Re: [PATCH v1 3/3] ARM64 LPC: update binding doc

From: Rongrong Zou <zourongrong@gmail.com>
To: Arnd Bergmann <arnd@arndb.de>, linux-arm-kernel@lists.infradead.org
Cc: Rongrong Zou <zourongrong@huawei.com>,
	devicetree@vger.kernel.org, benh@kernel.crashing.org,
	Corey Minyard <minyard@acm.org>,
	gregkh@linuxfoundation.org, Will Deacon <will.deacon@arm.com>,
	linux-kernel@vger.kernel.org, linuxarm@huawei.com,
	Catalin Marinas <catalin.marinas@arm.com>,
	liviu.dudau@arm.com
Subject: Re: [PATCH v1 3/3] ARM64 LPC: update binding doc
Date: Tue, 5 Jan 2016 00:04:19 +0800	[thread overview]
Message-ID: <568A9803.6050108@gmail.com> (raw)
In-Reply-To: <15026471.7nGZ0rWlIf@wuerfel>

在 2016/1/4 19:13, Arnd Bergmann 写道:
> On Sunday 03 January 2016 20:24:14 Rongrong Zou wrote:
>> 在 2015/12/31 23:00, Rongrong Zou 写道:
>>> 2015-12-31 22:40 GMT+08:00 Arnd Bergmann <arnd@arndb.de <mailto:arnd@arndb.de>>:
>>>   > On Thursday 31 December 2015 22:12:19 Rongrong Zou wrote:
>>>   > > 在 2015/12/30 17:06, Arnd Bergmann 写道:
>>>   > > > On Tuesday 29 December 2015 21:33:52 Rongrong Zou wrote:
>>>   >
>>>   > The DT sample above looks good in principle. I believe what you are missing
>>>   > here is code in your driver to scan the child nodes to create the platform
>>>   > devices. of_bus_isa_translate() should work with your definition here
>>>   > and create the correct IORESOURCE_IO resources. You don't have any MMIO
>>>   > resources, so the absence of a ranges property is ok. Maybe all you
>>>   > are missing is a call to of_platform_populate() or of_platform_bus_probe()?
>>>   >
>>>
>>> You are right. thanks, i'll try on test board .  if i get the correct result , the new patch
>>> will be sent later. By the way, it's my another email account use when i at home.
>>
>> I tried, and there need some additional changes.
>>
>> isa@a01b0000 {
>>
>> /*the node name should start with "isa", because of below definition
>> * static int of_bus_isa_match(struct device_node *np)
>> * {
>> *	return !strcmp(np->name, "isa");
>> * }
>
> Looks good. It would be nicer to match on device_type than on name,
> but this is ancient code and it's probably best not to touch it
> so we don't accidentally break some old SPARC or PPC system.
>
>> */
>> 	compatible = "low-pin-count";
>> 	device_type = "isa";
>> 	#address-cells = <2>;
>> 	#size-cells = <1>;
>> 	reg = <0x0 0xa01b0000 0x0 0x10000>;
>> 	ranges = <0x1 0x0 0x0 0x0 0x1000>;
>> /*
>> *  ranges is required, then i can get the IORESOURCE_IO <0xe4,4> from "reg = <0x1, 0x000000e4, 4>".
>> *
>> */
>> 	ipmi_0:ipmi@000000e4{
>> 		device_type = "ipmi";
>> 		compatible = "ipmi-bt";
>> 		reg = <0x1 0x000000e4 0x4>;
>> };
>>
>
> This looks wrong: the property above says that the I/O port range is
> translated to MMIO address 0x00000000 to 0x00010000, which is not
> true on your hardware. I think this needs to be changed in the code
> so the ranges property is not required for I/O ports.

Ranges property can set empty, but this means 1:1 translation. the I/O 
port range is translated to MMIO address 0x00000001 00000000 to 
0x00000001 00000004, it looks wrong else. I wonder if anyone get legacy 
I/O port resource from dts.

For ipmi driver, I can get I/O port resource by DMI rather than dts.

>
>> drivers\of\address.c
>> static int __of_address_to_resource(struct device_node *dev,
>>                   const __be32 *addrp, u64 size, unsigned int flags,
>>                   const char *name, struct resource *r)
>> {
>>           u64 taddr;
>>
>>           if ((flags & (IORESOURCE_IO | IORESOURCE_MEM)) == 0)
>>                   return -EINVAL;
>>           taddr = of_translate_address(dev, addrp);
>>           if (taddr == OF_BAD_ADDR)
>>                   return -EINVAL;
>>           memset(r, 0, sizeof(struct resource));
>>           if (flags & IORESOURCE_IO) {
>>                   unsigned long port;
>>
>> /*****************************************************************/
>> /*legacy port(< 0x1000) is reserved, and need no translation here*/
>> /*****************************************************************/
>>                   if(taddr + size < PCIBIOS_MIN_IO){
>>                           r->start = taddr;
>>                           r->end = taddr + size - 1;
>>                   }
>
> I don't like having a special case based on the address here,
> the same kind of hack might be needed for PCI I/O spaces in
> hardware that uses an indirect method like your LPC bus
> does, and the code above will not work on any LPC implementation
> that correctly multiplexes its I/O ports with the first PCI domain.
>
> I think it would be better to avoid translating the port into
> a physical address to start with just to translate it back into
> a port number, what we need instead is the offset between the
> bus specific port number and the linux port number. I've added
> Liviu to Cc, he wrote this code originally and may have some idea
> of how we could do that.
>
> 	Arnd
>