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Date:   Thu, 17 Feb 2022 00:40:39 +0100
From:   Pali =?utf-8?B?Um9ow6Fy?= <pali@kernel.org>
To:     Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc:     robh+dt@kernel.org, Bjorn Helgaas <bhelgaas@google.com>,
        Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
        Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= <kw@linux.com>,
        Marek =?utf-8?B?QmVow7pu?= <kabel@kernel.org>,
        Russell King <rmk+kernel@armlinux.org.uk>,
        Marc Zyngier <maz@kernel.org>, linux-pci@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 10/11] PCI: mvebu: Implement support for legacy INTx
 interrupts
Message-ID: <20220216234039.stxv5ndd6ai23sbb@pali>
References: <20220105150239.9628-1-pali@kernel.org>
 <20220112151814.24361-1-pali@kernel.org>
 <20220112151814.24361-11-pali@kernel.org>
 <20220211171917.GA740@lpieralisi>
 <20220211175202.gku5pkwn5wmjo5al@pali>
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On Friday 11 February 2022 18:52:02 Pali Rohár wrote:
> On Friday 11 February 2022 17:19:17 Lorenzo Pieralisi wrote:
> > On Wed, Jan 12, 2022 at 04:18:13PM +0100, Pali Rohár wrote:
> > > This adds support for legacy INTx interrupts received from other PCIe
> > > devices and which are reported by a new INTx irq chip.
> > > 
> > > With this change, kernel can distinguish between INTA, INTB, INTC and INTD
> > > interrupts.
> > > 
> > > Note that for this support, device tree files has to be properly adjusted
> > > to provide "interrupts" or "interrupts-extended" property with intx
> > > interrupt source, "interrupt-names" property with "intx" string and also
> > > 'interrupt-controller' subnode must be defined.
> > > 
> > > If device tree files do not provide these nodes then driver would work as
> > > before.
> > 
> > Nit: this information is not useful. DT rules are written in DT
> > bindings, not in kernel commit logs. All I am saying is that firmware
> > developers should not have to read this log to write firmware.
> 
> It was not intended for firmware developers, but for reviewers of this
> patch to understand, what is happening in code and that with old DT
> files this patch does not change driver behavior (= work as before).
> 
> > > Signed-off-by: Pali Rohár <pali@kernel.org>
> > > ---
> > >  drivers/pci/controller/pci-mvebu.c | 185 +++++++++++++++++++++++++++--
> > >  1 file changed, 177 insertions(+), 8 deletions(-)
> > > 
> > > diff --git a/drivers/pci/controller/pci-mvebu.c b/drivers/pci/controller/pci-mvebu.c
> > > index 1e90ab888075..dbb6ecb4cb70 100644
> > > --- a/drivers/pci/controller/pci-mvebu.c
> > > +++ b/drivers/pci/controller/pci-mvebu.c
> > > @@ -54,9 +54,10 @@
> > >  	 PCIE_CONF_ADDR_EN)
> > >  #define PCIE_CONF_DATA_OFF	0x18fc
> > >  #define PCIE_INT_CAUSE_OFF	0x1900
> > > +#define PCIE_INT_UNMASK_OFF	0x1910
> > 
> > Nit: I understand it is tempting but here you are redefining or better
> > giving a proper label to a register. Separate patch please.
> 
> Ok!
> 
> > > +#define  PCIE_INT_INTX(i)		BIT(24+i)
> > >  #define  PCIE_INT_PM_PME		BIT(28)
> > > -#define PCIE_MASK_OFF		0x1910
> > 
> > See above.
> > 
> > > -#define  PCIE_MASK_ENABLE_INTS          0x0f000000
> > > +#define  PCIE_INT_ALL_MASK		GENMASK(31, 0)
> > >  #define PCIE_CTRL_OFF		0x1a00
> > >  #define  PCIE_CTRL_X1_MODE		0x0001
> > >  #define  PCIE_CTRL_RC_MODE		BIT(1)
> > > @@ -110,6 +111,9 @@ struct mvebu_pcie_port {
> > >  	struct mvebu_pcie_window iowin;
> > >  	u32 saved_pcie_stat;
> > >  	struct resource regs;
> > > +	struct irq_domain *intx_irq_domain;
> > > +	raw_spinlock_t irq_lock;
> > > +	int intx_irq;
> > >  };
> > >  
> > >  static inline void mvebu_writel(struct mvebu_pcie_port *port, u32 val, u32 reg)
> > > @@ -235,7 +239,7 @@ static void mvebu_pcie_setup_wins(struct mvebu_pcie_port *port)
> > >  
> > >  static void mvebu_pcie_setup_hw(struct mvebu_pcie_port *port)
> > >  {
> > > -	u32 ctrl, lnkcap, cmd, dev_rev, mask;
> > > +	u32 ctrl, lnkcap, cmd, dev_rev, unmask;
> > >  
> > >  	/* Setup PCIe controller to Root Complex mode. */
> > >  	ctrl = mvebu_readl(port, PCIE_CTRL_OFF);
> > > @@ -288,10 +292,30 @@ static void mvebu_pcie_setup_hw(struct mvebu_pcie_port *port)
> > >  	/* Point PCIe unit MBUS decode windows to DRAM space. */
> > >  	mvebu_pcie_setup_wins(port);
> > >  
> > > -	/* Enable interrupt lines A-D. */
> > > -	mask = mvebu_readl(port, PCIE_MASK_OFF);
> > > -	mask |= PCIE_MASK_ENABLE_INTS;
> > > -	mvebu_writel(port, mask, PCIE_MASK_OFF);
> > > +	/* Mask all interrupt sources. */
> > > +	mvebu_writel(port, ~PCIE_INT_ALL_MASK, PCIE_INT_UNMASK_OFF);
> > > +
> > > +	/* Clear all interrupt causes. */
> > > +	mvebu_writel(port, ~PCIE_INT_ALL_MASK, PCIE_INT_CAUSE_OFF);
> > > +
> > > +	if (port->intx_irq <= 0) {
> > > +		/*
> > > +		 * When neither "summary" interrupt, nor "intx" interrupt was
> > > +		 * specified in DT then unmask all legacy INTx interrupts as in
> > > +		 * this case driver does not provide a way for masking and
> > > +		 * unmasking of individual legacy INTx interrupts. In this case
> > > +		 * all interrupts, including legacy INTx are reported via one
> > > +		 * shared GIC source and therefore kernel cannot distinguish
> > > +		 * which individual legacy INTx was triggered. These interrupts
> > > +		 * are shared, so it should not cause any issue. Just
> > > +		 * performance penalty as every PCIe interrupt handler needs to
> > > +		 * be called when some interrupt is triggered.
> > > +		 */
> > 
> > This comment applies to current mainline right (ie it describes how
> > current mainline handles INTx) ? IMO you should split it out in a
> > separate patch.
> 
> This above comment describe what happens in if-branch when intx_irq is
> not set (as written in comment "when intx interrupt was not specified in
> DT"). You are right that this is also the behavior in the current
> mainline.
> 
> I'm not sure if this comment can be split out as support for "intx"
> interrupt is in this patch.
> 
> > I understand it is hard but a patch is a logical _change_, this
> > comment is a change per se, it is a clarification on current
> > behaviour.
> 
> Ok, I could try to split this comment into two patches, but part about
> if-branch comment needs to stay in "this" patch.

I have done it locally.

Let me know when I should resend this patch series and I will include
into it also these changes.

