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Date: Sun, 3 Mar 2024 17:52:31 +0200
From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Adam Ford <aford173@gmail.com>
Cc: dri-devel@lists.freedesktop.org, linux-arm-kernel@lists.infradead.org,
	aford@beaconembedded.com, Rob Herring <robh@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Conor Dooley <conor+dt@kernel.org>, Shawn Guo <shawnguo@kernel.org>,
	Sascha Hauer <s.hauer@pengutronix.de>,
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	Fabio Estevam <festevam@gmail.com>,
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	Neil Armstrong <neil.armstrong@linaro.org>,
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	Jernej Skrabec <jernej.skrabec@gmail.com>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Maxime Ripard <mripard@kernel.org>,
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	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] drm/bridge: adv7511: Allow IRQ to share GPIO pins
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On Sun, Mar 03, 2024 at 09:44:03AM -0600, Adam Ford wrote:
> On Wed, Feb 28, 2024 at 10:31 AM Laurent Pinchart wrote:
> > On Wed, Feb 28, 2024 at 05:37:35AM -0600, Adam Ford wrote:
> > > The IRQ registration currently assumes that the GPIO is
> > > dedicated to it, but that may not necessarily be the case.
> > > If the board has another device sharing the IRQ, it won't be
> > > registered and the hot-plug detect fails.  This is easily
> > > fixed by add the IRQF_SHARED flag.
> > >
> > > Signed-off-by: Adam Ford <aford173@gmail.com>
> > >
> > > diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> > > index b5518ff97165..21f08b2ae265 100644
> > > --- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> > > +++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> > > @@ -1318,7 +1318,8 @@ static int adv7511_probe(struct i2c_client *i2c)
> > >
> > >               ret = devm_request_threaded_irq(dev, i2c->irq, NULL,
> > >                                               adv7511_irq_handler,
> > > -                                             IRQF_ONESHOT, dev_name(dev),
> > > +                                             IRQF_ONESHOT | IRQF_SHARED,
> > > +                                             dev_name(dev),
> >
> > This looks fine, but the IRQ handler doesn't.
> 
> Thanks for the review.
> 
> > static int adv7511_irq_process(struct adv7511 *adv7511, bool process_hpd)
> > {
> >         unsigned int irq0, irq1;
> >         int ret;
> >
> >         ret = regmap_read(adv7511->regmap, ADV7511_REG_INT(0), &irq0);
> >         if (ret < 0)
> >                 return ret;
> >
> >         ret = regmap_read(adv7511->regmap, ADV7511_REG_INT(1), &irq1);
> >         if (ret < 0)
> >                 return ret;
> 
> If I did a check here and returned if there was no IRQ to handle,
> would that be sufficient?
> 
> --- a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> +++ b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> @@ -477,6 +477,11 @@ static int adv7511_irq_process(struct adv7511
> *adv7511, bool process_hpd)
>         if (ret < 0)
>                 return ret;
> 
> +       /* If there is no IRQ to handle, exit indicating no IRQ handled */
> +       if (!(irq0 & (ADV7511_INT0_HPD | ADV7511_INT0_EDID_READY)) &&
> +          !(irq1 & ADV7511_INT1_DDC_ERROR))

If these are the only interrupt sources that the driver enables, this is
fine.

> +               return -1;

Maybe a defined error code instead ?

> +
>         regmap_write(adv7511->regmap, ADV7511_REG_INT(0), irq0);
>         regmap_write(adv7511->regmap, ADV7511_REG_INT(1), irq1);
> 
> With this, I would expect adv7511_irq_handler to return IRQ_NONE.  If
> you're OK with that approach, I can do that.  If you want me to merge
> adv7511_irq_handler, and adv7511_irq_process, I can do that too to
> make the return codes a little more intuitive.
> 
> >
> >         regmap_write(adv7511->regmap, ADV7511_REG_INT(0), irq0);
> >         regmap_write(adv7511->regmap, ADV7511_REG_INT(1), irq1);
> >
> >         if (process_hpd && irq0 & ADV7511_INT0_HPD && adv7511->bridge.encoder)
> >                 schedule_work(&adv7511->hpd_work);
> >
> >         if (irq0 & ADV7511_INT0_EDID_READY || irq1 & ADV7511_INT1_DDC_ERROR) {
> >                 adv7511->edid_read = true;
> >
> >                 if (adv7511->i2c_main->irq)
> >                         wake_up_all(&adv7511->wq);
> >         }
> >
> > #ifdef CONFIG_DRM_I2C_ADV7511_CEC
> >         adv7511_cec_irq_process(adv7511, irq1);
> > #endif
> >
> >         return 0;
> > }
> >
> > static irqreturn_t adv7511_irq_handler(int irq, void *devid)
> > {
> >         struct adv7511 *adv7511 = devid;
> >         int ret;
> >
> >         ret = adv7511_irq_process(adv7511, true);
> >         return ret < 0 ? IRQ_NONE : IRQ_HANDLED;
> > }
> >
> > The function will return IRQ_HANDLED as long as the registers can be
> > read, even if they don't report any interrupt.
> >
> > >                                               adv7511);
> > >               if (ret)
> > >                       goto err_unregister_audio;

-- 
Regards,

Laurent Pinchart