linux-kernel - Re: [PATCH V2 1/2] drm/bridge: adv7511: Allow IRQ to share GPIO pins

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Date: Tue, 5 Mar 2024 10:18:16 +0200
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: Adam Ford <aford173@...il.com>
Cc: dri-devel@...ts.freedesktop.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-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 1/2] drm/bridge: adv7511: Allow IRQ to share GPIO pins

Hello Adam,

Thank you for the patch.

On Mon, Mar 04, 2024 at 06:48:57PM -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 GPIO, it won't be registered and the
> hot-plug detect fails to function.
> 
> Currently, the handler reads two registers and blindly
> assumes one of them caused the interrupt and returns IRQ_HANDLED
> unless there is an error. In order to properly do this, the IRQ
> handler needs to check if it needs to handle the IRQ and return
> IRQ_NONE if there is nothing to handle.  With the check added
> and the return code properly indicating whether or not it there
> was an IRQ, the IRQF_SHARED can be set to share a GPIO IRQ.
> 
> Signed-off-by: Adam Ford <aford173@...il.com>

Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>

> ---
> V2:  Add check to see if there is IRQ data to handle
> 
> diff --git a/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c b/drivers/gpu/drm/bridge/adv7511/adv7511_drv.c
> index b5518ff97165..f3b4616a8fb6 100644
> --- 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 data */
> +	if (!(irq0 & (ADV7511_INT0_HPD | ADV7511_INT0_EDID_READY)) &&
> +	    !(irq1 & ADV7511_INT1_DDC_ERROR))
> +		return -ENODATA;
> +
>  	regmap_write(adv7511->regmap, ADV7511_REG_INT(0), irq0);
>  	regmap_write(adv7511->regmap, ADV7511_REG_INT(1), irq1);
>  
> @@ -1318,7 +1323,8 @@ 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),
>  						adv7511);
>  		if (ret)
>  			goto err_unregister_audio;

-- 
Regards,

Laurent Pinchart