Re: [PATCH v2 10/11] PCI: mvebu: Implement support for legacy INTx interrupts

[Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>]

On Tue, Feb 22, 2022 at 11:51:29AM +0100, Pali Rohár wrote:
> On Tuesday 22 February 2022 10:21:06 Lorenzo Pieralisi wrote:
> > On Thu, Feb 17, 2022 at 12:40:39AM +0100, Pali Rohár wrote:
> > > 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.
> > 
> > Hi,
> > 
> > yes please resend it and I will merge it.
> 
> Done!
> https://lore.kernel.org/linux-pci/20220222104625.28461-1-pali@kernel.org/T/#u

Can you rebase it please on top of my pci/mvebu branch ?

https://git.kernel.org/pub/scm/linux/kernel/git/lpieralisi/pci.git/

Forgive me, I forgot to mention that, thanks.

Lorenzo