Re: [PATCH v2 3/4] drm/i915: Check hdcp key loadability

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

On Monday 09 April 2018 01:58 PM, Daniel Vetter wrote:
> On Fri, Apr 06, 2018 at 07:02:02PM +0300, Ville Syrjälä wrote:
>> On Mon, Apr 02, 2018 at 02:35:42PM +0530, Ramalingam C wrote:
>>>
>>> On Thursday 29 March 2018 07:54 PM, Ville Syrjälä wrote:
>>>> On Thu, Mar 29, 2018 at 07:39:07PM +0530, Ramalingam C wrote:
>>>>> HDCP1.4 key can be loaded, only when Power well #1 is enabled and cdclk
>>>>> is enabled. Using the I915 power well infrastruture, above requirement
>>>>> is verified.
>>>>>
>>>>> This patch enables the hdcp initialization for HSW, BDW, and BXT.
>>>>>
>>>>> v2:
>>>>>     Choose the PW# based on the platform.
>>>>>
>>>>> Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
>>>>> Reviewed-by: Sean Paul <seanpaul@chromium.org>
>>>>> ---
>>>>>    drivers/gpu/drm/i915/intel_hdcp.c | 41 +++++++++++++++++++++++++++++++++++++--
>>>>>    1 file changed, 39 insertions(+), 2 deletions(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/i915/intel_hdcp.c b/drivers/gpu/drm/i915/intel_hdcp.c
>>>>> index f77d956b2b18..d8af09b46a44 100644
>>>>> --- a/drivers/gpu/drm/i915/intel_hdcp.c
>>>>> +++ b/drivers/gpu/drm/i915/intel_hdcp.c
>>>>> @@ -37,6 +37,43 @@ static int intel_hdcp_poll_ksv_fifo(struct intel_digital_port *intel_dig_port,
>>>>>    	return 0;
>>>>>    }
>>>>>    
>>>>> +static bool hdcp_key_loadable(struct drm_i915_private *dev_priv)
>>>>> +{
>>>>> +	struct i915_power_domains *power_domains = &dev_priv->power_domains;
>>>>> +	struct i915_power_well *power_well;
>>>>> +	enum i915_power_well_id id;
>>>>> +	bool enabled = false;
>>>>> +
>>>>> +	/*
>>>>> +	 * On HSW and BDW, Display HW loads the Key as soon as Display resumes.
>>>>> +	 * On all BXT+, SW can load the keys only when the PW#1 is turned on.
>>>>> +	 */
>>>>> +	if (IS_HASWELL(dev_priv) || IS_BROADWELL(dev_priv))
>>>>> +		id = HSW_DISP_PW_GLOBAL;
>>>>> +	else
>>>>> +		id = SKL_DISP_PW_1;
>>>>> +
>>>>> +	mutex_lock(&power_domains->lock);
>>>>> +
>>>>> +	/* PG1 (power well #1) needs to be enabled */
>>>>> +	for_each_power_well(dev_priv, power_well) {
>>>>> +		if (power_well->id == id) {
>>>>> +			enabled = power_well->ops->is_enabled(dev_priv,
>>>>> +							      power_well);
>>>>> +			break;
>>>>> +		}
>>>>> +	}
>>>>> +	mutex_unlock(&power_domains->lock);
>>>>> +
>>>>> +	/*
>>>>> +	 * Another req for hdcp key loadability is enabled state of pll for
>>>>> +	 * cdclk. Without active crtc we wont land here. So we are assuming that
>>>>> +	 * cdclk is already on.
>>>>> +	 */
>>>>> +
>>>>> +	return enabled;
>>>>> +}
>>>>> +
>>>>>    static void intel_hdcp_clear_keys(struct drm_i915_private *dev_priv)
>>>>>    {
>>>>>    	I915_WRITE(HDCP_KEY_CONF, HDCP_CLEAR_KEYS_TRIGGER);
>>>>> @@ -615,8 +652,8 @@ static int _intel_hdcp_enable(struct intel_connector *connector)
>>>>>    	DRM_DEBUG_KMS("[%s:%d] HDCP is being enabled...\n",
>>>>>    		      connector->base.name, connector->base.base.id);
>>>>>    
>>>>> -	if (!(I915_READ(SKL_FUSE_STATUS) & SKL_FUSE_PG_DIST_STATUS(1))) {
>>>>> -		DRM_ERROR("PG1 is disabled, cannot load keys\n");
>>>>> +	if (!hdcp_key_loadable(dev_priv)) {
>>>>> +		DRM_ERROR("HDCP key Load is not possible\n");
>>>>>    		return -ENXIO;
>>>>>    	}
>>>> If you need the power well then why aren't you grabbing the correct
>>>> power domain reference somewhere?
>>> Ville,
>>>
>>> As HDCP is supposed to be enabled after the basic display is up, power well #1 is supposed to be enabled.
>>> If not that is mostly an error w.r.t HDCP.
>>>
>>> So at this point we just want to verify whether required PW is up and HDCP key can be loaded from the HW. Else fail the HDCP request.
>> So this is in practice dead code to deal with a hypothetical bug
>> elsewhere in the driver?
> Yeah looks like it should be wrapped in a WARN_ON, or maybe outright
> thrown out. The unclaimed mmio debug stuff will catch when this happens
> (or well, should).
> -Daniel
Ok. Intention of this patch was generalizing the existing SKL specific 
PW check for all hdcp capable intel platforms.
Please suggest if this needs to be wrapped into WARN_ON or really want 
to discard it.

--Ram

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