[Intel-gfx] [PATCH 5/6] drm/i915: read sink_count dpcd always

[Shubhangi Shrivastava]

On Monday 18 January 2016 06:14 PM, Shubhangi Shrivastava wrote:
>
>
> On Thursday 14 January 2016 06:34 PM, Ander Conselvan De Oliveira wrote:
>> On Tue, 2016-01-05 at 18:20 +0530, Shubhangi Shrivastava wrote:
>>> This patch reads sink_count dpcd always and removes its
>>> read operation based on values in downstream port dpcd.
>>>
>>> SINK_COUNT dpcd is not dependent on DOWNSTREAM_PORT_PRESENT dpcd.
>>> SINK_COUNT denotes if a display is attached, while
>>> DOWNSTREAM_PORT_PRESET indicates how many ports are available
>>> in the dongle where display can be attached. so it is possible
>>> for sink count to change irrespective of value in downstream
>>> port dpcd.
>>>
>>> Here is a table of possible values and scenarios
>>>
>>> sink_count      downstream_port
>>>                  present
>>> 0               0               no display is attached
>>> 0               1               dongle is connected without display
>>> 1               0               display connected directly
>>> 1               1               display connected through dongle
>>>
>>> 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 | 11 +++++++----
>>>   1 file changed, 7 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/intel_dp.c 
>>> b/drivers/gpu/drm/i915/intel_dp.c
>>> index c2e8516..0d58bfd 100644
>>> --- a/drivers/gpu/drm/i915/intel_dp.c
>>> +++ b/drivers/gpu/drm/i915/intel_dp.c
>>> @@ -3865,6 +3865,13 @@ intel_dp_get_dpcd(struct intel_dp *intel_dp)
>>>       if (intel_dp->dpcd[DP_DPCD_REV] == 0)
>>>           return false; /* DPCD not present */
>>>   +    if (intel_dp_dpcd_read_wake(&intel_dp->aux, DP_SINK_COUNT,
>>> +                    &intel_dp->sink_count, 1) < 0)
>>> +        return false;
>>> +
>>> +    if (!DP_GET_SINK_COUNT(intel_dp->sink_count))
>>> +        return false;
>>> +
>> My understanding is that this function should only read the DPCD data 
>> while
>> detection based on that data is done in intel_dp_detect_dpcd(). With 
>> the return
>> on sink_count == 0 here, we skip the end of the function, which 
>> updates the
>> cached downstream port information. Is there a reason why we need 
>> this early
>> return here?
>>
>> Also, I think this could be squashed with the previous patch.
>>
>> Ander
> As described in the commit message, if sink_count is 0, then there is 
> no display present. So, irrespective of value of downstream port, we 
> should terminate the function and thus, an early return is present here.
>
Squashing this patch with the previous one.
>>>       /* Check if the panel supports PSR */
>>>       memset(intel_dp->psr_dpcd, 0, sizeof(intel_dp->psr_dpcd));
>>>       if (is_edp(intel_dp)) {
>>> @@ -4386,10 +4393,6 @@ intel_dp_detect_dpcd(struct intel_dp *intel_dp)
>>>       if (intel_dp->dpcd[DP_DPCD_REV] >= 0x11 &&
>>>           intel_dp->downstream_ports[0] & DP_DS_PORT_HPD) {
>>>   -        if (intel_dp_dpcd_read_wake(&intel_dp->aux, DP_SINK_COUNT,
>>> -                        &intel_dp->sink_count, 1) < 0)
>>> -            return connector_status_unknown;
>>> -
>>>           return DP_GET_SINK_COUNT(intel_dp->sink_count) ?
>>>           connector_status_connected : connector_status_disconnected;
>>>       }
>