Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
From:   richard clark <richard.xnu.clark@gmail.com>
Date:   Wed, 25 May 2022 18:01:26 +0800
Message-ID: <CAJNi4rNwPQf747UM_hiYYwL=HDxg8QnPpfFPv1PfrtN9ZP1y1g@mail.gmail.com>
Subject: Question about SPIs' interrupt trigger type restrictions
To:     maz@kernel.org
Cc:     linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

Hi Marc,

For below code snippet about SPI interrupt trigger type:

static int gic_set_type(struct irq_data *d, unsigned int type)
{
        ...
        /* SPIs have restrictions on the supported types */
        if ((range == SPI_RANGE || range == ESPI_RANGE) &&
            type != IRQ_TYPE_LEVEL_HIGH && type != IRQ_TYPE_EDGE_RISING)
                return -EINVAL;
        ...
}

We have a device at hand whose interrupt type is SPI, Falling edge
will trigger the interrupt. But the request_irq(50, handler,
IRQ_TYPE_EDGE_FALLING, ...) will return -EINVAL.

The question is, why must the SPI interrupt use IRQ_TYPE_EDGE_RISING
instead of IRQ_TYPE_EDGE_FALLING?

Thanks,