Re: [PATCH] drm: xlnx: zynqmp_dpsub: also call drm_helper_hpd_irq_event

[Steffen Dirkwinkel <lists@steffen.cc>]

On Sat, 2024-10-19 at 18:11 +0300, Dmitry Baryshkov wrote:
> On Wed, Oct 09, 2024 at 04:28:26PM +0200, Steffen Dirkwinkel wrote:
> > Hi Laurent,
> > 
> > 
> > On Wed, 2024-09-25 at 19:36 +0300, Laurent Pinchart wrote:
> > > Hi Steffen,
> > > 
> > > On Wed, Sep 25, 2024 at 09:54:18AM +0200, Steffen Dirkwinkel
> > > wrote:
> > > > On Tue, 2024-09-24 at 21:43 +0300, Laurent Pinchart wrote:
> > > > > On Mon, Sep 23, 2024 at 09:48:03AM +0200,
> > > > > lists@steffen.cc wrote:
> > > > > > From: Steffen Dirkwinkel <s.dirkwinkel@beckhoff.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.
> > > 
> > > Thank you. Let's try to find the best solution based on your
> > > findings.
> > 
> > There's just nothing registering for hpd with
> > "drm_bridge_connector_enable_hpd" or "drm_bridge_hpd_enable". I'm
> > not
> > sure what the correct way to implement this is. In
> > "drivers/gpu/drm/bridge/ti-tfp410.c" the driver registers for the
> > callback and calls "drm_helper_hpd_irq_event" in the callback. I
> > guess
> > we could also do that, but then we might as well call
> > drm_helper_hpd_irq_event directly? Some other drivers just call
> > both
> > like I did here. (drivers/gpu/drm/mediatek/mtk_hdmi.c for example)
> > For "drivers/gpu/drm/msm/hdmi/hdmi_bridge.c" I also can't find the
> > hpd
> > enable call and it just calls drm_bridge_hpd_notify.
> 
> The drm_bridge_connector handles enabling it for you when the driver
> calls drm_kms_helper_poll_init() / drm_kms_helper_poll_enable(). It
> seems zynqmp_kms calls drm_kms_helper_poll_init() too early, before
> creating DP chain, so the HPD doesn't get enabled.
Yes, that's it. Thank you

I'll send a patch for it.


> 
> > 
> > > 
> > > > > > Fixes: eb2d64bfcc17 ("drm: xlnx: zynqmp_dpsub: Report HPD
> > > > > > through
> > > > > > the bridge")
> > > > > > Signed-off-by: Steffen Dirkwinkel
> > > > > > <s.dirkwinkel@beckhoff.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);
> > > > > >  }
> > > 
> > 
>