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

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Date:   Mon, 31 Aug 2020 23:45:42 -0400
From:   Samuel Dionne-Riel <samuel@...nne-riel.com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     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 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.

> > 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)
 		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;
+
+	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!

-- 
Samuel Dionne-Riel