Re: [PATCH 5/8] drm/i915: Optimize HDCP key load

[Ramalingam C <ramalingam.c@intel.com>]

On Friday 02 February 2018 07:48 PM, Sean Paul wrote:
> On Fri, Feb 02, 2018 at 04:15:17PM +0530, Ramalingam C wrote:
>> HDCP key need not be cleared on each hdcp disable. And HDCP key Load
>> is skipped if key is already loaded.
>>
> I had previously encountered issues without clearing the key in my testing.
> IIRC, without clearing the keys things acted differently. How much time are we
> saving by optimizing this?
>
> Sean
Time profiling is not done. As per the Bspec, Once Keys are loaded, they 
will be cleared only when PG1/PG0 is off.
So on Resume we need to load the keys. Since we have the status register 
for key load state, I feel we could rely on them.

Now with our code state, I am not seeing the need for reloading the 
keys. I have tested on KBL.
I think this is worth an attempt as no failures are observed.

--Ram
>
>
>> Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
>> ---
>>   drivers/gpu/drm/i915/intel_hdcp.c | 6 ++++--
>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_hdcp.c b/drivers/gpu/drm/i915/intel_hdcp.c
>> index fa2e7c727d00..5de9afd275b2 100644
>> --- a/drivers/gpu/drm/i915/intel_hdcp.c
>> +++ b/drivers/gpu/drm/i915/intel_hdcp.c
>> @@ -51,6 +51,10 @@ static int intel_hdcp_load_keys(struct drm_i915_private *dev_priv)
>>   	int ret;
>>   	u32 val;
>>   
>> +	val = I915_READ(HDCP_KEY_STATUS);
>> +	if ((val & HDCP_KEY_LOAD_DONE) && (val & HDCP_KEY_LOAD_STATUS))
>> +		return 0;
>> +
>>   	/*
>>   	 * On HSW and BDW HW loads the HDCP1.4 Key when Display comes
>>   	 * out of reset. So if Key is not already loaded, its an error state.
>> @@ -542,8 +546,6 @@ static int _intel_hdcp_disable(struct intel_connector *connector)
>>   		return -ETIMEDOUT;
>>   	}
>>   
>> -	intel_hdcp_clear_keys(dev_priv);
>> -
>>   	ret = connector->hdcp_shim->toggle_signalling(intel_dig_port, false);
>>   	if (ret) {
>>   		DRM_ERROR("Failed to disable HDCP signalling\n");
>> -- 
>> 2.7.4
>>

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