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

[Pali Rohár]

On Friday 01 July 2022 16:29:41 Pali Rohár wrote:
> 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.

Anything needed from me to improve this fix?

> > > Fixes: ec075262648f ("PCI: mvebu: Implement support for legacy INTx interrupts")
> > > Signed-off-by: Pali Rohár <pali@xxxxxxxxxx>
> > > ---
> > > Hello Bjorn! This is basically same issue as for pci-aardvark.c:
> > > https://lore.kernel.org/linux-pci/20220515125815.30157-1-pali@xxxxxxxxxx/#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
> > >