Re: [PATCH v4 2/2] drm/i915/vlv: WA to fix Voltage not getting dropped to Vmin when Gfx is power gated.

["S, Deepak" <deepak.s@intel.com>]

On 1/27/2014 10:22 PM, Daniel Vetter wrote:
> On Mon, Jan 27, 2014 at 09:35:06PM +0530, deepak.s@intel.com wrote:
>> From: Deepak S <deepak.s@intel.com>
>>
>> When we enter RC6 and GFX Clocks are off, the voltage remains higher
>> than Vmin. When we try to set the freq to RPn, it might fail since the
>> Gfx clocks are down. So to fix this in Gfx idle, Bring the GFX clock up
>> and set the freq to RPn then move GFx down.
>>
>> v2: remove vlv_update_rps_cur_delay function. Update commit message (Daniel)
>>
>> v3: Fix the timeout during wait for gfx clock (Jesse)
>>
>> v4: addressed comments on set freq and punit wait (Ville)
>>
>> Signed-off-by: Deepak S <deepak.s@intel.com>
>> ---
>>   drivers/gpu/drm/i915/i915_reg.h |  4 ++++
>>   drivers/gpu/drm/i915/intel_pm.c | 53 ++++++++++++++++++++++++++++++++++++++++-
>>   2 files changed, 56 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
>> index 242f540..feaa83b 100644
>> --- a/drivers/gpu/drm/i915/i915_reg.h
>> +++ b/drivers/gpu/drm/i915/i915_reg.h
>> @@ -4944,6 +4944,10 @@
>>   						 GEN6_PM_RP_DOWN_THRESHOLD | \
>>   						 GEN6_PM_RP_DOWN_TIMEOUT)
>>
>> +#define VLV_GTLC_SURVIVABILITY_REG              0x130098
>> +#define VLV_GFX_CLK_STATUS_BIT			(1<<3)
>> +#define VLV_GFX_CLK_FORCE_ON_BIT		(1<<2)
>> +
>>   #define GEN6_GT_GFX_RC6_LOCKED			0x138104
>>   #define VLV_COUNTER_CONTROL			0x138104
>>   #define   VLV_COUNT_RANGE_HIGH			(1<<15)
>> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
>> index c6a07c9..84e20d0 100644
>> --- a/drivers/gpu/drm/i915/intel_pm.c
>> +++ b/drivers/gpu/drm/i915/intel_pm.c
>> @@ -3035,6 +3035,56 @@ void gen6_set_rps(struct drm_device *dev, u8 val)
>>   	trace_intel_gpu_freq_change(val * 50);
>>   }
>>
>> +/* vlv_set_rps_idle: Set the frequency to Rpn if Gfx clocks are down
>> + *
>> + * * If Gfx is Idle, then
>> + * 1. Mask Turbo interrupts
>> + * 2. Bring up Gfx clock
>> + * 3. Change the freq to Rpn and wait till P-Unit updates freq
>> + * 4. Clear the Force GFX CLK ON bit so that Gfx can down
>> + * 5. Unmask Turbo interrupts
>> +*/
>> +static void vlv_set_rps_idle(struct drm_i915_private *dev_priv)
>> +{
>> +	/*
>> +	 * When we are idle.  Drop to min voltage state.
>> +	 */
>> +
>> +	if (dev_priv->rps.cur_delay <= dev_priv->rps.min_delay)
>> +		return;
>> +
>> +	/* Mask turbo interrupt so that they will not come in between */
>> +	I915_WRITE(GEN6_PMINTRMSK, 0xffffffff);
>> +
>> +	/* Bring up the Gfx clock */
>> +	I915_WRITE(VLV_GTLC_SURVIVABILITY_REG,
>> +		I915_READ(VLV_GTLC_SURVIVABILITY_REG) |
>> +				VLV_GFX_CLK_FORCE_ON_BIT);
>> +
>> +	if (wait_for_atomic(((VLV_GFX_CLK_STATUS_BIT &
>
> Do we really need an atomic register busy loop here? Afaics this is only
> called from process context, so the normal wait_for macro should be good
> enough ...
> -Daniel
I agree, the reason why i did the _atomic as we observed delay in 
scheduling the wait_for and we ended up spending lot of time here.
I will wait for other comments, If i dont get any, I will address this 
comment and submit the patch.

>> +		I915_READ(VLV_GTLC_SURVIVABILITY_REG)) != 0), 5)) {
>> +			DRM_ERROR("GFX_CLK_ON request timed out\n");
>> +		return;
>> +	}
>> +
>> +	vlv_punit_write(dev_priv, PUNIT_REG_GPU_FREQ_REQ, dev_priv->rps.min_delay);
>> +
>> +	if (wait_for_atomic(((vlv_punit_read(dev_priv, PUNIT_REG_GPU_FREQ_STS))
>> +				& GENFREQSTATUS) == 0, 5))
>> +		DRM_DEBUG_DRIVER("timed out waiting for Punit\n");
>> +
>> +	/* Release the Gfx clock */
>> +	I915_WRITE(VLV_GTLC_SURVIVABILITY_REG,
>> +		I915_READ(VLV_GTLC_SURVIVABILITY_REG) &
>> +				~VLV_GFX_CLK_FORCE_ON_BIT);
>> +
>> +	/* Unmask Turbo interrupts */
>> +	I915_WRITE(GEN6_PMINTRMSK, ~(GEN6_PM_RPS_EVENTS |
>> +					GEN6_PM_RP_UP_EI_EXPIRED));
>> +}
>> +
>> +
>> +
>>   void gen6_rps_idle(struct drm_i915_private *dev_priv)
>>   {
>>   	struct drm_device *dev = dev_priv->dev;
>> @@ -3042,7 +3092,7 @@ void gen6_rps_idle(struct drm_i915_private *dev_priv)
>>   	mutex_lock(&dev_priv->rps.hw_lock);
>>   	if (dev_priv->rps.enabled) {
>>   		if (IS_VALLEYVIEW(dev))
>> -			valleyview_set_rps(dev_priv->dev, dev_priv->rps.min_delay);
>> +			vlv_set_rps_idle(dev_priv);
>>   		else
>>   			gen6_set_rps(dev_priv->dev, dev_priv->rps.min_delay);
>>   		dev_priv->rps.last_adj = 0;
>> @@ -4273,6 +4323,7 @@ void intel_gpu_ips_teardown(void)
>>   	i915_mch_dev = NULL;
>>   	spin_unlock_irq(&mchdev_lock);
>>   }
>> +
>>   static void intel_init_emon(struct drm_device *dev)
>>   {
>>   	struct drm_i915_private *dev_priv = dev->dev_private;
>> --
>> 1.8.5.2
>>
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>