[Intel-gfx] [PATCH] drm/i915: Do not reset detect_done flag in intel_dp_detect

[Ville Syrjälä]

On Tue, Dec 06, 2016 at 04:43:51PM -0800, Manasi Navare wrote:
> The detect_done flag was introduced in the commit
> 7d23e3c37bb3fc6952dc84007ee60cb533fd2d5c in order to avoid
> multiple detects on hotplug where intel_dp_long_pulse()
> was called from HPD handler as well as in intel_dp_detect.
> So this detect_done flag was required to make sure intel_dp_detect()
> did not call long pulse handler again if it was already been called
> from HPD handler. However commit 1015811609c0328b5ed670d07748591b837e74eb
> differs the long hpd handling entirely until the hotplug work runs to
> avoid the double long hpd handling the "detect_done" flag is trying
> to prevent.

That sentence doesn't parse here. Anyways, the flag indeed is now a nop
and your patch is pretty much the same what I did here:
https://patchwork.freedesktop.org/patch/101476/

> 
> So now we do not need to reset the detect_done flag to false in
> intel_dp_detect. It will be reset in the intel_dp_hpd_pulse so
> that intel_dp_detect does a full detect. However if the .detect
> gets called during mode enumeration then we do not need to do a
> full detect. This patch avoids the WARNS_ONS during connected boot
> case when it calls intel_dp_check_link_status() due to multiple
> detects

How exactly does it do that? Also we shouldn't sweep that under the rug
anyway. Instead someone should actually fix the problem that causes the
WARN.

> and also avoids DP compliance failures. It avoids doing
> a full detect every single time on .detect().
> 
> Cc: Ville Syrjala <ville.syrjala at linux.intel.com>
> Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
> Cc: Jani Nikula <jani.nikula at linux.intel.com>
> Signed-off-by: Manasi Navare <manasi.d.navare at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c | 2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index db75bb9..9c9277e 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -4470,8 +4470,6 @@ static bool intel_digital_port_connected(struct drm_i915_private *dev_priv,
>  	if (!intel_dp->detect_done)
>  		status = intel_dp_long_pulse(intel_dp->attached_connector);
>  
> -	intel_dp->detect_done = false;
> -
>  	return status;
>  }
>  
> -- 
> 1.9.1

-- 
Ville Syrjälä
Intel OTC