linux-kernel - Re: [PATCH] PCI: Marvell: Update PCIe fixup

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Message-ID: <20211102094700.GA7376@alpha.franken.de>
Date:   Tue, 2 Nov 2021 10:47:00 +0100
From:   Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To:     Pali Rohár <pali@...nel.org>
Cc:     Russell King <linux@...linux.org.uk>, Andrew Lunn <andrew@...n.ch>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        Gregory Clement <gregory.clement@...tlin.com>,
        Jason Gunthorpe <jgg@...dia.com>,
        linux-arm-kernel@...ts.infradead.org, linux-mips@...r.kernel.org,
        linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: Marvell: Update PCIe fixup

On Tue, Nov 02, 2021 at 10:02:46AM +0100, Pali Rohár wrote:
> On Tuesday 02 November 2021 09:42:41 Thomas Bogendoerfer wrote:
> > On Mon, Nov 01, 2021 at 04:04:05PM +0100, Pali Rohár wrote:
> > > - The code relies on rc_pci_fixup being called, which only happens
> > >   when CONFIG_PCI_QUIRKS is enabled, so add that to Kconfig. Omitting
> > >   this causes a booting failure with a non-obvious cause.
> > > - Update rc_pci_fixup to set the class properly, copying the
> > >   more modern style from other places
> > > - Correct the rc_pci_fixup comment
> > > 
> > > This patch just re-applies commit 1dc831bf53fd ("ARM: Kirkwood: Update
> > > PCI-E fixup") for all other Marvell platforms which use same buggy PCIe
> > > controller.
> > > [..]
> > 
> > > diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
> > > index 771ca53af06d..c8d51bd20b84 100644
> > > --- a/arch/mips/Kconfig
> > > +++ b/arch/mips/Kconfig
> > > @@ -346,6 +346,7 @@ config MIPS_COBALT
> > >  	select CEVT_GT641XX
> > >  	select DMA_NONCOHERENT
> > >  	select FORCE_PCI
> > > +	select PCI_QUIRKS
> > >  	select I8253
> > >  	select I8259
> > >  	select IRQ_MIPS_CPU
> > 
> > this is enabled by default, via drivers/pci/Kconfig
> 
> IIRC 'default y' can be disabled but 'select' not.

overruled only if CONFIG_EXPERT is enabled, which IMHO sounds good enough.

> > config PCI_QUIRKS
> >         default y
> >         bool "Enable PCI quirk workarounds" if EXPERT
> >         help
> >           This enables workarounds for various PCI chipset bugs/quirks.
> >           Disable this only if your target machine is unaffected by PCI
> >           quirks.
> > 
> > > diff --git a/arch/mips/pci/fixup-cobalt.c b/arch/mips/pci/fixup-cobalt.c
> > > index 44be65c3e6bb..202f3a0bd97d 100644
> > > --- a/arch/mips/pci/fixup-cobalt.c
> > > +++ b/arch/mips/pci/fixup-cobalt.c
> > > @@ -36,6 +36,12 @@
> > >  #define VIA_COBALT_BRD_ID_REG  0x94
> > >  #define VIA_COBALT_BRD_REG_to_ID(reg)	((unsigned char)(reg) >> 4)
> > >  
> > > +/*
> > > + * The root complex has a hardwired class of PCI_CLASS_MEMORY_OTHER, when it
> > > + * is operating as a root complex this needs to be switched to
> > > + * PCI_CLASS_BRIDGE_HOST or Linux will errantly try to process the BAR's on
> > > + * the device. Decoding setup is handled by the orion code.
> > > + */
> > >  static void qube_raq_galileo_early_fixup(struct pci_dev *dev)
> > >  {
> > >  	if (dev->devfn == PCI_DEVFN(0, 0) &&
> > 
> > this is not a PCIe controller, so how is this patch related ?
> 
> I put that comment into all quirk code which is related to Marvell PCIe
> device XX:00.0 and changes PCI class type from PCI_CLASS_MEMORY_OTHER to
> PCI_CLASS_BRIDGE_HOST.
> 
> >From all what I saw, I'm sure that this device with this specific
> characteristics is really (non-compliant) Marvell PCIe controller.

just nitpicking, it's a Galileo PCI bridge and not PCIe.

> But I do not have this hardware to verify it.

I still have a few Cobalt systems here.

Thomas.

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