Re: [PATCH 17/19] PCI: rcar-gen2: Convert to use modern host bridge probe functions

Geert Uytterhoeven
2020-08-04T12:15:01Z

Hi Rob,

On Wed, Jul 22, 2020 at 4:26 AM Rob Herring <robh@kernel.org> wrote:
> The rcar-gen2 host driver still uses the old Arm PCI setup function
> pci_common_init_dev(). Let's update it to use the modern
> devm_pci_alloc_host_bridge(), pci_parse_request_of_pci_ranges() and
> pci_host_probe() functions.
>
> Cc: Marek Vasut <marek.vasut+renesas@gmail.com>
> Cc: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> Cc: Bjorn Helgaas <bhelgaas@google.com>
> Cc: linux-renesas-soc@vger.kernel.org
> Signed-off-by: Rob Herring <robh@kernel.org>

This is now commit 92d69cc6275845a7 ("PCI: rcar-gen2: Convert to use
modern host bridge probe functions"), and causes a crash on r8a7791/koelsch:

Unable to handle kernel NULL pointer dereference at virtual address 00000008
pgd = (ptrval)
[00000008] *pgd=00000000
Internal error: Oops: 5 [#1] SMP ARM
CPU: 0 PID: 1 Comm: swapper/0 Not tainted
5.8.0-rc1-shmobile-00035-g92d69cc6275845a7 #645
Hardware name: Generic R-Car Gen2 (Flattened Device Tree)
PC is at rcar_pci_probe+0x154/0x340
LR is at _raw_spin_unlock_irqrestore+0x18/0x20

> --- a/drivers/pci/controller/pci-rcar-gen2.c
> +++ b/drivers/pci/controller/pci-rcar-gen2.c
> @@ -189,19 +170,33 @@ static inline void rcar_pci_setup_errirq(struct rcar_pci_priv *priv) { }
> #endif
>
> /* PCI host controller setup */
> -static int rcar_pci_setup(int nr, struct pci_sys_data *sys)
> +static void rcar_pci_setup(struct rcar_pci_priv *priv)
> {
> - struct rcar_pci_priv *priv = sys->private_data;
> + struct pci_host_bridge *bridge = pci_host_bridge_from_priv(priv);
> struct device *dev = priv->dev;
> void __iomem *reg = priv->reg;
> + struct resource_entry *entry;
> + unsigned long window_size;
> + unsigned long window_addr;
> + unsigned long window_pci;
> u32 val;
> - int ret;
> +
> + entry = resource_list_first_type(&bridge->dma_ranges, IORESOURCE_MEM);

bridge->dma_ranges is not initialized => BOOM.

> static int rcar_pci_probe(struct platform_device *pdev)
> {
> struct device *dev = &pdev->dev;
> struct resource *cfg_res, *mem_res;
> struct rcar_pci_priv *priv;
> + struct pci_host_bridge *bridge;
> void __iomem *reg;
> - struct hw_pci hw;
> - void *hw_private[1];
> + int ret;
> +
> + bridge = devm_pci_alloc_host_bridge(dev, sizeof(*priv));
> + if (!bridge)
> + return -ENOMEM;
> +
> + priv = pci_host_bridge_priv(bridge);

This is the "new" priv instance.

> + bridge->sysdata = priv;
>
> cfg_res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> reg = devm_ioremap_resource(dev, cfg_res);

However, the "old" instance is still allocated below, and should be removed.

I've send a patch to fix that, which should appear soon at
https://lore.kernel.org/r/20200804120430.9253-1-geert+renesas@glider.be

BTW, the conversion has the following impact on r8a7791/koelsch:

-pci-rcar-gen2 ee090000.pci: PCI: bus0 revision 11
+pci-rcar-gen2 ee090000.pci: host bridge /soc/pci@ee090000 ranges:
+pci-rcar-gen2 ee090000.pci: MEM 0x00ee080000..0x00ee08ffff
-> 0x00ee080000
+pci-rcar-gen2 ee090000.pci: PCI: revision 11
pci-rcar-gen2 ee090000.pci: PCI host bridge to bus 0000:00
-pci_bus 0000:00: root bus resource [mem 0xee080000-0xee0810ff]
^^^^^^^^^^^^^^^^^^^^^
-pci_bus 0000:00: No busn resource found for root bus, will use [bus 00-ff]
+pci_bus 0000:00: root bus resource [bus 00]
+pci_bus 0000:00: root bus resource [mem 0xee080000-0xee08ffff]
^^^^^^^^^^^^^^^^^^^^^

pci0: pci@ee090000 {
...
reg = <0 0xee090000 0 0xc00>,
<0 0xee080000 0 0x1100>;
...
ranges = <0x02000000 0 0xee080000 0 0xee080000 0 0x00010000>;
...
usb@1,0 {
reg = <0x800 0 0 0 0>;
...
};

usb@2,0 {
reg = <0x1000 0 0 0 0>;
...
};

}

The old root bus resource size was based on the "reg" property.
The new root bus resource size is based on the "ranges" property.

Given the only children are hardcoded, I guess that is OK?

Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds