[Intel-gfx] [PATCH] drm/i915: Splitting intel_dp_check_link_status

[Daniel Vetter]

On Tue, Jan 19, 2016 at 02:29:22PM +0530, Thulasimani, Sivakumar wrote:
> 
> 
> 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 at intel.com>
> >>>>Signed-off-by: Sivakumar Thulasimani <sivakumar.thulasimani at intel.com>
> >>>>Signed-off-by: Shubhangi Shrivastava <shubhangi.shrivastava at 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.

btw you don't have to split it since really this is a small change.
Changing the subject to something that makes is clearer that it's not just
refactoring is also ok, e.g. "reorganize intel_dp_detect"

Then explain in the commit message why and what changes, like you do
already.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch