Re: [PATCH] drm/i915: Splitting intel_dp_check_link_status

[Daniel Vetter <daniel@ffwll.ch>]

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
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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