[RFC PATCH 1/4] drm/etnaviv: Prevent IRQ triggering at probe time on i.MX8MM

[Schrempf Frieder]

On 30.04.20 16:23, Daniel Baluta wrote:
> 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?

That's what I first thought, too. But then I found out, that merely 
enabling the clocks will clear the sparse interrupt and cause the 
handler not to be called during probe anymore.