linux-kernel - Re: Boot failure on gru-scarlet-inx with 5.9-rc2

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Date:   Tue, 1 Sep 2020 17:42:49 +0100
From:   Lorenzo Pieralisi <lorenzo.pieralisi@....com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     Samuel Dionne-Riel <samuel@...nne-riel.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Rob Herring <robh@...nel.org>, devicetree@...r.kernel.org,
        Frank Rowand <frowand.list@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: Boot failure on gru-scarlet-inx with 5.9-rc2

On Tue, Sep 01, 2020 at 04:37:42PM +0100, Marc Zyngier wrote:
> On 2020-09-01 04:45, Samuel Dionne-Riel wrote:
> > On Mon, 31 Aug 2020 10:27:37 +0100
> > Marc Zyngier <maz@...nel.org> wrote:
> > > 
> > > Ah, so actually anything that *enables pcie* kills your system.
> > > Great investigative work!
> > > 
> > > >
> > > > And backed by a further bisection with this that points to
> > > > d84c572de1a360501d2e439ac632126f5facf59d being the actual change
> > > > that causes the tablet to fail to boot, as long as the pcie0 node is
> > > > identified as pci properly.
> > > >
> > > > I am unsure if I should add as a Cc everyone involved in that change
> > > > set, though the author (coincidentally) is already in the original
> > > > list of recipients.
> > > 
> > > I've deliberately moved Rob from Cc to To... ;-)
> > 
> > Thanks, I don't actually know who to write to exactly.
> 
> Given that this is a PCI regression, I guess the PCI maintainers
> are the likely victims. Adding Bjorn and Lorenzo to the list in
> addition to Rob.
> 
> You can find the relevant people by looking at the MAINTAINERS
> file.
> 
> > > > Any additional thoughts from this additional information?
> > > 
> > > What you could do is to start looking at which of the
> > > pci_is_root_bus() changes breaks PCIe on this system.  The fact that
> > > it breaks on your system and not on mine is a bit puzzling.
> > 
> > Let me show you, on top of v5.9-rc3 I can successfully boot using this
> > partial revert / adaptation of d84c572d. In addition, it also allows
> > the Wi-Fi to work again, compared to how it didn't in 5.9-rc1 or
> > 5.9-rc[23] with the dumb revert of your fix.
> > 
> > So, if we number each pci_is_root_bus by order appearance, it is only
> > the second use, in rockchip_pcie_valid_device, which seem to cause
> > scarlet not to boot.
> > 
> > The patch (not actually a patch submission) reverts only that instance
> > of pci_is_root_bus, while also doing some leg work to put back some
> > functionally equivalent code that was refactored away since.
> > 
> > If there's anything else you want me to try, don't hesitate.
> > 
> > ---
> >  drivers/pci/controller/pcie-rockchip-host.c | 8 +++++++-
> >  drivers/pci/controller/pcie-rockchip.h      | 1 +
> >  2 files changed, 8 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/pci/controller/pcie-rockchip-host.c
> > b/drivers/pci/controller/pcie-rockchip-host.c
> > index 0bb2fb3e8a0b..5a27fa833fbd 100644
> > --- a/drivers/pci/controller/pcie-rockchip-host.c
> > +++ b/drivers/pci/controller/pcie-rockchip-host.c
> > @@ -79,7 +79,7 @@ static int rockchip_pcie_valid_device(struct
> > rockchip_pcie *rockchip,
> >  	 * do not read more than one device on the bus directly attached
> >  	 * to RC's downstream side.
> >  	 */
> > -	if (pci_is_root_bus(bus->parent) && dev > 0)
> > +	if (bus->primary == rockchip->root_bus_nr && dev > 0)

Can you dump bus->primary when this condition is hit please ?

Also on a working system (ie prior to regression) please drop the output
of:

lspci -t

here.

> >  		return 0;
> > 
> >  	return 1;
> > @@ -944,6 +944,7 @@ static int rockchip_pcie_probe(struct
> > platform_device *pdev)
> >  	struct rockchip_pcie *rockchip;
> >  	struct device *dev = &pdev->dev;
> >  	struct pci_host_bridge *bridge;
> > +	struct resource *bus_res;
> >  	int err;
> > 
> >  	if (!dev->of_node)
> > @@ -983,6 +984,11 @@ static int rockchip_pcie_probe(struct
> > platform_device *pdev)
> >  	if (err < 0)
> >  		goto err_deinit_port;
> > 
> > +	/* HACK; ~equiv to last param of pci_parse_request_of_pci_ranges */
> > +	bus_res = (resource_list_first_type(&bridge->windows,
> > IORESOURCE_MEM))->res;

IORESOURCE_MEM ? I am a bit puzzled by this hack, what is it supposed
to do ?

> > +	rockchip->root_bus_nr = bus_res->start;
> > +
> >  	err = rockchip_pcie_cfg_atu(rockchip);
> >  	if (err)
> >  		goto err_remove_irq_domain;
> > diff --git a/drivers/pci/controller/pcie-rockchip.h
> > b/drivers/pci/controller/pcie-rockchip.h
> > index c7d0178fc8c2..0952fec7e34d 100644
> > --- a/drivers/pci/controller/pcie-rockchip.h
> > +++ b/drivers/pci/controller/pcie-rockchip.h
> > @@ -298,6 +298,7 @@ struct rockchip_pcie {
> >  	struct	gpio_desc *ep_gpio;
> >  	u32	lanes;
> >  	u8      lanes_map;
> > +	u8      root_bus_nr;
> >  	int	link_gen;
> >  	struct	device *dev;
> >  	struct	irq_domain *irq_domain;
> > --
> > 2.25.4
> > 
> > 
> > Thanks again!
> 
> Hmmm. It seems that the original commit (d84c572d) considered that
> root_bus_nr was always zero, while it may not have been.
> 
> Rob, Lorenzo: do you guys have any idea what is going on here?

That's a possibility - it would also be useful to have a look at
the DTS to check the bus-range property.

Thanks for reporting it,
Lorenzo