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Subject: Re: [RFC PATCH 1/4] drm/etnaviv: Prevent IRQ triggering at probe time
 on i.MX8MM
To:     Schrempf Frieder <frieder.schrempf@kontron.de>,
        Adam Ford <aford173@gmail.com>,
        Anson Huang <Anson.Huang@nxp.com>,
        Christian Gmeiner <christian.gmeiner@gmail.com>,
        Fabio Estevam <festevam@gmail.com>,
        Leonard Crestez <leonard.crestez@nxp.com>,
        Li Jun <jun.li@nxp.com>, Lucas Stach <l.stach@pengutronix.de>,
        NXP Linux Team <linux-imx@nxp.com>,
        Peng Fan <peng.fan@nxp.com>,
        Pengutronix Kernel Team <kernel@pengutronix.de>,
        Russell King <linux+etnaviv@armlinux.org.uk>,
        Sascha Hauer <s.hauer@pengutronix.de>,
        Shawn Guo <shawnguo@kernel.org>,
        "S.j. Wang" <shengjiu.wang@nxp.com>
Cc:     "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
        "dri-devel@lists.freedesktop.org" <dri-devel@lists.freedesktop.org>,
        "etnaviv@lists.freedesktop.org" <etnaviv@lists.freedesktop.org>,
        "linux-arm-kernel@lists.infradead.org" 
        <linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
References: <20200430124602.14463-1-frieder.schrempf@kontron.de>
 <20200430124602.14463-2-frieder.schrempf@kontron.de>
From:   Daniel Baluta <daniel.baluta@nxp.com>
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Date:   Thu, 30 Apr 2020 17:23:46 +0300
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On 4/30/20 3:46 PM, Schrempf Frieder wrote:
>   
> +	/*
> +	 * On i.MX8MM there is an interrupt getting triggered immediately
> +	 * after requesting the IRQ, which leads to a stall as the handler
> +	 * accesses the GPU registers whithout the clock being enabled.
> +	 * Enabling the clocks briefly seems to clear the IRQ state, so we do
> +	 * this here before requesting the IRQ.
> +	 */
> +	err = etnaviv_gpu_clk_enable(gpu);
> +	if (err)
> +		return err;
> +
> +	err = etnaviv_gpu_clk_disable(gpu);
> +	if (err)
> +		return err;
> +
> +	err = devm_request_irq(&pdev->dev, gpu->irq, irq_handler, 0,
> +			       dev_name(gpu->dev), gpu);
> +	if (err) {
> +		dev_err(dev, "failed to request IRQ%u: %d\n", gpu->irq, err);
> +		return err;
> +	}

Shouldn't you disable the clk after devm_request_irq is called?