Subject: Re: [PATCH v7 2/3] of/pci: Provide support for parsing PCI DT ranges property

From: Grant Likely <[email-masked]>
Date: Thu, 18 Apr 2013 14:44:01 +0100

On Tue, 16 Apr 2013 11:18:27 +0100, Andrew Murray <[email-masked]> wrote:
> This patch factors out common implementation patterns to reduce overall kernel
> code and provide a means for host bridge drivers to directly obtain struct
> resources from the DT's ranges property without relying on architecture specific
> DT handling. This will make it easier to write archiecture independent host bridge
> drivers and mitigate against further duplication of DT parsing code.
> 
> This patch can be used in the following way:
> 
> 	struct of_pci_range_parser parser;
> 	struct of_pci_range range;
> 
> 	if (of_pci_range_parser(&parser, np))
> 		; //no ranges property
> 
> 	for_each_of_pci_range(&parser, &range) {
> 
> 		/*
> 			directly access properties of the address range, e.g.:
> 			range.pci_space, range.pci_addr, range.cpu_addr,
> 			range.size, range.flags
> 
> 			alternatively obtain a struct resource, e.g.:
> 			struct resource res;
> 			of_pci_range_to_resource(&range, np, &res);
> 		*/
> 	}
> 
> Additionally the implementation takes care of adjacent ranges and merges them
> into a single range (as was the case with powerpc and microblaze).
> 
> Signed-off-by: Andrew Murray <[email-masked]>
> Signed-off-by: Liviu Dudau <[email-masked]>
> Signed-off-by: Thomas Petazzoni <[email-masked]>
> Reviewed-by: Rob Herring <[email-masked]>
> Tested-by: Thomas Petazzoni <[email-masked]>
> Tested-by: Linus Walleij <[email-masked]>

Acked-by: Grant Likely <[email-masked]>

But comments below...

> ---
>  drivers/of/address.c       |   67 ++++++++++++++++++++++++++
>  drivers/of/of_pci.c        |  113 ++++++++++++++++----------------------------
>  include/linux/of_address.h |   46 ++++++++++++++++++
>  3 files changed, 154 insertions(+), 72 deletions(-)
> 
> diff --git a/drivers/of/address.c b/drivers/of/address.c
> index 04da786..6eec70c 100644
> --- a/drivers/of/address.c
> +++ b/drivers/of/address.c
> @@ -227,6 +227,73 @@ int of_pci_address_to_resource(struct device_node *dev, int bar,
>  	return __of_address_to_resource(dev, addrp, size, flags, NULL, r);
>  }
>  EXPORT_SYMBOL_GPL(of_pci_address_to_resource);
> +
> +int of_pci_range_parser(struct of_pci_range_parser *parser,
> +			struct device_node *node)
> +{
> +	const int na = 3, ns = 2;
> +	int rlen;
> +
> +	parser->node = node;
> +	parser->pna = of_n_addr_cells(node);
> +	parser->np = parser->pna + na + ns;
> +
> +	parser->range = of_get_property(node, "ranges", &rlen);
> +	if (parser->range == NULL)
> +		return -ENOENT;
> +
> +	parser->end = parser->range + rlen / sizeof(__be32);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(of_pci_range_parser);

"of_pci_range_parser_init" would be a clearer name

> +struct of_pci_range *of_pci_process_ranges(struct of_pci_range_parser *parser,
> +						struct of_pci_range *range)

Similarly, "of_pci_range_parser_one" would be more consistent.

