[PATCH 2/3] staging: mt7621-pci: use generic kernel pci subsystem read and write

[NeilBrown]

On Tue, Jul 10 2018, Sergio Paracuellos wrote:

> map_bus callback is called before every .read/.write operation.
> Implement it and change custom read write operations for the
> pci subsystem generics. Make the probe function to assign data
> for controller data and get pci register base from device tree.
>
> Signed-off-by: Sergio Paracuellos <sergio.paracuellos at gmail.com>
> ---
>  drivers/staging/mt7621-pci/pci-mt7621.c | 76 +++++++++++++++++++++++++++++++--
>  1 file changed, 72 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/staging/mt7621-pci/pci-mt7621.c b/drivers/staging/mt7621-pci/pci-mt7621.c
> index 58c77bd..7bd06a0 100644
> --- a/drivers/staging/mt7621-pci/pci-mt7621.c
> +++ b/drivers/staging/mt7621-pci/pci-mt7621.c
> @@ -52,6 +52,9 @@
>  #include <linux/delay.h>
>  #include <linux/of.h>
>  #include <linux/of_pci.h>
> +#include <linux/of_platform.h>
> +#include <linux/of_address.h>
> +#include <linux/of_irq.h>
>  #include <linux/platform_device.h>
>  
>  #include <ralink_regs.h>
> @@ -306,15 +309,31 @@ pci_config_write(struct pci_bus *bus, unsigned int devfn, int where, int size, u
>  	}
>  }
>  
> +static void __iomem *mt7621_pcie_map_bus(struct pci_bus *bus,
> +					 unsigned int devfn, int where)
> +{
> +	struct mt7621_pcie_port *port = bus->sysdata;
> +	u32 address = mt7621_pci_get_cfgaddr(bus->number, PCI_SLOT(devfn),
> +					     PCI_FUNC(devfn), where);
> +	u32 address_reg, data_reg;
> +
> +	address_reg = RALINK_PCI_CONFIG_ADDR;
> +	data_reg = RALINK_PCI_CONFIG_DATA_VIRTUAL_REG;
> +
> +	writel(address, port->reg_base + address_reg);
> +
> +	return port->reg_base + data_reg;
> +}
> +
>  struct pci_ops mt7621_pci_ops = {
> -	.read		= pci_config_read,
> -	.write		= pci_config_write,
> +	.map_bus	= mt7621_pcie_map_bus,
> +	.read		= pci_generic_config_read32,
> +	.write		= pci_generic_config_write32,
>  };
>  
>  static struct resource mt7621_res_pci_mem1;
>  static struct resource mt7621_res_pci_io1;
>  static struct pci_controller mt7621_controller = {
> -	.pci_ops	= &mt7621_pci_ops,
>  	.mem_resource	= &mt7621_res_pci_mem1,
>  	.io_resource	= &mt7621_res_pci_io1,
>  };
> @@ -489,10 +508,60 @@ void setup_cm_memory_region(struct resource *mem_resource)
>  	}
>  }
>  
> +static int mt7621_pcie_parse_dt(struct mt7621_pcie_port *port)
> +{
> +	struct device *dev = port->dev;
> +	struct device_node *node = dev->of_node;
> +	struct resource regs;
> +	const char *type;
> +	int err;
> +
> +	type = of_get_property(node, "device_type", NULL);
> +	if (!type || strcmp(type, "pci")) {
> +		dev_err(dev, "invalid \"device_type\" %s\n", type);
> +		return -EINVAL;
> +	}
> +
> +	err = of_address_to_resource(node, 0, &regs);
> +	if (err) {
> +		dev_err(dev, "missing \"reg\" property\n");
> +		return err;
> +	}
> +
> +	port->reg_base = devm_pci_remap_cfg_resource(dev, &regs);
> +	if (IS_ERR(port->reg_base))
> +		return PTR_ERR(port->reg_base);
> +
> +	return 0;
> +}
> +
>  static int mt7621_pci_probe(struct platform_device *pdev)
>  {
> +	struct device *dev = &pdev->dev;
> +	struct mt7621_pcie_port *port;
> +	struct pci_host_bridge *bridge;
> +	int err;
>  	unsigned long val = 0;
>  
> +	bridge = devm_pci_alloc_host_bridge(dev, sizeof(*port));
> +	if (!bridge)
> +		return -ENODEV;
> +
> +	port = pci_host_bridge_priv(bridge);
> +	port->dev = dev;
> +
> +	err = mt7621_pcie_parse_dt(port);
> +	if (err) {
> +		dev_err(dev, "Parsing DT failed\n");
> +		return err;
> +	}
> +
> +	bridge->dev.parent = dev;
> +	bridge->sysdata = port;
> +	bridge->ops = &mt7621_pci_ops;
> +	mt7621_controller.bus = bridge->bus;

bridge->bus hasn't been initialized yet, so it is NULL.

> +	mt7621_controller.bus->ops = bridge->ops;

So this is a NULL-pointer deref.

Maybe you need to call  pci_host_probe() somewhere? or
pci_scan_root_bus_bridge()?
Inserting either of those calls just after setting bridge->ops above
results in a hang, so something more subtle must been needed.

Thanks,
NeilBrown
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