Hi Jesse,
> -----Original Message-----
> From: Barnes, Jesse
> Sent: Friday, May 17, 2013 11:44 PM
> To: Wang Xingchao
> Cc: tiwai at suse.de; daniel at ffwll.ch; Girdwood, Liam R;
> david.henningsson at canonical.com; Lin, Mengdong; Li, Jocelyn;
> alsa-devel at alsa-project.org; intel-gfx at lists.freedesktop.org; Zanoni, Paulo R;
> Wang, Xingchao
> Subject: Re: [PATCH 1/2 V3] drm/915: Add private api for power well usage
>
> A few comments and questions below.
>
> On Thu, 16 May 2013 15:52:36 +0800
> Wang Xingchao <xingchao.wang at linux.intel.com> wrote:
>
> > Haswell Display audio depends on power well in graphic side, it should
> > request power well before use it and release power well after use.
> > I915 will not shutdown power well if it detects audio is using.
> > This patch protects display audio crash for Intel Haswell C3 stepping board.
> >
> > Signed-off-by: Wang Xingchao <xingchao.wang at linux.intel.com>
> > ---
> > drivers/gpu/drm/i915/intel_pm.c | 75
> +++++++++++++++++++++++++++++++++++----
> > include/drm/i915_powerwell.h | 36 +++++++++++++++++++
> > 2 files changed, 104 insertions(+), 7 deletions(-) create mode
> > 100644 include/drm/i915_powerwell.h
> >
> > diff --git a/drivers/gpu/drm/i915/intel_pm.c
> > b/drivers/gpu/drm/i915/intel_pm.c index 0f4b46e..88820e1 100644
> > --- a/drivers/gpu/drm/i915/intel_pm.c
> > +++ b/drivers/gpu/drm/i915/intel_pm.c
> > @@ -4344,18 +4344,12 @@ bool intel_using_power_well(struct drm_device
> *dev)
> > return true;
> > }
> >
> > -void intel_set_power_well(struct drm_device *dev, bool enable)
> > +static void enable_power_well(struct drm_device *dev, bool enable)
>
> We can leave the name of this function alone; even for static stuff we tend to
> use the intel_ prefix. Plus it's a set function, not an enable function... so
> maybe just put a __ in front of it to indicate it's for internal use only.
Changed in next version patch.
>
> > {
> > struct drm_i915_private *dev_priv = dev->dev_private;
> > bool is_enabled, enable_requested;
> > uint32_t tmp;
> >
>
>
> > +/* Global drm_device for display audio drvier usage */ static struct
> > +drm_device *power_well_device;
> > +/* Lock protecting power well setting */ static
> > +DEFINE_SPINLOCK(powerwell_lock); static bool i915_power_well_using;
>
> What does this mean? If it's just for making sure we don't use bogus
> power_well_device, it seems like we can just use a NULL check against
> power_well_device for that instead.
I915_power_well_using is used to track whether i915 module using power well.
If i915 module had "disable" request, audio driver would shut down power well at its release caller.
>
> > +static int hsw_power_count;
> > +
> > +void i915_request_power_well(void)
> > +{
> > + if (!power_well_device)
> > + return;
> > +
> > + if (!IS_HASWELL(power_well_device))
> > + return;
> > +
> > + spin_lock_irq(&powerwell_lock);
> > + if (!hsw_power_count++ && !i915_power_well_using)
> > + enable_power_well(power_well_device, true);
> > + spin_unlock_irq(&powerwell_lock);
> > +}
> > +EXPORT_SYMBOL_GPL(i915_request_power_well);
> > +
> > +void i915_release_power_well(void)
> > +{
> > + if (!power_well_device)
> > + return;
> > +
> > + if (!IS_HASWELL(power_well_device))
> > + return;
> > +
> > + spin_lock_irq(&powerwell_lock);
> > + WARN_ON(!hsw_power_count);
> > + if (!--hsw_power_count
> > + && !i915_power_well_using)
> > + enable_power_well(power_well_device, false);
> > + spin_unlock_irq(&powerwell_lock);
> > +}
> > +EXPORT_SYMBOL_GPL(i915_release_power_well);
> > +
> > +/* TODO: Call this when i915 module unload */ void
> > +i915_remove_power_well(void) {
> > + i915_power_well_using = false;
> > + power_well_device = NULL;
> > +}
> > +
> > +void intel_set_power_well(struct drm_device *dev, bool enable) {
> > + if (!HAS_POWER_WELL(dev))
> > + return;
> > +
> > + power_well_device = dev;
> > + spin_lock_irq(&powerwell_lock);
> > + i915_power_well_using = enable;
> > + if (!enable && hsw_power_count) {
> > + DRM_DEBUG_KMS("Display audio power well busy using now\n");
> > + goto out;
> > + }
> > +
> > + if (!i915_disable_power_well && !enable)
> > + goto out;
> > +
> > + enable_power_well(dev, enable);
> > +out:
> > + spin_unlock_irq(&powerwell_lock);
> > +}
>
> I think we should just set the power_well_device at module init time, then ou
> wouldn't need to check/set it here.
>
> Also, the existing i915 code could just use the request/release functions too
> (internal versions taking a drm_device *), then you wouldn't need this special
> case.
It's good that if i915 module could use such request/release function, then the power_count
could be used to track the both audio driver and i915 driver. I've reworked a new version patch
to let i915 use power_count too. But in fact it would introduce new issue: i915 may call intel_wet_power_well()
several times to enable power well, but only disable once. That makes conflicts to use the single power_count.
I'm thinking to solve it by:
- use different count number for i915 driver.
- filter useless enable request from i915.
I'm testing the new patchset and would send it out after everything works for me.
>
> > +/* For use by hda_i915 driver */
> > +extern void i915_request_power_well(void); extern void
> > +i915_release_power_well(void);
>
> For future proofing, it might be good if these took an enum for the power well
> being requested. Then we could track an array of refcounts later when we
> need the additional controls.
>
> But I suppose that could be added later when we have a better idea of what
> future chips will look like.
>
> Jesse
Thanks
--xingchao
