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

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Date:   Mon, 7 Nov 2022 00:25:34 +0100
From:   Pali Rohár <pali@...nel.org>
To:     Bjorn Helgaas <bhelgaas@...gle.com>
Cc:     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 Tuesday 24 May 2022 14:28:17 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.
> 
> 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

Hello! Half year passed since introduced commit in Fixes line, issue is
still there and for pci-mvebu.c was not fixed yet. For pci-aardvark.c
was fixed.

I do not see any progress in alternative solution for this issue and
therefore this patch is still relevant.

Moreover requirement to use devm_request_irq() is needed also for other
pci-mvebu.c patches which are waiting on the list, due to nature of
shared interrupt line. For example:
https://lore.kernel.org/linux-pci/20220830123639.4zpvvvlrsaqs2rls@pali/

> 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
>