
> > > +
> > > +		return ret;
> > > +	}
> > > +
> > >  	i915_gem_release_all_mmaps(dev_priv);
> > >  
> > >  	del_timer_sync(&dev_priv->gpu_error.hangcheck_timer);
> > > @@ -1200,6 +1360,8 @@ static int intel_runtime_resume(struct device *device)
> > >  		snb_runtime_resume(dev_priv);
> > >  	else if (IS_HASWELL(dev) || IS_BROADWELL(dev))
> > >  		hsw_runtime_resume(dev_priv);
> > > +	else if (IS_VALLEYVIEW(dev))
> > > +		vlv_runtime_resume(dev_priv);
> > 
> > Golden rule of refactoring: The 3rd guy gets to cleanup the mess. Imo
> > it's time to refactor the common parts form these platform functions out
> > and move them into generic code, and only call down into platform code as
> > needed. If we don't do that we'll have completely hell due to slight
> > differences in ordering between platforms.
> 
> Ok, the common parts basically boil down to
> 
> intel_runtime_pm_disable_interrupts(); / _enable_interrupts();
> 
> and I think we also need to add
> 
> cancel_work_sync(&dev_priv->rps.work);
> 
> to all platforms. I can do this.
> 
> > Also I think we should try to share as much code as possible with the
> > other setup/teardowns paths, i.e. driver load/unload, system
> > suspend/resume and gpu reset.
> 
> I agree, but this needs much more refactoring first on the other parts
> you mention above before we can unify things. That's mainly because on
> the RPM path we can call only low level functions (since an RPM callback
> can be called basically from anywhere in the driver) whereas the
> handlers you mention do a high level initialization. So for VLV RPM
> resume we call for example 
> 
> intel_init_clock_gating();
> i915_gem_init_swizzling();
> i915_gem_restore_fences();
> 
> but for system resume we simply do a full
> 
> intel_modeset_init_hw();
> 
> which includes the above low level steps interleaved with quite a lot of
> other init steps. We may also need to rethink locking before sharing
> those parts.  
> 
> So I'm happy to do this refactoring, but I'd suggest doing it as a
> follow-up.

Yeah I agree that the full thing needs more work and maybe 1-2 more
platforms so that we have a clearer picture. But imo it's time to start,
and the above few things you've mentioned look like a good first stab at
the problem.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch