Re: [PATCH 1/6] drm/i915: Bring UP Power Wells before disabling RC6.

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

On 4/9/2014 9:43 AM, Ben Widawsky wrote:
> On Tue, Apr 08, 2014 at 06:22:52PM +0530, S, Deepak wrote:
>>
>>
>> On 4/8/2014 6:13 PM, Ville Syrjälä wrote:
>>> On Mon, Apr 07, 2014 at 02:36:20PM -0700, Ben Widawsky wrote:
>>>> On Mon, Apr 07, 2014 at 05:01:46PM -0300, Rodrigo Vivi wrote:
>>>>> From: Deepak S <deepak.s@intel.com>
>>>>>
>>>>> We need do forcewake before Disabling RC6, This is what the BIOS
>>>>> expects while going into suspend.
>>>>>
>>>>> v2: updated commit message. (Daniel)
>>>>>
>>>>> Signed-off-by: Deepak S <deepak.s@intel.com>
>>>>> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@gmail.com>
>>>>> ---
>>>>>   drivers/gpu/drm/i915/intel_pm.c | 6 ++++++
>>>>>   1 file changed, 6 insertions(+)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
>>>>> index 04af065..ad2ff99 100644
>>>>> --- a/drivers/gpu/drm/i915/intel_pm.c
>>>>> +++ b/drivers/gpu/drm/i915/intel_pm.c
>>>>> @@ -3198,8 +3198,14 @@ static void valleyview_disable_rps(struct drm_device *dev)
>>>>>   {
>>>>>   	struct drm_i915_private *dev_priv = dev->dev_private;
>>>>>
>>>>> +	/* we're doing forcewake before Disabling RC6,
>>>>> +	 * This what the BIOS expects when going into suspend */
>>>>> +	gen6_gt_force_wake_get(dev_priv, FORCEWAKE_ALL);
>>>>> +
>>>>>   	I915_WRITE(GEN6_RC_CONTROL, 0);
>>>>>
>>>>> +	gen6_gt_force_wake_put(dev_priv, FORCEWAKE_ALL);
>>>>> +
>>>>>   	gen6_disable_rps_interrupts(dev);
>>>>>   }
>>>>>
>>>>
>>>> Isn't the forcewake done as part of I915_WRITE sufficient?
>>>
>>> Writes don't do forcewake, nor is the register even part of the
>>> VLV forcewake ranges.
>>>
>>> I guess the rationale for this patche is still a bit vague. But if it's
>>> really needed, I wonder whether we should do this same dance for !VLV
>>> too? Do we have any "GPU stuck in wrong power state after suspend" type of
>>> bugs still around?
>>
>> One of suggestion form the HW team was to Bring the wells up before we
>> disable RC6 at run-time. We did see some issue when we enabled D0ix.
>>
>> I think the is a good practice to make sure we bring-up the wells before we
>> disable RC6. At least this avoids the cases where wells are not up before we
>> can access the Next register after disable.
>
> Ville was totally right. I do think a POSTING_READ is still sufficient.
> Don't care much either way.
>

If feel this patch is not adding any value. I OK dropping this patch.
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