> +{
> +	const int na = 3, ns = 2;
> +
> +	if (!range)
> +		return NULL;
> +
> +	if (!parser->range || parser->range + parser->np > parser->end)
> +		return NULL;
> +
> +	range->pci_space = parser->range[0];
> +	range->flags = of_bus_pci_get_flags(parser->range);
> +	range->pci_addr = of_read_number(parser->range + 1, ns);
> +	range->cpu_addr = of_translate_address(parser->node,
> +				parser->range + na);
> +	range->size = of_read_number(parser->range + parser->pna + na, ns);
> +
> +	parser->range += parser->np;
> +
> +	/* Now consume following elements while they are contiguous */
> +	while (parser->range + parser->np <= parser->end) {
> +		u32 flags, pci_space;
> +		u64 pci_addr, cpu_addr, size;
> +
> +		pci_space = be32_to_cpup(parser->range);
> +		flags = of_bus_pci_get_flags(parser->range);
> +		pci_addr = of_read_number(parser->range + 1, ns);
> +		cpu_addr = of_translate_address(parser->node,
> +				parser->range + na);
> +		size = of_read_number(parser->range + parser->pna + na, ns);
> +
> +		if (flags != range->flags)
> +			break;
> +		if (pci_addr != range->pci_addr + range->size ||
> +		    cpu_addr != range->cpu_addr + range->size)
> +			break;
> +
> +		range->size += size;
> +		parser->range += parser->np;
> +	}
> +
> +	return range;
> +}
> +EXPORT_SYMBOL_GPL(of_pci_process_ranges);
> +
>  #endif /* CONFIG_PCI */
>  
>  /*
> diff --git a/drivers/of/of_pci.c b/drivers/of/of_pci.c
> index 1626172..e5ab604 100644
> --- a/drivers/of/of_pci.c
> +++ b/drivers/of/of_pci.c
> @@ -2,6 +2,7 @@
>  #include <linux/export.h>
>  #include <linux/of.h>
>  #include <linux/of_pci.h>
> +#include <linux/of_address.h>
>  #include <asm/prom.h>
>  
>  #if defined(CONFIG_PPC32) || defined(CONFIG_PPC64) || defined(CONFIG_MICROBLAZE)
> @@ -82,67 +83,43 @@ EXPORT_SYMBOL_GPL(of_pci_find_child_device);
>  void pci_process_bridge_OF_ranges(struct pci_controller *hose,
>  				  struct device_node *dev, int primary)
>  {
> -	const u32 *ranges;
> -	int rlen;
> -	int pna = of_n_addr_cells(dev);
> -	int np = pna + 5;
>  	int memno = 0, isa_hole = -1;
> -	u32 pci_space;
> -	unsigned long long pci_addr, cpu_addr, pci_next, cpu_next, size;
>  	unsigned long long isa_mb = 0;
>  	struct resource *res;
> +	struct of_pci_range range;
> +	struct of_pci_range_parser parser;
> +	u32 res_type;
>  
>  	pr_info("PCI host bridge %s %s ranges:\n",
>  	       dev->full_name, primary ? "(primary)" : "");
>  
> -	/* Get ranges property */
> -	ranges = of_get_property(dev, "ranges", &rlen);
> -	if (ranges == NULL)
> +	/* Check for ranges property */
> +	if (of_pci_range_parser(&parser, dev))
>  		return;
>  
> -	/* Parse it */
>  	pr_debug("Parsing ranges property...\n");
> -	while ((rlen -= np * 4) >= 0) {
> +	for_each_of_pci_range(&parser, &range) {
>  		/* Read next ranges element */
> -		pci_space = ranges[0];
> -		pci_addr = of_read_number(ranges + 1, 2);
> -		cpu_addr = of_translate_address(dev, ranges + 3);
> -		size = of_read_number(ranges + pna + 3, 2);

Tip: the diff on this function would be a whole lot simpler if the
above locals were kept, but updated from the ranges structure. Not at
all a big problem, but it is something that makes changes like this
easier to review. The removal of the locals could also be split into a
separate patch to end up with the same result.

> -
> -		pr_debug("pci_space: 0x%08x pci_addr:0x%016llx ",
> -				pci_space, pci_addr);
> -		pr_debug("cpu_addr:0x%016llx size:0x%016llx\n",
> -					cpu_addr, size);
> -
> -		ranges += np;
> +		pr_debug("pci_space: 0x%08x pci_addr: 0x%016llx ",
> +				range.pci_space, range.pci_addr);
> +		pr_debug("cpu_addr: 0x%016llx size: 0x%016llx\n",
> +				range.cpu_addr, range.size);

Nit: the patch changed whitespace on the pr_debug() statements, so even
though the first line of each is identical, they look different in the
patch.

>  
>  		/* If we failed translation or got a zero-sized region
>  		 * (some FW try to feed us with non sensical zero sized regions
>  		 * such as power3 which look like some kind of attempt
>  		 * at exposing the VGA memory hole)
>  		 */
> -		if (cpu_addr == OF_BAD_ADDR || size == 0)
> +		if (range.cpu_addr == OF_BAD_ADDR || range.size == 0)
>  			continue;

Can this also be rolled into the parsing iterator?

>  
> -		/* Now consume following elements while they are contiguous */
> -		for (; rlen >= np * sizeof(u32);
> -		     ranges += np, rlen -= np * 4) {
> -			if (ranges[0] != pci_space)
> -				break;
> -			pci_next = of_read_number(ranges + 1, 2);
> -			cpu_next = of_translate_address(dev, ranges + 3);
> -			if (pci_next != pci_addr + size ||
> -			    cpu_next != cpu_addr + size)
> -				break;
> -			size += of_read_number(ranges + pna + 3, 2);
> -		}
> -
>  		/* Act based on address space type */
>  		res = NULL;
> -		switch ((pci_space >> 24) & 0x3) {
> -		case 1:		/* PCI IO space */
> +		res_type = range.flags & IORESOURCE_TYPE_BITS;
> +		if (res_type == IORESOURCE_IO) {

Why the change from switch() to an if/else if sequence?

But those are mostly nitpicks. If this is deferred to v3.10 then I would
suggest fixing them up and posting for another round of review.

g.