linux-kernel - Re: [PATCH] drm/komeda: Enable/Disable vblank interrupts

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Message-ID: <20190613142740.GA32394@arm.com>
Date:   Thu, 13 Jun 2019 14:27:41 +0000
From:   Ayan Halder <Ayan.Halder@....com>
To:     "james qian wang (Arm Technology China)" <james.qian.wang@....com>,
        Liviu Dudau <Liviu.Dudau@....com>,
        Brian Starkey <Brian.Starkey@....com>,
        "airlied@...ux.ie" <airlied@...ux.ie>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        nd <nd@....com>
Subject: Re: [PATCH] drm/komeda: Enable/Disable vblank interrupts

On Fri, Jun 07, 2019 at 08:18:56PM +0200, Daniel Vetter wrote:

Hi Daniel,

> On Fri, Jun 07, 2019 at 03:03:39PM +0000, Ayan Halder wrote:
> > One needs to set "(struct drm_device *)->irq_enabled = true" to signal drm core
> > to enable vblank interrupts after the hardware has been initialized.
> > Correspondingly, one needs to disable vblank interrupts by setting
> > "(struct drm_device *)->irq_enabled = false" at the beginning of the
> > de-initializing routine.
>
> Only if you don't use the drm_irq_install helper. Quoting the kerneldoc in
> full:
>
> /**
>  * @irq_enabled:
>  *
>  * Indicates that interrupt handling is enabled, specifically vblank
>  * handling. Drivers which don't use drm_irq_install() need to set this
>  * to true manually.
>  */
> bool irq_enabled;
>
> Not entirely sure where you've found your quote, but it's not complete.
>
> Cheers, Daniel

Thanks for your review.

That was my quote which reflects my half-baked understanding of the
issue :(. I had missed reading the header files.

That said, I will squash my previous patch "drm/komeda: Avoid using
DRIVER_IRQ_SHARED" into this one as the current patch is a consequence
of the changes made in the previous patch.

Regards,
Ayan Kumar Halder
>
> >
> > Signed-off-by: Ayan Kumar halder <ayan.halder@....com>
> > ---
> >  drivers/gpu/drm/arm/display/komeda/komeda_kms.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/arm/display/komeda/komeda_kms.c b/drivers/gpu/drm/arm/display/komeda/komeda_kms.c
> > index 7b5cde14e3ba..b4fd8ee0d05f 100644
> > --- a/drivers/gpu/drm/arm/display/komeda/komeda_kms.c
> > +++ b/drivers/gpu/drm/arm/display/komeda/komeda_kms.c
> > @@ -204,6 +204,8 @@ struct komeda_kms_dev *komeda_kms_attach(struct komeda_dev *mdev)
> >  if (err)
> >  goto uninstall_irq;
> >
> > +drm->irq_enabled = true;
> > +
> >  err = drm_dev_register(drm, 0);
> >  if (err)
> >  goto uninstall_irq;
> > @@ -211,6 +213,7 @@ struct komeda_kms_dev *komeda_kms_attach(struct komeda_dev *mdev)
> >  return kms;
> >
> >  uninstall_irq:
> > +drm->irq_enabled = false;
> >  drm_irq_uninstall(drm);
> >  cleanup_mode_config:
> >  drm_mode_config_cleanup(drm);
> > @@ -225,6 +228,7 @@ void komeda_kms_detach(struct komeda_kms_dev *kms)
> >  struct drm_device *drm = &kms->base;
> >  struct komeda_dev *mdev = drm->dev_private;
> >
> > +drm->irq_enabled = false;
> >  mdev->funcs->disable_irq(mdev);
> >  drm_dev_unregister(drm);
> >  drm_irq_uninstall(drm);
> > --
> > 2.21.0
> >
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch
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