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Date:   Tue, 22 Feb 2022 10:21:06 +0000
From:   Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
To:     Pali =?iso-8859-1?Q?Roh=E1r?= <pali@kernel.org>
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 =?iso-8859-1?Q?Beh=FAn?= <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: <20220222102057.GA17238@lpieralisi>
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>
 <20220216234039.stxv5ndd6ai23sbb@pali>
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On Thu, Feb 17, 2022 at 12:40:39AM +0100, Pali Roh?r wrote:
> On Friday 11 February 2022 18:52:02 Pali Roh?r wrote:
> > On Friday 11 February 2022 17:19:17 Lorenzo Pieralisi wrote:
> > > On Wed, Jan 12, 2022 at 04:18:13PM +0100, Pali Roh?r 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 Roh?r <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.

Thanks,
Lorenzo