linux-kernel - Re: [PATCH] drm: xlnx: zynqmp_dpsub: also call drm_helper_hpd_irq

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Message-ID: <e4626c1d3b28613d1d219c735bcd8525be0f0d9e.camel@dirkwinkel.cc>
Date: Wed, 25 Sep 2024 09:54:18 +0200
From: Steffen Dirkwinkel <lists@...ffen.cc>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: dri-devel@...ts.freedesktop.org, Maarten Lankhorst	
 <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
 Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>,
 Daniel Vetter <daniel@...ll.ch>, Michal Simek <michal.simek@....com>,
 linux-arm-kernel@...ts.infradead.org, 	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm: xlnx: zynqmp_dpsub: also call
 drm_helper_hpd_irq_event

Hi Laurent,

On Tue, 2024-09-24 at 21:43 +0300, Laurent Pinchart wrote:
> Hi Steffen,
> 
> Thank you for the patch.
> 
> On Mon, Sep 23, 2024 at 09:48:03AM +0200, lists@...ffen.cc wrote:
> > From: Steffen Dirkwinkel <s.dirkwinkel@...khoff.com>
> > 
> > With hpd going through the bridge as of commit eb2d64bfcc17
> > ("drm: xlnx: zynqmp_dpsub: Report HPD through the bridge")
> > we don't get hotplug events in userspace on zynqmp hardware.
> > Also sending hotplug events with drm_helper_hpd_irq_event works.
> 
> Why does the driver need to call both drm_helper_hpd_irq_event() and
> drm_bridge_hpd_notify() ? The latter should end up calling
> drm_kms_helper_connector_hotplug_event(), which is the same function
> that drm_helper_hpd_irq_event() calls.

I don't know why we need drm_helper_hpd_irq_event.
I'll try to trace what happens on hotplug.

> 
> > Fixes: eb2d64bfcc17 ("drm: xlnx: zynqmp_dpsub: Report HPD through
> > the bridge")
> > Signed-off-by: Steffen Dirkwinkel <s.dirkwinkel@...khoff.com>
> > ---
> >  drivers/gpu/drm/xlnx/zynqmp_dp.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c
> > b/drivers/gpu/drm/xlnx/zynqmp_dp.c
> > index 1846c4971fd8..cb823540a412 100644
> > --- a/drivers/gpu/drm/xlnx/zynqmp_dp.c
> > +++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c
> > @@ -17,6 +17,7 @@
> >  #include <drm/drm_fourcc.h>
> >  #include <drm/drm_modes.h>
> >  #include <drm/drm_of.h>
> > +#include <drm/drm_probe_helper.h>
> >  
> >  #include <linux/clk.h>
> >  #include <linux/delay.h>
> > @@ -1614,6 +1615,9 @@ static void zynqmp_dp_hpd_work_func(struct
> > work_struct *work)
> >  					    hpd_work.work);
> >  	enum drm_connector_status status;
> >  
> > +	if (dp->bridge.dev)
> > +		drm_helper_hpd_irq_event(dp->bridge.dev);
> > +
> >  	status = zynqmp_dp_bridge_detect(&dp->bridge);
> >  	drm_bridge_hpd_notify(&dp->bridge, status);
> >  }
>