linux-kernel - Re: [PATCH] PCI: mvebu: Use devm_request_irq() for registering interrupt handler

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Date:   Fri, 1 Jul 2022 16:29:41 +0200
From:   Pali Rohár <pali@...nel.org>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: mvebu: Use devm_request_irq() for registering
 interrupt handler

On Thursday 23 June 2022 11:27:47 Bjorn Helgaas wrote:
> On Tue, May 24, 2022 at 02:28:17PM +0200, Pali Rohár wrote:
> > Same as in commit a3b69dd0ad62 ("Revert "PCI: aardvark: Rewrite IRQ code to
> > chained IRQ handler"") for pci-aardvark driver, use devm_request_irq()
> > instead of chained IRQ handler in pci-mvebu.c driver.
> >
> > This change fixes affinity support and allows to pin interrupts from
> > different PCIe controllers to different CPU cores.
> 
> Several other drivers use irq_set_chained_handler_and_data().  Do any
> of them need similar changes?  The commit log suggests that using
> chained IRQ handlers breaks affinity support.  But perhaps that's not
> the case and the real culprit is some other difference between mvebu
> and the other drivers.

And there is another reason to not use irq_set_chained_handler_and_data
and instead use devm_request_irq(). Armada XP has some interrupts
shared and it looks like that irq_set_chained_handler_and_data() API
does not handle shared interrupt sources too.

I can update commit message to mention also this fact.

> > Fixes: ec075262648f ("PCI: mvebu: Implement support for legacy INTx interrupts")
> > Signed-off-by: Pali Rohár <pali@...nel.org>
> > ---
> > Hello Bjorn! This is basically same issue as for pci-aardvark.c:
> > https://lore.kernel.org/linux-pci/20220515125815.30157-1-pali@kernel.org/#t
> > 
> > I tested this patch with pci=nomsi in cmdline (to force kernel to use
> > legacy intx instead of MSI) on A385 and checked that I can set affinity
> > via /proc/irq/XX/smp_affinity file for every mvebu pcie controller to
> > different CPU and legacy interrupts from different cards/controllers
> > were handled by different CPUs.
> > 
> > I think that this is important on Armada XP platforms which have many
> > independent PCIe controllers (IIRC up to 10) and many cores (up to 4).
> > ---
> >  drivers/pci/controller/pci-mvebu.c | 30 +++++++++++++++++-------------
> >  1 file changed, 17 insertions(+), 13 deletions(-)
> > 
> > diff --git a/drivers/pci/controller/pci-mvebu.c b/drivers/pci/controller/pci-mvebu.c
> > index 8f76d4bda356..de67ea39fea5 100644
> > --- a/drivers/pci/controller/pci-mvebu.c
> > +++ b/drivers/pci/controller/pci-mvebu.c
> > @@ -1017,16 +1017,13 @@ static int mvebu_pcie_init_irq_domain(struct mvebu_pcie_port *port)
> >  	return 0;
> >  }
> >  
> > -static void mvebu_pcie_irq_handler(struct irq_desc *desc)
> > +static irqreturn_t mvebu_pcie_irq_handler(int irq, void *arg)
> >  {
> > -	struct mvebu_pcie_port *port = irq_desc_get_handler_data(desc);
> > -	struct irq_chip *chip = irq_desc_get_chip(desc);
> > +	struct mvebu_pcie_port *port = arg;
> >  	struct device *dev = &port->pcie->pdev->dev;
> >  	u32 cause, unmask, status;
> >  	int i;
> >  
> > -	chained_irq_enter(chip, desc);
> > -
> >  	cause = mvebu_readl(port, PCIE_INT_CAUSE_OFF);
> >  	unmask = mvebu_readl(port, PCIE_INT_UNMASK_OFF);
> >  	status = cause & unmask;
> > @@ -1040,7 +1037,7 @@ static void mvebu_pcie_irq_handler(struct irq_desc *desc)
> >  			dev_err_ratelimited(dev, "unexpected INT%c IRQ\n", (char)i+'A');
> >  	}
> >  
> > -	chained_irq_exit(chip, desc);
> > +	return status ? IRQ_HANDLED : IRQ_NONE;
> >  }
> >  
> >  static int mvebu_pcie_map_irq(const struct pci_dev *dev, u8 slot, u8 pin)
> > @@ -1490,9 +1487,20 @@ static int mvebu_pcie_probe(struct platform_device *pdev)
> >  				mvebu_pcie_powerdown(port);
> >  				continue;
> >  			}
> > -			irq_set_chained_handler_and_data(irq,
> > -							 mvebu_pcie_irq_handler,
> > -							 port);
> > +
> > +			ret = devm_request_irq(dev, irq, mvebu_pcie_irq_handler,
> > +					       IRQF_SHARED | IRQF_NO_THREAD,
> > +					       port->name, port);
> > +			if (ret) {
> > +				dev_err(dev, "%s: cannot register interrupt handler: %d\n",
> > +					port->name, ret);
> > +				irq_domain_remove(port->intx_irq_domain);
> > +				pci_bridge_emul_cleanup(&port->bridge);
> > +				devm_iounmap(dev, port->base);
> > +				port->base = NULL;
> > +				mvebu_pcie_powerdown(port);
> > +				continue;
> > +			}
> >  		}
> >  
> >  		/*
> > @@ -1599,7 +1607,6 @@ static int mvebu_pcie_remove(struct platform_device *pdev)
> >  
> >  	for (i = 0; i < pcie->nports; i++) {
> >  		struct mvebu_pcie_port *port = &pcie->ports[i];
> > -		int irq = port->intx_irq;
> >  
> >  		if (!port->base)
> >  			continue;
> > @@ -1615,9 +1622,6 @@ static int mvebu_pcie_remove(struct platform_device *pdev)
> >  		/* Clear all interrupt causes. */
> >  		mvebu_writel(port, ~PCIE_INT_ALL_MASK, PCIE_INT_CAUSE_OFF);
> >  
> > -		if (irq > 0)
> > -			irq_set_chained_handler_and_data(irq, NULL, NULL);
> > -
> >  		/* Remove IRQ domains. */
> >  		if (port->intx_irq_domain)
> >  			irq_domain_remove(port->intx_irq_domain);
> > -- 
> > 2.20.1
> >