RE: [PATCH 05/10] video: exynos_dp: Remove sink control to D0

On Thursday, November 01, 2012 2:05 AM Sean Paul wrote

On Mon, Aug 20, 2012 at 5:19 AM, Jingoo Han [off-list ref] wrote:

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On Wednesday, August 08, 2012 12:54 PM Sean Paul wrote:

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Don't reset the sink power to D0. Removing this for three reasons:

1) It's not required in the SW link training documentation

OK.

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2) The comment is incorrect, D0 is normal operation, not "power down"

OK. As you mentioned, D0 is not 'power down', 'normal operation'.
However, if comment is wrong, usually we fix comment, not remove it. :)

The datasheet doesn't mention this step at all. Furthermore, the
comment explains how it *should* work, so I think it's the code that
is in error. Do you know why this code is needed?

This is not requirement of the datasheet.
Also, D0 is not necessary for Link training.

Um, this is work-around for initial development.
Newly developed panel did not work, due to pane problem,
so this work-around was added.
However, the panel problem was fixed, so this code is
not necessary.

Please replace comment as below:

According to DP spec, it is not required in the Link Training procedure.


Best regards,
Jingoo Han

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3) It seems to change things in the link training that causes glitches

Um, it seems that this problem depends on LCD panel.
Other LCDs that I have tested do not have this kind of problem.
Please, modify this comment.

That was a red herring, it didn't cause the glitches, just made them
less obvious.

Sean

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Signed-off-by: Sean Paul <redacted>
---
 drivers/video/exynos/exynos_dp_core.c |    6 ------
 1 files changed, 0 insertions(+), 6 deletions(-)

diff --git a/drivers/video/exynos/exynos_dp_core.c b/drivers/video/exynos/exynos_dp_core.c
index 207bd7e..1c998d9 100644
--- a/drivers/video/exynos/exynos_dp_core.c
+++ b/drivers/video/exynos/exynos_dp_core.c

@@ -273,12 +273,6 @@ static int exynos_dp_link_start(struct exynos_dp_device *dp)
      for (lane = 0; lane < lane_count; lane++)
              dp->link_train.cr_loop[lane] = 0;

-     /* Set sink to D0 (Sink Not Ready) mode. */
-     ret = exynos_dp_write_byte_to_dpcd(dp, DPCD_ADDR_SINK_POWER_STATE,
-                             DPCD_SET_POWER_STATE_D0);
-     if (ret)
-             return ret;
-
      /* Set link rate and count as you want to establish*/
      exynos_dp_set_link_bandwidth(dp, dp->link_train.link_rate);
      exynos_dp_set_lane_count(dp, dp->link_train.lane_count);
--

1.7.7.3