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Message-ID: <878rvsvoyo.wl-maz@kernel.org>
Date: Thu, 06 Jan 2022 15:55:11 +0000
From: Marc Zyngier <maz@...nel.org>
To: Pali Rohár <pali@...nel.org>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Rob Herring <robh+dt@...nel.org>,
Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
Krzysztof Wilczyński <kw@...ux.com>,
Marek Behún <kabel@...nel.org>,
Russell King <rmk+kernel@...linux.org.uk>,
linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 10/11] PCI: mvebu: Implement support for legacy INTx interrupts
On Thu, 06 Jan 2022 15:44:47 +0000,
Pali Rohár <pali@...nel.org> wrote:
>
> On Thursday 06 January 2022 15:28:20 Marc Zyngier wrote:
> > On Wed, 05 Jan 2022 15:02:38 +0000,
> > Pali Rohár <pali@...nel.org> 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.
> > >
> > > Signed-off-by: Pali Rohár <pali@...nel.org>
> > > ---
> > > drivers/pci/controller/pci-mvebu.c | 182 +++++++++++++++++++++++++++--
> > > 1 file changed, 174 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/drivers/pci/controller/pci-mvebu.c b/drivers/pci/controller/pci-mvebu.c
> > > index 1e90ab888075..04bcdd7b7a6d 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
> > > +#define PCIE_INT_INTX(i) BIT(24+i)
> > > #define PCIE_INT_PM_PME BIT(28)
> > > -#define PCIE_MASK_OFF 0x1910
> > > -#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 +111,10 @@ struct mvebu_pcie_port {
> > > struct mvebu_pcie_window iowin;
> > > u32 saved_pcie_stat;
> > > struct resource regs;
> > > + struct irq_domain *intx_irq_domain;
> > > + struct irq_chip intx_irq_chip;
> >
> > Why is this structure per port? It really should be global. Printing
> > the port number in the name isn't enough of a reason.
>
> Because each port has its own independent set of INTA-INTD
> interrupts.
That doesn't warrant a copy of an irq_chip structure that contains the
exact same callbacks, and only differs by *a string*. And the use of
this string is only to end-up in /proc/interrupts, which is totally
pointless.
>
> > > + raw_spinlock_t irq_lock;
> > > + int intx_irq;
> > > };
> > >
> > > static inline void mvebu_writel(struct mvebu_pcie_port *port, u32 val, u32 reg)
> > > @@ -235,7 +240,7 @@ 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 +293,30 @@ 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.
> > > + */
> > > + 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);
> >
> > Maybe worth printing a warning here, so that the user knows they are
> > on thin ice.
>
> Ok. I can add it here. Anyway, this is default current state without
> this patch.
>
> > > + }
> > > }
> > >
> > > static struct mvebu_pcie_port *mvebu_pcie_find_port(struct mvebu_pcie *pcie,
> > > @@ -924,6 +949,109 @@ 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 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, &port->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);
> > > +
> > > + port->intx_irq_chip.name = devm_kasprintf(dev, GFP_KERNEL,
> > > + "mvebu-%s-INTx",
> > > + port->name);
> >
> > That's exactly what I really don't want to see. It prevents sharing of
> > the irq_chip structure, and gets in the way of making it const in the
> > future. Yes, I know that some drivers do that. I can't fix those,
> > because /proc/interrupts is ABI. But I really don't want to see more
> > of these.
>
> Well, I do not understand why it should be shared and with who. HW has N
> independent IRQ chips for legacy interrupts. And each one will be
> specified in DT per HW layout / design.
If you have multiple ports, all the ports can share the irq_chip
structure. Actually scratch that. They *MUST* share the structure. The
only reason you're not sharing it is to be able to print this useless
string in /proc/interrupts.
M.
--
Without deviation from the norm, progress is not possible.
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