> > > +		unmask = mvebu_readl(port, PCIE_INT_UNMASK_OFF);
> > > +		unmask |= PCIE_INT_INTX(0) | PCIE_INT_INTX(1) |
> > > +			  PCIE_INT_INTX(2) | PCIE_INT_INTX(3);
> > > +		mvebu_writel(port, unmask, PCIE_INT_UNMASK_OFF);
> > > +	}
> > >  }
> > >  
> > >  static struct mvebu_pcie_port *mvebu_pcie_find_port(struct mvebu_pcie *pcie,
> > > @@ -924,6 +948,108 @@ static struct pci_ops mvebu_pcie_ops = {
> > >  	.write = mvebu_pcie_wr_conf,
> > >  };
> > >  
> > > +static void mvebu_pcie_intx_irq_mask(struct irq_data *d)
> > > +{
> > > +	struct mvebu_pcie_port *port = d->domain->host_data;
> > > +	irq_hw_number_t hwirq = irqd_to_hwirq(d);
> > > +	unsigned long flags;
> > > +	u32 unmask;
> > > +
> > > +	raw_spin_lock_irqsave(&port->irq_lock, flags);
> > > +	unmask = mvebu_readl(port, PCIE_INT_UNMASK_OFF);
> > > +	unmask &= ~PCIE_INT_INTX(hwirq);
> > > +	mvebu_writel(port, unmask, PCIE_INT_UNMASK_OFF);
> > > +	raw_spin_unlock_irqrestore(&port->irq_lock, flags);
> > > +}
> > > +
> > > +static void mvebu_pcie_intx_irq_unmask(struct irq_data *d)
> > > +{
> > > +	struct mvebu_pcie_port *port = d->domain->host_data;
> > > +	irq_hw_number_t hwirq = irqd_to_hwirq(d);
> > > +	unsigned long flags;
> > > +	u32 unmask;
> > > +
> > > +	raw_spin_lock_irqsave(&port->irq_lock, flags);
> > > +	unmask = mvebu_readl(port, PCIE_INT_UNMASK_OFF);
> > > +	unmask |= PCIE_INT_INTX(hwirq);
> > > +	mvebu_writel(port, unmask, PCIE_INT_UNMASK_OFF);
> > > +	raw_spin_unlock_irqrestore(&port->irq_lock, flags);
> > > +}
> > > +
> > > +static struct irq_chip intx_irq_chip = {
> > > +	.name = "mvebu-INTx",
> > > +	.irq_mask = mvebu_pcie_intx_irq_mask,
> > > +	.irq_unmask = mvebu_pcie_intx_irq_unmask,
> > > +};
> > > +
> > > +static int mvebu_pcie_intx_irq_map(struct irq_domain *h,
> > > +				   unsigned int virq, irq_hw_number_t hwirq)
> > > +{
> > > +	struct mvebu_pcie_port *port = h->host_data;
> > > +
> > > +	irq_set_status_flags(virq, IRQ_LEVEL);
> > > +	irq_set_chip_and_handler(virq, &intx_irq_chip, handle_level_irq);
> > > +	irq_set_chip_data(virq, port);
> > > +
> > > +	return 0;
> > > +}
> > > +
> > > +static const struct irq_domain_ops mvebu_pcie_intx_irq_domain_ops = {
> > > +	.map = mvebu_pcie_intx_irq_map,
> > > +	.xlate = irq_domain_xlate_onecell,
> > > +};
> > > +
> > > +static int mvebu_pcie_init_irq_domain(struct mvebu_pcie_port *port)
> > > +{
> > > +	struct device *dev = &port->pcie->pdev->dev;
> > > +	struct device_node *pcie_intc_node;
> > > +
> > > +	raw_spin_lock_init(&port->irq_lock);
> > > +
> > > +	pcie_intc_node = of_get_next_child(port->dn, NULL);
> > > +	if (!pcie_intc_node) {
> > > +		dev_err(dev, "No PCIe Intc node found for %s\n", port->name);
> > > +		return -ENODEV;
> > > +	}
> > > +
> > > +	port->intx_irq_domain = irq_domain_add_linear(pcie_intc_node, PCI_NUM_INTX,
> > > +						      &mvebu_pcie_intx_irq_domain_ops,
> > > +						      port);
> > > +	of_node_put(pcie_intc_node);
> > > +	if (!port->intx_irq_domain) {
> > > +		dev_err(dev, "Failed to get INTx IRQ domain for %s\n", port->name);
> > > +		return -ENOMEM;
> > > +	}
> > > +
> > > +	return 0;
> > > +}
> > > +
> > > +static void mvebu_pcie_irq_handler(struct irq_desc *desc)
> > > +{
> > > +	struct mvebu_pcie_port *port = irq_desc_get_handler_data(desc);
> > > +	struct irq_chip *chip = irq_desc_get_chip(desc);
> > > +	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;
> > > +
> > > +	/* Process legacy INTx interrupts */
> > > +	for (i = 0; i < PCI_NUM_INTX; i++) {
> > > +		if (!(status & PCIE_INT_INTX(i)))
> > > +			continue;
> > > +
> > > +		if (generic_handle_domain_irq(port->intx_irq_domain, i) == -EINVAL)
> > > +			dev_err_ratelimited(dev, "unexpected INT%c IRQ\n", (char)i+'A');
> > > +	}
> > > +
> > > +	chained_irq_exit(chip, desc);
> > > +}
> > > +
> > >  static int mvebu_pcie_map_irq(const struct pci_dev *dev, u8 slot, u8 pin)
> > >  {
> > >  	/* Interrupt support on mvebu emulated bridges is not implemented yet */
> > > @@ -1121,6 +1247,21 @@ static int mvebu_pcie_parse_port(struct mvebu_pcie *pcie,
> > >  		port->io_attr = -1;
> > >  	}
> > >  
> > > +	/*
> > > +	 * Old DT bindings do not contain "intx" interrupt
> > > +	 * so do not fail probing driver when interrupt does not exist.
