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

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On Mon, Aug 20, 2012 at 5:19 AM, Jingoo Han <jg1.han@xxxxxxxxxxx> wrote:
> On Wednesday, August 08, 2012 12:54 PM Sean Paul wrote:
>>
>> 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.
>> 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?

>> 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

>>
>> Signed-off-by: Sean Paul <seanpaul@xxxxxxxxxxxx>
>> ---
>>  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
>
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