Re: [PATCH] drm/i915: Splitting intel_dp_check_link_status

["Thulasimani, Sivakumar" <sivakumar.thulasimani@intel.com>]

On 1/19/2016 2:14 PM, Daniel Vetter wrote:
> On Tue, Jan 19, 2016 at 10:14:30AM +0530, Thulasimani, Sivakumar wrote:
>>
>> On 1/19/2016 2:35 AM, Lukas Wunner wrote:
>>> Hi,
>>>
>>> On Mon, Jan 18, 2016 at 04:22:19PM +0530, Shubhangi Shrivastava wrote:
>>>> When created originally intel_dp_check_link_status()
>>>> was supposed to handle only link training for short
>>>> pulse but has grown into handler for short pulse itself.
>>>> This patch cleans up this function by splitting it into
>>>> two halves. First intel_dp_short_pulse() is called,
>>>> which will be entry point and handle all logic for
>>>> short pulse handling while intel_dp_check_link_status()
>>>> will retain its original purpose of only doing link
>>>> status related work.
>>>> The link retraining part when EQ is not correct is
>>>> retained to intel_dp_check_link_status whereas other
>>>> operations are handled as part of intel_dp_short_pulse.
>>>> This change is required to avoid performing all DPCD
>>>> related operations on performing link retraining.
>>>>
>>>> v2: Added WARN_ON to intel_dp_check_link_status()
>>>>      Removed a call to intel_dp_get_link_status() (Ander)
>>>>
>>>> Tested-by: Nathan D Ciobanu <nathan.d.ciobanu@intel.com>
>>>> Signed-off-by: Sivakumar Thulasimani <sivakumar.thulasimani@intel.com>
>>>> Signed-off-by: Shubhangi Shrivastava <shubhangi.shrivastava@intel.com>
>>>> ---
>>>>   drivers/gpu/drm/i915/intel_dp.c | 65 +++++++++++++++++++++++------------------
>>>>   1 file changed, 36 insertions(+), 29 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
>>>> index 82ee18d..f8d9611 100644
>>>> --- a/drivers/gpu/drm/i915/intel_dp.c
>>>> +++ b/drivers/gpu/drm/i915/intel_dp.c
>>>> @@ -4279,6 +4279,36 @@ go_again:
>>>>   	return -EINVAL;
>>>>   }
>>>> +static void
>>>> +intel_dp_check_link_status(struct intel_dp *intel_dp)
>>>> +{
>>>> +	struct intel_encoder *intel_encoder = &dp_to_dig_port(intel_dp)->base;
>>>> +	struct drm_device *dev = intel_dp_to_dev(intel_dp);
>>>> +	u8 link_status[DP_LINK_STATUS_SIZE];
>>>> +
>>>> +	WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
>>>> +
>>>> +	if (!intel_dp_get_link_status(intel_dp, link_status)) {
>>>> +		DRM_ERROR("Failed to get link status\n");
>>>> +		return;
>>>> +	}
>>>> +
>>>> +	if (!intel_encoder->base.crtc)
>>>> +		return;
>>>> +
>>>> +	if (!to_intel_crtc(intel_encoder->base.crtc)->active)
>>>> +		return;
>>> Why do you change the order of the three if-clauses above?
>>> The original order seems to make more sense. (Checking for
>>> ->base.crtc and ->active is cheap, whereas accessing AUX to
>>> get the link status is time consuming. You don't want to
>>> spend that time only to bail out, should one of the other two
>>> if-clauses fail.)
>>>
>>> Best regards,
>>>
>>> Lukas
>> Actually it is expected to read link status whenever we receive short pulse
>> interrupt
>> irrespective of the panel being enabled or not. So this change is with
>> respect to
>> that rather than any performance based.
> As a general rule please don't make functional changes like these in a
> patch that just splits stuff up. Your patch summary sounds like simple
> refactoring, which this doesn't seem to be.
> -Daniel
Understood, will make the appropriate changes and move that to separate 
patch.

regards,
Sivakumar
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