> > > +	 */
> > > +	port->intx_irq = of_irq_get_byname(child, "intx");
> > > +	if (port->intx_irq == -EPROBE_DEFER) {
> > > +		ret = port->intx_irq;
> > > +		goto err;
> > > +	}
> > > +	if (port->intx_irq <= 0) {
> > > +		dev_warn(dev, "%s: legacy INTx interrupts cannot be masked individually, "
> > > +			      "%pOF does not contain intx interrupt\n",
> > > +			 port->name, child);
> > 
> > Here you end up with a new warning on existing firmware. Is it
> > legitimate ? I would remove the dev_warn().
> 
> I added this warning in v2 because Marc wanted it.
> 
> Should I (again) remove it in v3?
> 
> > Rob certainly has more insightful advice on this.
> > 
> > Thanks,
> > Lorenzo
> > 
> > > +	}
> > > +
> > >  	reset_gpio = of_get_named_gpio_flags(child, "reset-gpios", 0, &flags);
> > >  	if (reset_gpio == -EPROBE_DEFER) {
> > >  		ret = reset_gpio;
> > > @@ -1317,6 +1458,7 @@ static int mvebu_pcie_probe(struct platform_device *pdev)
> > >  
> > >  	for (i = 0; i < pcie->nports; i++) {
> > >  		struct mvebu_pcie_port *port = &pcie->ports[i];
> > > +		int irq = port->intx_irq;
> > >  
> > >  		child = port->dn;
> > >  		if (!child)
> > > @@ -1344,6 +1486,22 @@ static int mvebu_pcie_probe(struct platform_device *pdev)
> > >  			continue;
> > >  		}
> > >  
> > > +		if (irq > 0) {
> > > +			ret = mvebu_pcie_init_irq_domain(port);
> > > +			if (ret) {
> > > +				dev_err(dev, "%s: cannot init irq domain\n",
> > > +					port->name);
> > > +				pci_bridge_emul_cleanup(&port->bridge);
> > > +				devm_iounmap(dev, port->base);
> > > +				port->base = NULL;
> > > +				mvebu_pcie_powerdown(port);
> > > +				continue;
> > > +			}
> > > +			irq_set_chained_handler_and_data(irq,
> > > +							 mvebu_pcie_irq_handler,
> > > +							 port);
> > > +		}
> > > +
> > >  		/*
> > >  		 * PCIe topology exported by mvebu hw is quite complicated. In
> > >  		 * reality has something like N fully independent host bridges
> > > @@ -1448,6 +1606,7 @@ 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;
> > > @@ -1458,7 +1617,17 @@ static int mvebu_pcie_remove(struct platform_device *pdev)
> > >  		mvebu_writel(port, cmd, PCIE_CMD_OFF);
> > >  
> > >  		/* Mask all interrupt sources. */
> > > -		mvebu_writel(port, 0, PCIE_MASK_OFF);
> > > +		mvebu_writel(port, ~PCIE_INT_ALL_MASK, PCIE_INT_UNMASK_OFF);
> > > +
> > > +		/* 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);
> > >  
> > >  		/* Free config space for emulated root bridge. */
> > >  		pci_bridge_emul_cleanup(&port->bridge);
> > > -- 
> > > 2.20.1
> > >