linux-kernel - Re: [PATCH] RFC: add function for localbus address

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Date:	Mon, 08 Sep 2014 13:22:44 -0700
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Grant Likely <grant.likely@...aro.org>,
	Stanimir Varbanov <svarbanov@...sol.com>
CC:	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
	Rob Herring <robherring2@...il.com>,
	Rob Herring <rob.herring@...aro.org>,
	Arnd Bergmann <arnd@...db.de>,
	Lee Jones <lee.jones@...aro.org>,
	Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH] RFC: add function for localbus address

Adding Mark Brown who finished off introducing IORESOURCE_REG.

On 09/08/14 07:52, Grant Likely wrote:
> On Tue,  2 Sep 2014 18:45:00 +0300, Stanimir Varbanov <svarbanov@...sol.com> wrote:
>> +
>>  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.

Where is this described? From the commit text that introduces
IORESOURCE_REG I see:

"Currently a bunch of I2C/SPI MFD drivers are using IORESOURCE_IO for
register address ranges. Since this causes some confusion due to the
primary use of this resource type for PCI/ISA I/O ports create a new
resource type IORESOURCE_REG."

And the comment next to the #define says "Register offsets". I don't see
anywhere where it mentions these are CPU addresses. Certainly the
current IORESOURCE_REG users aren't CPU addresses because they're
SPI/I2C device drivers.

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
hosted by The Linux Foundation

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