[Intel-gfx] [PATCH] drm/i915: storm detection documentation update

[Sivakumar Thulasimani]

On 7/8/2015 8:50 PM, Daniel Vetter wrote:
> On Wed, Jul 08, 2015 at 06:54:06PM +0530, Sivakumar Thulasimani wrote:
>>
>> On 7/7/2015 5:01 PM, Daniel Vetter wrote:
>>> On Tue, Jul 07, 2015 at 04:10:49PM +0530, Sivakumar Thulasimani wrote:
>>>> From: "Thulasimani,Sivakumar" <sivakumar.thulasimani at intel.com>
>>>>
>>>> Update the hotplug documentation to explain that hotplug storm
>>>> is not expected for Display port panels and hence is not handled
>>>> in current code.
>>>>
>>>> Signed-off-by: Sivakumar Thulasimani <sivakumar.thulasimani at intel.com>
>>>> ---
>>>>   drivers/gpu/drm/i915/intel_hotplug.c |    4 ++++
>>>>   1 file changed, 4 insertions(+)
>>>>
>>>> diff --git a/drivers/gpu/drm/i915/intel_hotplug.c b/drivers/gpu/drm/i915/intel_hotplug.c
>>>> index bac91a1..7dc5e6a 100644
>>>> --- a/drivers/gpu/drm/i915/intel_hotplug.c
>>>> +++ b/drivers/gpu/drm/i915/intel_hotplug.c
>>>> @@ -66,6 +66,10 @@
>>>>    * while before being re-enabled. The intention is to mitigate issues raising
>>>>    * from broken hardware triggering massive amounts of interrupts and grinding
>>>>    * the system to a halt.
>>>> + *
>>>> + * Hotplug interrupt storm is not expected on Display port panel, hence the
>>>> + * current code only handles disabling and later enabling of HPD interrupts
>>>> + * for HDMI panels through the storm handling set of functions.
>>> This isn't accurate, we handle storms on everything _but_ DP (tv, vga,
>>> sdvo, ...). I'd go with
>>>
>>>   * Hotplug interrupt storm is not expected on Display port panel, hence the
>>>   * current code doesn't handle irq reenabling when a DP sink is connected
>>>   * and the hpd is handled by the DP callbacks. But on DP+ ports
>>>   * storms are still handled correctly in all other cases (e.g. due to HDMI
>>>   * sinks).
>>>
>>> Could still be improved I think.
>>>
>>> -Daniel
>>>
>> Sorry i don't get the "DP+" reference here. By DP+, do you mean dongles ?
>> passive dongles will report them selves as HDMI to respective detect
>> routines
>> active dongles will be still treated as DP hence not handling HPD will apply
>> to any
>> display connected through active dongle as well.
> DP+ is DP with support for HDMI with level shifter cables (i.e. all the
> ports on intel chips). I just wanted to make it clear that storm handling
> doesn't work if we have a confirmed DP sink on the port, but will work in
> any other cases (nothing or HDMI sink or DVI or whatever connected). Like
> I said some room for improvement ;-)
> -Daniel
how about the following ?

  * current implementation expects that hotplug interrupt storm will not be
  * seen when display port sink is connected, hence on platforms whose DP
  * callback is handled by i915_digport_work_func reenabling of hpd is not
  * performed ( it was never expected to be disabled in the first place ;) )
  * this is specific to DP sinks handled by this routine and any other display
  * such as HDMI or DVI enabled on the same port will have proper logic since
  * it will use i915_hotplug_work_func where this logic is handled.

please provide any corrections or new comment to be used, i'll upload a 
new patch with
the final approved text block.

-- 
regards,
Sivakumar