linux-kernel - Re: [PATCH 1/2] drm/bridge: adv7511: Allow IRQ to share GPIO pins

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Message-ID: <20240228163153.GH9863@pendragon.ideasonboard.com>
Date: Wed, 28 Feb 2024 18:31:53 +0200
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Adam Ford <aford173@...il.com>
Cc: dri-devel@...ts.freedesktop.org, linux-arm-kernel@...ts.infradead.org,
	aford@...conembedded.com, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>, Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>,
	Andrzej Hajda <andrzej.hajda@...el.com>,
	Neil Armstrong <neil.armstrong@...aro.org>,
	Robert Foss <rfoss@...nel.org>, Jonas Karlman <jonas@...boo.se>,
	Jernej Skrabec <jernej.skrabec@...il.com>,
	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>,
	devicetree@...r.kernel.org, imx@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] drm/bridge: adv7511:  Allow IRQ to share GPIO pins

Hi Adam,

Thank you for the patch.

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@...il.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.

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;

	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