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Date:   Tue, 14 Jan 2020 15:37:34 +0000
From:   Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
To:     Srinath Mannam <srinath.mannam@broadcom.com>
Cc:     Bjorn Helgaas <bhelgaas@google.com>,
        Florian Fainelli <f.fainelli@gmail.com>,
        Ray Jui <rjui@broadcom.com>, Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Andy Shevchenko <andy.shevchenko@gmail.com>,
        Andrew Murray <andrew.murray@arm.com>,
        Arnd Bergmann <arnd@arndb.de>,
        bcm-kernel-feedback-list@broadcom.com, linux-pci@vger.kernel.org,
        devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, Ray Jui <ray.jui@broadcom.com>,
        maz@kernel.org
Subject: Re: [PATCH v4 2/6] PCI: iproc: Add INTx support with better modeling
Message-ID: <20200114153734.GA8268@e121166-lin.cambridge.arm.com>
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 <1576814058-30003-3-git-send-email-srinath.mannam@broadcom.com>
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[+Marc thanks to whom I can review this code with the required IRQ chip
knowledge]

On Fri, Dec 20, 2019 at 09:24:14AM +0530, Srinath Mannam wrote:
> From: Ray Jui <ray.jui@broadcom.com>
> 
> Add PCIe legacy interrupt INTx support to the iProc PCIe driver by
> modeling it with its own IRQ domain. All 4 interrupts INTA, INTB, INTC,
> INTD share the same interrupt line connected to the GIC in the system,
> while the status of each INTx can be obtained through the INTX CSR
> register
          ^
Missing a period.

> Signed-off-by: Ray Jui <ray.jui@broadcom.com>
> Signed-off-by: Srinath Mannam <srinath.mannam@broadcom.com>
> ---
>  drivers/pci/controller/pcie-iproc.c | 108 +++++++++++++++++++++++++++++++++++-
>  drivers/pci/controller/pcie-iproc.h |   6 ++
>  2 files changed, 112 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/controller/pcie-iproc.c b/drivers/pci/controller/pcie-iproc.c
> index 0a468c7..485967b 100644
> --- a/drivers/pci/controller/pcie-iproc.c
> +++ b/drivers/pci/controller/pcie-iproc.c
> @@ -14,6 +14,7 @@
>  #include <linux/delay.h>
>  #include <linux/interrupt.h>
>  #include <linux/irqchip/arm-gic-v3.h>
> +#include <linux/irqchip/chained_irq.h>
>  #include <linux/platform_device.h>
>  #include <linux/of_address.h>
>  #include <linux/of_pci.h>
> @@ -270,6 +271,7 @@ enum iproc_pcie_reg {
>  
>  	/* enable INTx */
>  	IPROC_PCIE_INTX_EN,
> +	IPROC_PCIE_INTX_CSR,
>  
>  	/* outbound address mapping */
>  	IPROC_PCIE_OARR0,
> @@ -314,6 +316,7 @@ static const u16 iproc_pcie_reg_paxb_bcma[] = {
>  	[IPROC_PCIE_CFG_ADDR]		= 0x1f8,
>  	[IPROC_PCIE_CFG_DATA]		= 0x1fc,
>  	[IPROC_PCIE_INTX_EN]		= 0x330,
> +	[IPROC_PCIE_INTX_CSR]		= 0x334,
>  	[IPROC_PCIE_LINK_STATUS]	= 0xf0c,
>  };
>  
> @@ -325,6 +328,7 @@ static const u16 iproc_pcie_reg_paxb[] = {
>  	[IPROC_PCIE_CFG_ADDR]		= 0x1f8,
>  	[IPROC_PCIE_CFG_DATA]		= 0x1fc,
>  	[IPROC_PCIE_INTX_EN]		= 0x330,
> +	[IPROC_PCIE_INTX_CSR]		= 0x334,
>  	[IPROC_PCIE_OARR0]		= 0xd20,
>  	[IPROC_PCIE_OMAP0]		= 0xd40,
>  	[IPROC_PCIE_OARR1]		= 0xd28,
> @@ -341,6 +345,7 @@ static const u16 iproc_pcie_reg_paxb_v2[] = {
>  	[IPROC_PCIE_CFG_ADDR]		= 0x1f8,
>  	[IPROC_PCIE_CFG_DATA]		= 0x1fc,
>  	[IPROC_PCIE_INTX_EN]		= 0x330,
> +	[IPROC_PCIE_INTX_CSR]		= 0x334,
>  	[IPROC_PCIE_OARR0]		= 0xd20,
>  	[IPROC_PCIE_OMAP0]		= 0xd40,
>  	[IPROC_PCIE_OARR1]		= 0xd28,
> @@ -846,9 +851,103 @@ static int iproc_pcie_check_link(struct iproc_pcie *pcie)
>  	return link_is_active ? 0 : -ENODEV;
>  }
>  
> -static void iproc_pcie_enable(struct iproc_pcie *pcie)
> +static int iproc_pcie_intx_map(struct irq_domain *domain, unsigned int irq,
> +			       irq_hw_number_t hwirq)
>  {
> +	irq_set_chip_and_handler(irq, &dummy_irq_chip, handle_simple_irq);

