linux-kernel - Re: [PATCH 2/4] PCI: mvebu: Implement support for interrupts on emulated bridge

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Date:   Thu, 18 Aug 2022 21:51:21 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Pali Rohár <pali@...nel.org>
Cc:     Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Rob Herring <robh+dt@...nel.org>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        Gregory Clement <gregory.clement@...tlin.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        linux-pci@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/4] PCI: mvebu: Implement support for interrupts on
 emulated bridge

> -static irqreturn_t mvebu_pcie_irq_handler(int irq, void *arg)
> +static irqreturn_t mvebu_pcie_error_irq_handler(int irq, void *arg)
> +{
> +	struct mvebu_pcie_port *port = arg;
> +	struct device *dev = &port->pcie->pdev->dev;
> +	u32 cause, unmask, status;
> +
> +	cause = mvebu_readl(port, PCIE_INT_CAUSE_OFF);
> +	unmask = mvebu_readl(port, PCIE_INT_UNMASK_OFF);
> +	status = cause & unmask;
> +
> +	/* "error" interrupt handler does not process INTX interrupts */
> +	status &= ~(PCIE_INT_INTX(0) | PCIE_INT_INTX(1) |
> +		    PCIE_INT_INTX(2) | PCIE_INT_INTX(3));

Just for my understanding...

There are two interrupts, but the status information what those
interrupts actually mean are all packed into one register? I assume
reading the clause register does not clear set bits? Otherwise there
would be a race condition. Are these actually level interrupts, and in
order to clear them you need to poke some other register?

> +	/*
> +	 * Old DT bindings do not contain "error" interrupt
> +	 * so do not fail probing driver when interrupt does not exist.
> +	 */
> +	port->error_irq = of_irq_get_byname(child, "error");
> +	if (port->error_irq == -EPROBE_DEFER) {
> +		ret = port->error_irq;
> +		goto err;
> +	}
> +	if (port->error_irq <= 0) {
> +		dev_warn(dev, "%s: interrupts on Root Port are unsupported, "

Maybe that should be "Error interrupts on Root..." ?

      Andrew