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Revert "drm/i915/dp: Use auxch precharge value of 5 everywhere"

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This reverts commit 092945e11c.

This commit prevents a DP screen from properly training the link.
Oddly enough it works, once the machine has been warm-booted with an
older kernel.

According to DP docs this _should_ have been the right precharge time.
Also, the commit that originally introduces this was just general snb
DP enabling and didn't mention any specific reason for this special
value. Whatever, trust the reporter that this makes things worse and
let's just revert it.

v2: Less spelling fail.

Cc: Adam Jackson <ajax@redhat.com>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Reported-by: "Wouter M. Koolen" <W.M.Koolen-Wijkstra@cwi.nl>
Buglink: https://lkml.org/lkml/2012/6/14/301
Cc: stable@vger.kernel.org (only for 3.4)
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
This commit is contained in:
Daniel Vetter 2012-06-14 22:15:00 +02:00
parent 351cfc34db
commit 6b4e0a93ff
1 changed files with 6 additions and 1 deletions
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7
drivers/gpu/drm/i915/intel_dp.c
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@ -371,7 +371,7 @@ intel_dp_aux_ch(struct intel_dp *intel_dp,
int recv_bytes;
uint32_t status;
uint32_t aux_clock_divider;
int try, precharge = 5;
int try, precharge;
intel_dp_check_edp(intel_dp);
/* The clock divider is based off the hrawclk,
@ -391,6 +391,11 @@ intel_dp_aux_ch(struct intel_dp *intel_dp,
else
aux_clock_divider = intel_hrawclk(dev) / 2;
if (IS_GEN6(dev))
precharge = 3;
else
precharge = 5;
/* Try to wait for any previous AUX channel activity */
for (try = 0; try < 3; try++) {
status = I915_READ(ch_ctl);