Re: [alsa-devel] [PATCH 1/4 V5] i915/drm: Add private api for power well usage

At Thu, 23 May 2013 01:04:13 +0800, Wang Xingchao 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@linux.intel.com

Just minor points:

+/* Display audio driver power well request */ +void i915_request_power_well(void) +{

• if (hsw_pwr == NULL)

• return;
  

• spin_lock_irq(&hsw_pwr->lock);

If both functions are supposed to be called only in non-sleepable state, there is no merit to use _irq version of spinlock. OTOH, if this function can be called from non-sleepable context, spin_lock_irq() is wrong.

That is, the lock here should be either spin_lock() (supposing all places are not from interrupt context) or spin_lock_irqsave() (allowing from interrupt context).

• if (!hsw_pwr->count++ &&

• 	!hsw_pwr->i915_request)
  

• __intel_set_power_well(hsw_pwr->device, true);
  

• spin_unlock_irq(&hsw_pwr->lock);

+} +EXPORT_SYMBOL_GPL(i915_request_power_well);

+/* Display audio driver power well release */ +void i915_release_power_well(void) +{

• if (hsw_pwr == NULL)

• return;
  

• spin_lock_irq(&hsw_pwr->lock);
• WARN_ON(!hsw_pwr->count);
• if (!--hsw_pwr->count &&

•        !hsw_pwr->i915_request)
  

• __intel_set_power_well(hsw_pwr->device, false);
  

• spin_unlock_irq(&hsw_pwr->lock);

+} +EXPORT_SYMBOL_GPL(i915_release_power_well);

+int i915_init_power_well(struct drm_device *dev) +{

• struct drm_i915_private *dev_priv = dev->dev_private;

Since this is a global variable that must be initialized only once, safer to have WARN_ON(hsw_pwr);

• hsw_pwr = kzalloc(sizeof *hsw_pwr, GFP_KERNEL);
• if (hsw_pwr == NULL)

• return -ENOMEM;
  

• dev_priv->hsw_pwr = hsw_pwr;
• hsw_pwr->device = dev;
• spin_lock_init(&hsw_pwr->lock);
• hsw_pwr->count = 0;
• return 0;

+}

+void i915_remove_power_well(struct drm_device *dev) +{

• struct drm_i915_private *dev_priv = dev->dev_private;

... and WARN_ON(hsw_ptr != dev_priv->hsw_pwr);

• kfree(dev_priv->hsw_pwr);
• dev_priv->hsw_pwr = NULL;
• hsw_pwr = NULL;

+}

Takashi

+void intel_set_power_well(struct drm_device *dev, bool enable) +{

• struct drm_i915_private *dev_priv = dev->dev_private;
• struct i915_power_well *power_well = dev_priv->hsw_pwr;
• if (!HAS_POWER_WELL(dev))

• return;
  

• if (!i915_disable_power_well && !enable)

• return;
  

• if (!power_well)

• return;
  

• spin_lock_irq(&power_well->lock);
• power_well->i915_request = enable;
• /* only reject "disable" power well request */
• if (power_well->count && !enable) {

• spin_unlock_irq(&power_well->lock);
  

• return;
  

• }
• __intel_set_power_well(dev, enable);
• spin_unlock_irq(&power_well->lock);

+}

/*

• Starting with Haswell, we have a "Power Down Well" that can be turned off
• when not needed anymore. We have 4 registers that can request the power well

diff --git a/include/drm/i915_powerwell.h b/include/drm/i915_powerwell.h new file mode 100644 index 0000000..cfdc884 --- /dev/null +++ b/include/drm/i915_powerwell.h @@ -0,0 +1,36 @@ +/**************************************************************************

• • Copyright 2013 Intel Inc.
• • All Rights Reserved.
• • Permission is hereby granted, free of charge, to any person obtaining a
• • copy of this software and associated documentation files (the
• • "Software"), to deal in the Software without restriction, including
• • without limitation the rights to use, copy, modify, merge, publish,
• • distribute, sub license, and/or sell copies of the Software, and to
• • permit persons to whom the Software is furnished to do so, subject to
• • the following conditions:
• • The above copyright notice and this permission notice (including the
• • next paragraph) shall be included in all copies or substantial portions
• • of the Software.
• • THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
• • IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
• • FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
• • THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
• • DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
• • OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
• • USE OR OTHER DEALINGS IN THE SOFTWARE.
• **************************************************************************/

+#ifndef _I915_POWERWELL_H_ +#define _I915_POWERWELL_H_

+/* For use by hda_i915 driver */ +extern void i915_request_power_well(void); +extern void i915_release_power_well(void);

+#endif /* _I915_POWERWELL_H_ */

1.8.1.2