Re: [PATCH] RFC: add function for localbus address

[Grant Likely <grant.likely@linaro.org>]

On Tue,  2 Sep 2014 18:45:00 +0300, Stanimir Varbanov <svarbanov@mm-sol.com> wrote:
> Hi Grant,
> 
> I came down to this. Could you review? Is that
> implementation closer to the suggestion made by you.
> 
> ---
>  drivers/of/address.c       |   49 ++++++++++++++++++++++++++++++++++++++++++++
>  drivers/of/platform.c      |   20 ++++++++++++++---
>  include/linux/of_address.h |   19 +++++++++++++++++
>  3 files changed, 84 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/of/address.c b/drivers/of/address.c
> index e371825..86c2166 100644
> --- a/drivers/of/address.c
> +++ b/drivers/of/address.c
> @@ -601,6 +601,32 @@ const __be32 *of_get_address(struct device_node *dev, int index, u64 *size,
>  }
>  EXPORT_SYMBOL(of_get_address);
>  
> +const __be32 *of_get_localbus_address(struct device_node *np, int index,
> +				      u64 *size)
> +{
> +	struct device_node *root, *parent;
> +	const __be32 *ranges, *prop = NULL;
> +
> +	parent = of_get_parent(np);
> +	if (!parent)
> +		return NULL;
> +
> +	root = of_find_node_by_path("/");
> +
> +	if (parent == root) {
> +		of_node_put(parent);
> +		return NULL;
> +	}
> +
> +	ranges = of_get_property(parent, "ranges", NULL);
> +	of_node_put(parent);
> +
> +	if (!ranges)
> +		prop = of_get_address(np, index, size, NULL);
> +
> +	return prop;
> +}

So, the above doesn't make much sense to me. It looks like the function
merely decodes the local address, and the below function will stuff it
into a resource structure, but the tests for if the parent is root or
the parent has a ranges property are nonsensical. That shouldn't matter
for the functionality (except for automatically decoding them.. more
below)

> +
>  unsigned long __weak pci_address_to_pio(phys_addr_t address)
>  {
>  	if (address > IO_SPACE_LIMIT)
> @@ -665,6 +691,29 @@ int of_address_to_resource(struct device_node *dev, int index,
>  }
>  EXPORT_SYMBOL_GPL(of_address_to_resource);
>  
> +int of_localbus_address_to_resource(struct device_node *dev, int index,
> +				    struct resource *r)
> +{
> +	const char *name = NULL;
> +	const __be32 *addrp;
> +	u64 size;
> +
> +	addrp = of_get_localbus_address(dev, index, &size);
> +	if (!addrp)
> +		return -EINVAL;
> +
> +	of_property_read_string_index(dev, "reg-names", index, &name);
> +
> +	memset(r, 0, sizeof(*r));
> +	r->start = be32_to_cpup(addrp);
> +	r->end = r->start + size - 1;
> +	r->flags = IORESOURCE_REG;

This is problematic. A resource is created, but there is absolutely no
indication that the resource represents a localbus address instead of a
CPU address. platform_device reg resources represent CPU addresses.
Trying to overload it will cause confusion in drivers.

> +	r->name = name ? name : dev->full_name;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(of_localbus_address_to_resource);
> +
>  struct device_node *of_find_matching_node_by_address(struct device_node *from,
>  					const struct of_device_id *matches,
>  					u64 base_address)
> diff --git a/drivers/of/platform.c b/drivers/of/platform.c
> index 0197725..36dcbd7 100644
> --- a/drivers/of/platform.c
> +++ b/drivers/of/platform.c
> @@ -106,8 +106,9 @@ struct platform_device *of_device_alloc(struct device_node *np,
>  				  struct device *parent)
>  {
>  	struct platform_device *dev;
> -	int rc, i, num_reg = 0, num_irq;
> +	int rc, i, num_reg = 0, num_localbus_reg = 0, num_irq;
>  	struct resource *res, temp_res;
> +	int num_resources;
>  
>  	dev = platform_device_alloc("", -1);
>  	if (!dev)
> @@ -116,22 +117,33 @@ struct platform_device *of_device_alloc(struct device_node *np,
>  	/* count the io and irq resources */
>  	while (of_address_to_resource(np, num_reg, &temp_res) == 0)
>  		num_reg++;
> +
> +	while (of_localbus_address_to_resource(np,
> +					num_localbus_reg, &temp_res) == 0)
> +		num_localbus_reg++;
> +

No, I don't support doing this. The moment a platform_driver depends on
a local bus address it is doing something special. It needs to decode
its own address in that case, which it can easily do.

Any platform_driver that interprets a IORESOURCE_REG as a localbus
address instead of a CPU address is *BROKEN*. It should be changed to
either decode the address itself, of a new bus type should be created
that can make its own decisions about what address resources mean.

I realize that you want to reuse the platform populate functionality in
this case. We can refactor some of that code to make it usable for
customized platform_bus_type instances.

g.