This looks wrong.

Don't tell me there are other PCI controllers drivers implementing this
code so you copied and pasted it; I know that and they are all wrong.

Legacy PCI IRQs are level IRQs so they must be masked/unmasked upon IRQ
entry/exit.

Therefore the IRQ chip representing your controller can't be a
dummy_irq_chip, that has no methods so no masking is implemented
through it and the flow handler must be handle_level_irq (which,
in turn takes care of masking the IRQ - handle_simple_irq does
not).

The IRQ chip in the PCI host bridge has to have a way to mask/unmask
specific IRQs, implement a proper IRQ chip for it please.

We are curious: Have you ever tested this change with a PCI driver
requesting a threaded IRQ ?

Thanks,
Lorenzo

> +	irq_set_chip_data(irq, domain->host_data);
> +
> +	return 0;
> +}
> +
> +static const struct irq_domain_ops intx_domain_ops = {
> +	.map = iproc_pcie_intx_map,
> +};
> +
> +static void iproc_pcie_isr(struct irq_desc *desc)
> +{
> +	struct irq_chip *chip = irq_desc_get_chip(desc);
> +	struct iproc_pcie *pcie;
> +	struct device *dev;
> +	unsigned long status;
> +	u32 bit, virq;
> +
> +	chained_irq_enter(chip, desc);
> +	pcie = irq_desc_get_handler_data(desc);
> +	dev = pcie->dev;
> +
> +	/* go through INTx A, B, C, D until all interrupts are handled */
> +	do {
> +		status = iproc_pcie_read_reg(pcie, IPROC_PCIE_INTX_CSR);
> +		for_each_set_bit(bit, &status, PCI_NUM_INTX) {
> +			virq = irq_find_mapping(pcie->irq_domain, bit);
> +			if (virq)
> +				generic_handle_irq(virq);
> +			else
> +				dev_err(dev, "unexpected INTx%u\n", bit);
> +		}
> +	} while ((status & SYS_RC_INTX_MASK) != 0);
> +
> +	chained_irq_exit(chip, desc);
> +}
> +
> +static int iproc_pcie_intx_enable(struct iproc_pcie *pcie)
> +{
> +	struct device *dev = pcie->dev;
> +	struct device_node *node;
> +	int ret;
> +
> +	/*
> +	 * BCMA devices do not map INTx the same way as platform devices. All
> +	 * BCMA needs below line to enable INTx
> +	 */
>  	iproc_pcie_write_reg(pcie, IPROC_PCIE_INTX_EN, SYS_RC_INTX_MASK);
> +
> +	node = of_get_compatible_child(dev->of_node, "brcm,iproc-intc");
> +	if (node)
> +		pcie->irq = of_irq_get(node, 0);
> +
> +	if (!node || pcie->irq <= 0)
> +		return 0;
> +
> +	/* set IRQ handler */
> +	irq_set_chained_handler_and_data(pcie->irq, iproc_pcie_isr, pcie);
> +
> +	/* add IRQ domain for INTx */
> +	pcie->irq_domain = irq_domain_add_linear(node, PCI_NUM_INTX,
> +						 &intx_domain_ops, pcie);
> +	if (!pcie->irq_domain) {
> +		dev_err(dev, "failed to add INTx IRQ domain\n");
> +		ret = -ENOMEM;
> +		goto err_rm_handler_data;
> +	}
> +
> +	return 0;
> +
> +err_rm_handler_data:
> +	of_node_put(node);
> +	irq_set_chained_handler_and_data(pcie->irq, NULL, NULL);
> +
> +	return ret;
> +}
> +
> +static void iproc_pcie_intx_disable(struct iproc_pcie *pcie)
> +{
> +	uint32_t offset, virq;
> +
> +	iproc_pcie_write_reg(pcie, IPROC_PCIE_INTX_EN, 0x0);
> +
> +	if (pcie->irq <= 0)
> +		return;
> +
> +	for (offset = 0; offset < PCI_NUM_INTX; offset++) {
> +		virq = irq_find_mapping(pcie->irq_domain, offset);
> +		if (virq)
> +			irq_dispose_mapping(virq);
> +	}
> +
> +	irq_domain_remove(pcie->irq_domain);
> +	irq_set_chained_handler_and_data(pcie->irq, NULL, NULL);
>  }
>  
>  static inline bool iproc_pcie_ob_is_valid(struct iproc_pcie *pcie,
> @@ -1518,7 +1617,11 @@ int iproc_pcie_setup(struct iproc_pcie *pcie, struct list_head *res)
>  		goto err_power_off_phy;
>  	}
>  
> -	iproc_pcie_enable(pcie);
> +	ret = iproc_pcie_intx_enable(pcie);
> +	if (ret) {
> +		dev_err(dev, "failed to enable INTx\n");
> +		goto err_power_off_phy;
> +	}
>  
>  	if (IS_ENABLED(CONFIG_PCI_MSI))
>  		if (iproc_pcie_msi_enable(pcie))
> @@ -1562,6 +1665,7 @@ int iproc_pcie_remove(struct iproc_pcie *pcie)
>  	pci_remove_root_bus(pcie->root_bus);
>  
>  	iproc_pcie_msi_disable(pcie);
> +	iproc_pcie_intx_disable(pcie);
>  
>  	phy_power_off(pcie->phy);
>  	phy_exit(pcie->phy);
> diff --git a/drivers/pci/controller/pcie-iproc.h b/drivers/pci/controller/pcie-iproc.h
> index 4f03ea5..103e568 100644
> --- a/drivers/pci/controller/pcie-iproc.h
> +++ b/drivers/pci/controller/pcie-iproc.h
> @@ -74,6 +74,9 @@ struct iproc_msi;
>   * @ib: inbound mapping related parameters
>   * @ib_map: outbound mapping region related parameters
>   *
> + * @irq: interrupt line wired to the generic GIC for INTx
> + * @irq_domain: IRQ domain for INTx
> + *
>   * @need_msi_steer: indicates additional configuration of the iProc PCIe
>   * controller is required to steer MSI writes to external interrupt controller
>   * @msi: MSI data
> @@ -102,6 +105,9 @@ struct iproc_pcie {
>  	struct iproc_pcie_ib ib;
>  	const struct iproc_pcie_ib_map *ib_map;
>  
> +	int irq;
> +	struct irq_domain *irq_domain;
> +
>  	bool need_msi_steer;
>  	struct iproc_msi *msi;
>  };
> -- 
> 2.7.4
>